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From Michael Pearce <Michael.Pea...@ig.com>
Subject Re: [DISCUSS] KIP-82 - Add Record Headers
Date Tue, 21 Feb 2017 17:10:28 GMT
This works whilst no other feature needs similar. I prefer to keep it contained/encapsulated it then allows the bytes of the headers to also be copied transferred as one without any parsing what so ever, but if you really feel strongly on the below ill go with it, just want to flag this concern.

Btw, the below notation seems to be different to the notation used in previous kips like kip-32 which I took the notation from, where the length of the following bytes for byte arrays is clearly defined. So im 100% on what you propose could you define it in this original styled notation?


On 20/02/2017, 19:58, "Jason Gustafson" <jason@confluent.io> wrote:

    Hey Jun, that's a good thought. Maybe then the full schema could look like
    this:

    Record =>
      Length => uintVar
      Attributes => int8
      TimestampDelta => intVar
      OffsetDelta => uintVar
      Key => bytes
      Value => bytes
      Headers => [HeaderKey HeaderValue]
        HeaderKey => string
        HeaderValue => bytes

    (where the bytes and string type use a variable length size field)

    Does that work for you, Michael?

    -Jason

    On Mon, Feb 20, 2017 at 9:28 AM, Jun Rao <jun@confluent.io> wrote:

    > Regarding the overhead of skipping the headers in the message. Another way
    > could be to add the headers at the end of the message after the value part.
    > This way, there is no need to skip the headers unless you really need it.
    > This will allow us to represent the headers explicitly as an array of
    > key/value pairs without the skipping overhead when headers are not needed.
    >
    > Thanks,
    >
    > Jun
    >
    > On Sun, Feb 19, 2017 at 7:13 PM, Jason Gustafson <jason@confluent.io>
    > wrote:
    >
    > > Michael,
    > >
    > > Here's a link to the branch with the message format changes:
    > > https://github.com/confluentinc/kafka/tree/exactly-once-message-format.
    > > The
    > > class to modify to add headers is EosLogRecord (name will definitely
    > change
    > > prior to merging in trunk). This branch uses attributes to indicate null
    > > key and value. I really don't have a strong preference for or against
    > this
    > > as long as we're consistent. I do feel it's kind of a pity to need the
    > > signed version of the varint just to be able to indicate null. For
    > headers,
    > > it's an easier call because we don't actually need to represent null
    > > headers (using size zero will work fine).
    > >
    > > -Jason
    > >
    > > On Sun, Feb 19, 2017 at 5:38 PM, Michael Pearce <Michael.Pearce@ig.com>
    > > wrote:
    > >
    > > > We can make it, implement Iterable<Header>, no concerns on this.
    > > >
    > > > Ive noted this on the KIP.
    > > >
    > > >
    > > > On 20/02/2017, 01:24, "Michael Pearce" <Michael.Pearce@ig.com> wrote:
    > > >
    > > >     Btw Jason, can you share the branch with the VarInts helper/util
    > > class
    > > > that KIP-98 will be introducing and also will have the current modified
    > > > (key and value lengths) message, so we can look at, thanks.
    > > >
    > > >     On 20/02/2017, 01:11, "Michael Pearce" <Michael.Pearce@ig.com>
    > > wrote:
    > > >
    > > >         RE “ProducerRecord and ConsumerRecord are immutable
    > currently”. I
    > > > beg to differ on this, if I set a byte[] as my value of my record, I
    > can
    > > > later call value() and then alter the bytes in the array. As such it is
    > > > very much mutable.
    > > >
    > > >         Headers also will anyhow by nature be mutable on produce, as
    > you
    > > > add to them.
    > > >
    > > >
    > > >         On 20/02/2017, 00:22, "Jason Gustafson" <jason@confluent.io>
    > > > wrote:
    > > >
    > > >             Re; having a dedicated Headers object. I think it makes
    > > sense.
    > > > Maybe it
    > > >             could implement Iterable<Header>?
    > > >
    > > >             One thing I'm not too sure about is mutability. Both the
    > > > ProducerRecord and
    > > >             ConsumerRecord are immutable currently. It would be nice to
    > > > keep it that
    > > >             way. Perhaps Headers could itself be immutable and passed
    > > > through the
    > > >             constructors?
    > > >
    > > >             Just going through how this is,  I don’t believe this would
    > > > provide much
    > > >             > saving. If issue trying to resolve is around
    > object/garbage
    > > > creation of
    > > >             > Map.Entry objects.
    > > >
    > > >
    > > >             It's definitely better because we only allocate the space
    > we
    > > > will use, but
    > > >             I assume most of the actual memory cost is in the header
    > data
    > > > itself which
    > > >             we can't do much about. Maybe we can start with the simple
    > > > array
    > > >             representation and optimize from there after we find it's
    > > > worthwhile to do
    > > >             so? If we use the Headers object, we can change this later
    > > > without breaking
    > > >             the API.
    > > >
    > > >             -Jason
    > > >
    > > >             On Sun, Feb 19, 2017 at 2:39 PM, radai <
    > > > radai.rosenblatt@gmail.com> wrote:
    > > >
    > > >             > "(By the way, doesn't it feel a bit odd that we seem to
    > be
    > > > designing a
    > > >             > feature which is optimized for people not using?)"
    > > >             >
    > > >             > very. this (i claim :-) ) is the result of very intense
    > > > opposition to the
    > > >             > usefulness of the feature early on, and not a real design
    > > > goal
    > > >             >
    > > >             > On Sun, Feb 19, 2017 at 2:11 PM, Michael Pearce <
    > > > Michael.Pearce@ig.com>
    > > >             > wrote:
    > > >             >
    > > >             > > Whilst if having an array of a Header[] would mean
    > > getting
    > > > this through,
    > > >             > > im happy changing this, as already done.
    > > >             > >
    > > >             > > Just going through how this is,  I don’t believe this
    > > > would provide much
    > > >             > > saving. If issue trying to resolve is around
    > > > object/garbage creation of
    > > >             > > Map.Entry objects.
    > > >             > >
    > > >             > > All you’re doing here is replacing the equiv of a
    > > > HashMap.Node
    > > >             > (Map.Entry)
    > > >             > > which simply holds reference to key and value objects
    > > with
    > > > a custom
    > > >             > variant.
    > > >             > >
    > > >             > >
    > > >             > >
    > > >             > >
    > > >             > >
    > > >             > > On 19/02/2017, 20:22, "Michael Pearce" <
    > > > Michael.Pearce@ig.com> wrote:
    > > >             > >
    > > >             > >     On point 1 & 2 Ive updated KIP to show varints (and
    > > > removed the bit
    > > >             > > flag). (on the assumption KIP 98 is getting the
    > agreement
    > > > the protocol is
    > > >             > > moving from int32 to varInts as standard)
    > > >             > >
    > > >             > >     On point 3 ive updated to use an array of Header
    > > > class, instead of a
    > > >             > > MultiMap in the Headers class object
    > > >             > >
    > > >             > >
    > > >             > >
    > > >             > >     On 19/02/2017, 20:06, "Michael Pearce" <
    > > > Michael.Pearce@ig.com>
    > > >             > wrote:
    > > >             > >
    > > >             > >         On points 1 and 2 I agree.
    > > >             > >
    > > >             > >         This also affects kip-98, I should expect this
    > > > resolved before
    > > >             > > that vote also passes. If it is accepted there (I’m
    > > > assuming this is
    > > >             > > getting discussed on that KIP? As you’re driving the
    > move
    > > > to VarInts), I
    > > >             > am
    > > >             > > happy to make this KIP will simply follow suit to
    > > whatever
    > > > is agreed in
    > > >             > > KIP-98.
    > > >             > >
    > > >             > >         On 3) Agreed this is a simpler form, as long as
    > > no
    > > > one is
    > > >             > > expecting hashmap lookup performance ( O(1) ), I still
    > > > would prefer an
    > > >             > > encapsulated class, so if we find that holding it as an
    > > > array in future
    > > >             > is
    > > >             > > causing some perf issues, the internals are not exposed
    > > to
    > > > end users,
    > > >             > > allowing the internal structure to move to a map.
    > > >             > >
    > > >             > >         Can we compromise on?
    > > >             > >
    > > >             > >         class ConsumerRecord<K, V> {
    > > >             > >                 K key;
    > > >             > >                 V value;
    > > >             > >                 Headers headers;
    > > >             > >             }
    > > >             > >
    > > >             > >             class Headers {
    > > >             > >               Header[] headers;
    > > >             > >
    > > >             > >               add(String key, byte[] value)
    > > >             > >               Collection<byte[]> get(String key)
    > > >             > >             }
    > > >             > >
    > > >             > >             class Header {
    > > >             > >               String key;
    > > >             > >               byte[] value;
    > > >             > >             }
    > > >             > >
    > > >             > >
    > > >             > >
    > > >             > >         On 19/02/2017, 18:54, "Jason Gustafson" <
    > > > jason@confluent.io>
    > > >             > > wrote:
    > > >             > >
    > > >             > >             >
    > > >             > >             > headers dont "leak" into application
    > code.
    > > > they are useful
    > > >             > > to application
    > > >             > >             > code as well.
    > > >             > >
    > > >             > >
    > > >             > >             This is exactly what I have been trying to
    > > get
    > > > at. The use
    > > >             > > cases documented
    > > >             > >             here are middleware:
    > > >             > >             https://cwiki.apache.org/
    > > > confluence/display/KAFKA/A+
    > > >             > > Case+for+Kafka+Headers.
    > > >             > >             If headers are intended for the application
    > > > space as well,
    > > >             > the
    > > >             > > document
    > > >             > >             should be updated accordingly so that it is
    > > an
    > > > explicit
    > > >             > design
    > > >             > > goal and not
    > > >             > >             an unfortunate design byproduct. There may
    > be
    > > > some
    > > >             > > disagreement on whether
    > > >             > >             it _should_ be a design goal, but it may
    > not
    > > > matter much
    > > >             > since
    > > >             > > the current
    > > >             > >             interceptor API is probably insufficient
    > for
    > > > middleware
    > > >             > > applications (I
    > > >             > >             haven't thought of a way to do this that
    > > isn't
    > > > cumbersome).
    > > >             > >
    > > >             > >             That aside, the three unresolved points for
    > > me
    > > > are the
    > > >             > > following:
    > > >             > >
    > > >             > >             1. The use of varints. As a one-off for use
    > > > only with record
    > > >             > > headers, the
    > > >             > >             case was weak, but if we are using them
    > > > throughout the
    > > >             > message
    > > >             > > format, then
    > > >             > >             we should do so here as well. The
    > additional
    > > > complexity is
    > > >             > > minimal and
    > > >             > >             early performance testing fully justifies
    > > > their use.
    > > >             > >
    > > >             > >             2. If varints are used, the case for using
    > > > attributes to
    > > >             > > indicate null
    > > >             > >             headers also becomes weak. We only add one
    > > > additional byte in
    > > >             > > each message
    > > >             > >             if there are no headers. Whatever the case,
    > > > let us be
    > > >             > > consistent with how
    > > >             > >             we treat null keys and values.
    > > >             > >
    > > >             > >             3. We have apparently agreed that the
    > broker
    > > > will validate
    > > >             > > headers (please
    > > >             > >             add this to the KIP). That being the case,
    > I
    > > > would prefer to
    > > >             > > use Kafka's
    > > >             > >             conventional format for arrays. The
    > downside
    > > > is that it takes
    > > >             > > more work to
    > > >             > >             skip over the headers on the consumer,
    > though
    > > > it's unclear if
    > > >             > > the cost
    > > >             > >             would matter in practice. Some concern was
    > > > previously
    > > >             > > expressed about the
    > > >             > >             allocation of maps. An alternative would be
    > > to
    > > > use arrays,
    > > >             > i.e.
    > > >             > >
    > > >             > >             class ConsumerRecord<K, V> {
    > > >             > >                 K key;
    > > >             > >                 V value;
    > > >             > >                 Header[] headers;
    > > >             > >             }
    > > >             > >
    > > >             > >             class Header {
    > > >             > >               String key;
    > > >             > >               byte[] value;
    > > >             > >             }
    > > >             > >
    > > >             > >             This would work nicely with the
    > conventional
    > > > array format and
    > > >             > > my guess is
    > > >             > >             it would obviate the need do any lazy
    > > > initialization. If we
    > > >             > > use the map as
    > > >             > >             is currently documented, then it is
    > possible
    > > > with either
    > > >             > > representation to
    > > >             > >             slice the headers and initialize them
    > lazily.
    > > > Either way, it
    > > >             > > might be a
    > > >             > >             good idea to use a separate object to
    > > > represent the headers
    > > >             > in
    > > >             > > case we need
    > > >             > >             to modify it in the future in some way.
    > > >             > >
    > > >             > >             (By the way, doesn't it feel a bit odd that
    > > we
    > > > seem to be
    > > >             > > designing a
    > > >             > >             feature which is optimized for people not
    > > > using?)
    > > >             > >
    > > >             > >
    > > >             > >             If we can resolve these points, then at
    > least
    > > > you will get my
    > > >             > > vote.
    > > >             > >
    > > >             > >             Thanks,
    > > >             > >             Jason
    > > >             > >
    > > >             > >             On Sun, Feb 19, 2017 at 7:30 AM, radai <
    > > >             > > radai.rosenblatt@gmail.com> wrote:
    > > >             > >
    > > >             > >             > headers dont "leak" into application
    > code.
    > > > they are useful
    > > >             > > to application
    > > >             > >             > code as well.
    > > >             > >             > IIUC samze currently has headers "in-V"
    > and
    > > > would just
    > > >             > > switch over to kafka
    > > >             > >             > headers if they exist.
    > > >             > >             > im sure plenty of other users of kafka
    > > would
    > > > have a use for
    > > >             > > headers.
    > > >             > >             > im pretty sure use cases exist around
    > > > shuffling data
    > > >             > > into/out-of kafka
    > > >             > >             > (kafka connect or equivalent) where
    > > metadata
    > > > from one end
    > > >             > > could copied over
    > > >             > >             > to the other (S3, for example uses http
    > > > headers for
    > > >             > > user-accessible
    > > >             > >             > metadata). it will be kafka client code
    > > > getting/setting
    > > >             > > those headers. not
    > > >             > >             > an interceptor.
    > > >             > >             >
    > > >             > >             > On Fri, Feb 17, 2017 at 1:41 PM, Michael
    > > > Pearce <
    > > >             > > Michael.Pearce@ig.com>
    > > >             > >             > wrote:
    > > >             > >             >
    > > >             > >             > > For APM single event tracing, need
    > access
    > > > to the header
    > > >             > at
    > > >             > > the point of
    > > >             > >             > > processing on the processing thread.
    > > >             > >             > >
    > > >             > >             > > As such interceptors will not work/be
    > > > suitable for these,
    > > >             > > due to the fact
    > > >             > >             > > they act on the ConsumerRecords as a
    > > > batch, before the
    > > >             > > handling thread
    > > >             > >             > can
    > > >             > >             > > split out and process per message which
    > > is
    > > > the point
    > > >             > these
    > > >             > > tools will
    > > >             > >             > need
    > > >             > >             > > to continue to transaction tracing.
    > > >             > >             > >
    > > >             > >             > > Like wise tools and infra pieces will
    > > need
    > > > access to the
    > > >             > > message outside
    > > >             > >             > > the interceptor realm.
    > > >             > >             > >
    > > >             > >             > >
    > > >             > >             > >
    > > >             > >             > > On 17/02/2017, 21:26, "Jason
    > Gustafson" <
    > > >             > > jason@confluent.io> wrote:
    > > >             > >             > >
    > > >             > >             > >     >
    > > >             > >             > >     > That’s exactly what we’re doing
    > the
    > > > headers are a
    > > >             > > slice of bytes,
    > > >             > >             > > which
    > > >             > >             > >     > then gets parsed later if needed,
    > > or
    > > > can be parsed
    > > >             > > right away, the
    > > >             > >             > > headers
    > > >             > >             > >     > is part of the protocol, so can
    > > > still be validated
    > > >             > > if wanted.
    > > >             > >             > >     > If you had a header count then
    > you
    > > > would have to go
    > > >             > > through each
    > > >             > >             > > header
    > > >             > >             > >     > key and value length value to
    > work
    > > > out how much to
    > > >             > > skip to get to
    > > >             > >             > > say the
    > > >             > >             > >     > value or any future component in
    > > the
    > > > message after
    > > >             > > the headers.
    > > >             > >             > > Having it
    > > >             > >             > >     > as a byte[] with length value
    > makes
    > > > this a lot
    > > >             > > easier to skip.
    > > >             > >             > >
    > > >             > >             > >
    > > >             > >             > >     So the broker will parse the
    > headers
    > > > and validate
    > > >             > > them. Good. The
    > > >             > >             > only
    > > >             > >             > >     reason remaining that I can see to
    > > > leave the headers
    > > >             > > as a byte array
    > > >             > >             > > is to
    > > >             > >             > >     make it easier for the client to
    > skip
    > > > past them. Are
    > > >             > > we sure this is
    > > >             > >             > > not
    > > >             > >             > >     premature optimization? Are there
    > any
    > > > performance
    > > >             > > results which show
    > > >             > >             > > that
    > > >             > >             > >     this is worthwhile?
    > > >             > >             > >
    > > >             > >             > >     What’s the issue with exposing a
    > > > method getHeaders on
    > > >             > > the
    > > >             > >             > > producer/consumer
    > > >             > >             > >     > record? It doesn’t break
    > anything.
    > > > We don’t need
    > > >             > any
    > > >             > > special
    > > >             > >             > version.
    > > >             > >             > >
    > > >             > >             > >
    > > >             > >             > >     See my previous explanation. What I
    > > am
    > > > trying to
    > > >             > > resist is the
    > > >             > >             > headers
    > > >             > >             > >     becoming a general
    > application-level
    > > > facility. The
    > > >             > > primary use case
    > > >             > >             > as
    > > >             > >             > > far
    > > >             > >             > >     as I can tell is middleware, which
    > is
    > > > the use case
    > > >             > > that the
    > > >             > >             > > interceptors
    > > >             > >             > >     are providing.
    > > >             > >             > >
    > > >             > >             > >     Current batch consumer model and
    > > > consumer
    > > >             > interceptors
    > > >             > > don’t work
    > > >             > >             > where
    > > >             > >             > >     > headers need to be acted on at
    > per
    > > > message level at
    > > >             > > time of
    > > >             > >             > > processing,
    > > >             > >             > >     > very case is APM (the core one),
    > > > where the header
    > > >             > > value is used to
    > > >             > >             > > continue
    > > >             > >             > >     > tracing.
    > > >             > >             > >
    > > >             > >             > >
    > > >             > >             > >     I still don't understand the point
    > > > about batching.
    > > >             > The
    > > >             > > consumer
    > > >             > >             > > records are
    > > >             > >             > >     exposed as a batch in the consumer
    > > > interceptor, but
    > > >             > > you can still
    > > >             > >             > > iterate
    > > >             > >             > >     them individually. It is no
    > different
    > > > for the
    > > >             > consumer
    > > >             > > API itself.
    > > >             > >             > >
    > > >             > >             > >     -Jason
    > > >             > >             > >
    > > >             > >             > >     On Fri, Feb 17, 2017 at 12:48 PM,
    > > > Michael Pearce <
    > > >             > >             > > Michael.Pearce@ig.com>
    > > >             > >             > >     wrote:
    > > >             > >             > >
    > > >             > >             > >     > Re:
    > > >             > >             > >     >
    > > >             > >             > >     > “    The point about creation of
    > > > maps seems
    > > >             > > orthogonal. We can
    > > >             > >             > still
    > > >             > >             > >     > represent
    > > >             > >             > >     >     the headers as a slice of
    > bytes
    > > > until the time
    > > >             > > it is accessed.”
    > > >             > >             > >     >
    > > >             > >             > >     > That’s exactly what we’re doing
    > the
    > > > headers are a
    > > >             > > slice of bytes,
    > > >             > >             > > which
    > > >             > >             > >     > then gets parsed later if needed,
    > > or
    > > > can be parsed
    > > >             > > right away, the
    > > >             > >             > > headers
    > > >             > >             > >     > is part of the protocol, so can
    > > > still be validated
    > > >             > > if wanted.
    > > >             > >             > >     >
    > > >             > >             > >     > If you had a header count then
    > you
    > > > would have to go
    > > >             > > through each
    > > >             > >             > > header
    > > >             > >             > >     > key and value length value to
    > work
    > > > out how much to
    > > >             > > skip to get to
    > > >             > >             > > say the
    > > >             > >             > >     > value or any future component in
    > > the
    > > > message after
    > > >             > > the headers.
    > > >             > >             > > Having it
    > > >             > >             > >     > as a byte[] with length value
    > makes
    > > > this a lot
    > > >             > > easier to skip.
    > > >             > >             > >     >
    > > >             > >             > >     >
    > > >             > >             > >     > On 17/02/2017, 20:37, "Michael
    > > > Pearce" <
    > > >             > > Michael.Pearce@ig.com>
    > > >             > >             > > wrote:
    > > >             > >             > >     >
    > > >             > >             > >     >     What’s the issue with
    > exposing
    > > a
    > > > method
    > > >             > > getHeaders on the
    > > >             > >             > >     > producer/consumer record? It
    > > doesn’t
    > > > break
    > > >             > anything.
    > > >             > > We don’t need
    > > >             > >             > > any
    > > >             > >             > >     > special version.
    > > >             > >             > >     >
    > > >             > >             > >     >     Current batch consumer model
    > > and
    > > > consumer
    > > >             > > interceptors don’t
    > > >             > >             > work
    > > >             > >             > >     > where headers need to be acted on
    > > at
    > > > per message
    > > >             > > level at time of
    > > >             > >             > >     > processing, very case is APM (the
    > > > core one), where
    > > >             > > the header value
    > > >             > >             > > is used
    > > >             > >             > >     > to continue tracing. JMS/HTTP etc
    > > > all expose these,
    > > >             > > without issues.
    > > >             > >             > > I would
    > > >             > >             > >     > NOT want to lock this down to
    > only
    > > > be usable
    > > >             > > accessible via
    > > >             > >             > > interceptors,
    > > >             > >             > >     > as we’d fail on one of the main
    > > > goals.
    > > >             > >             > >     >
    > > >             > >             > >     >     Regards
    > > >             > >             > >     >     Mike
    > > >             > >             > >     >
    > > >             > >             > >     >
    > > >             > >             > >     >
    > > >             > >             > >     >
    > > >             > >             > >     >     On 17/02/2017, 20:21, "Jason
    > > > Gustafson" <
    > > >             > > jason@confluent.io>
    > > >             > >             > > wrote:
    > > >             > >             > >     >
    > > >             > >             > >     >         The point about creation
    > of
    > > > maps seems
    > > >             > > orthogonal. We can
    > > >             > >             > > still
    > > >             > >             > >     > represent
    > > >             > >             > >     >         the headers as a slice of
    > > > bytes until the
    > > >             > > time it is
    > > >             > >             > > accessed.
    > > >             > >             > >     >
    > > >             > >             > >     >
    > > >             > >             > >     >         > Yes exactly we have
    > > access
    > > > to the records
    > > >             > > thus why the
    > > >             > >             > > header
    > > >             > >             > >     > should be
    > > >             > >             > >     >         > accessible via it and
    > not
    > > > hidden for only
    > > >             > > interceptors to
    > > >             > >             > > access.
    > > >             > >             > >     >
    > > >             > >             > >     >
    > > >             > >             > >     >         As explained above, the
    > > > point is to make
    > > >             > the
    > > >             > > intended usage
    > > >             > >             > > clear.
    > > >             > >             > >     >         Applications should
    > > continue
    > > > to rely on the
    > > >             > > key/value
    > > >             > >             > fields
    > > >             > >             > > to
    > > >             > >             > >     > serialize
    > > >             > >             > >     >         their own headers, and it
    > > > would be more
    > > >             > > ideal if we can
    > > >             > >             > avoid
    > > >             > >             > >     > leaking
    > > >             > >             > >     >         third-party headers into
    > > > applications. This
    > > >             > > is difficult to
    > > >             > >             > > do
    > > >             > >             > >     > with the
    > > >             > >             > >     >         current interceptors
    > > because
    > > > they share the
    > > >             > > record objects
    > > >             > >             > > with
    > > >             > >             > >     > the common
    > > >             > >             > >     >         API. What I had in mind
    > is
    > > > something like
    > > >             > an
    > > >             > > extension of
    > > >             > >             > the
    > > >             > >             > >     > current
    > > >             > >             > >     >         interceptors which
    > exposed
    > > a
    > > > different
    > > >             > > object (e.g.
    > > >             > >             > >     > `RecordAndHeaders`).
    > > >             > >             > >     >         The challenge is for
    > > MM-like
    > > > use cases. Let
    > > >             > > me see if I can
    > > >             > >             > > come
    > > >             > >             > >     > up with a
    > > >             > >             > >     >         concrete proposal for
    > that
    > > > problem.
    > > >             > >             > >     >
    > > >             > >             > >     >         -Jason
    > > >             > >             > >     >
    > > >             > >             > >     >
    > > >             > >             > >     >
    > > >             > >             > >     >         On Fri, Feb 17, 2017 at
    > > > 11:55 AM, Michael
    > > >             > > Pearce <
    > > >             > >             > >     > Michael.Pearce@ig.com>
    > > >             > >             > >     >         wrote:
    > > >             > >             > >     >
    > > >             > >             > >     >         > I am happy to move the
    > > > definition of the
    > > >             > > header into the
    > > >             > >             > > message
    > > >             > >             > >     > body, but
    > > >             > >             > >     >         > would cause us not to
    > > lazy
    > > >             > > initialise/parse the headers,
    > > >             > >             > as
    > > >             > >             > >     > obviously, we
    > > >             > >             > >     >         > would have to traverse
    > > > these reading the
    > > >             > > message.
    > > >             > >             > >     >         >
    > > >             > >             > >     >         > This was actually one
    > of
    > > > Jay’s requests:
    > > >             > >             > >     >         >
    > > >             > >             > >     >         > “    2. I think we
    > should
    > > > think about
    > > >             > > creating the Map
    > > >             > >             > > lazily to
    > > >             > >             > >     > avoid
    > > >             > >             > >     >         >     parsing out all the
    > > > headers into
    > > >             > > little objects.
    > > >             > >             > > HashMaps
    > > >             > >             > >     > themselves
    > > >             > >             > >     >         > are
    > > >             > >             > >     >         >     kind of expensive
    > and
    > > > the consumer is
    > > >             > > very perf
    > > >             > >             > > sensitive so
    > > >             > >             > >     > and making
    > > >             > >             > >     >         >     gazillions of
    > > hashmaps
    > > > that may or
    > > >             > may
    > > >             > > not get used
    > > >             > >             > is
    > > >             > >             > >     > probably a bad
    > > >             > >             > >     >         > idea.”
    > > >             > >             > >     >         >
    > > >             > >             > >     >         >
    > > >             > >             > >     >         >
    > > >             > >             > >     >         >
    > > >             > >             > >     >         >
    > > >             > >             > >     >         > On 17/02/2017, 19:44,
    > > > "Michael Pearce" <
    > > >             > >             > > Michael.Pearce@ig.com>
    > > >             > >             > >     > wrote:
    > > >             > >             > >     >         >
    > > >             > >             > >     >         >     Yes exactly we have
    > > > access to the
    > > >             > > records thus why
    > > >             > >             > the
    > > >             > >             > >     > header should
    > > >             > >             > >     >         > be accessible via it
    > and
    > > > not hidden for
    > > >             > > only interceptors
    > > >             > >             > > to
    > > >             > >             > >     > access.
    > > >             > >             > >     >         >
    > > >             > >             > >     >         >     Sent using OWA for
    > > > iPhone
    > > >             > >             > >     >         >
    > > >  ______________________________
    > > >             > > __________
    > > >             > >             > >     >         >     From: Magnus
    > > Edenhill <
    > > >             > > magnus@edenhill.se>
    > > >             > >             > >     >         >     Sent: Friday,
    > > February
    > > > 17, 2017
    > > >             > > 7:34:49 PM
    > > >             > >             > >     >         >     To:
    > > > dev@kafka.apache.org
    > > >             > >             > >     >         >     Subject: Re:
    > > [DISCUSS]
    > > > KIP-82 - Add
    > > >             > > Record Headers
    > > >             > >             > >     >         >
    > > >             > >             > >     >         >     Big +1 on VarInts.
    > > >             > >             > >     >         >     CPUs are fast,
    > memory
    > > > is slow.
    > > >             > >             > >     >         >
    > > >             > >             > >     >         >     I agree with Jason
    > > > that we'll want to
    > > >             > > continue
    > > >             > >             > > verifying
    > > >             > >             > >     > messages,
    > > >             > >             > >     >         >     including their
    > > > headers, so while I
    > > >             > > appreciate the
    > > >             > >             > > idea of
    > > >             > >             > >     > the opaque
    > > >             > >             > >     >         >     header blob it
    > won't
    > > > be useful in
    > > >             > > practice.
    > > >             > >             > >     >         >
    > > >             > >             > >     >         >     /Magnus
    > > >             > >             > >     >         >
    > > >             > >             > >     >         >     2017-02-17 10:41
    > > > GMT-08:00 Jason
    > > >             > > Gustafson <
    > > >             > >             > >     > jason@confluent.io>:
    > > >             > >             > >     >         >
    > > >             > >             > >     >         >     > Sorry, my
    > mistake.
    > > > The consumer
    > > >             > > interceptor is per
    > > >             > >             > > batch,
    > > >             > >             > >     > though I'm
    > > >             > >             > >     >         > not
    > > >             > >             > >     >         >     > sure that's an
    > > > actual limitation
    > > >             > > since you still
    > > >             > >             > have
    > > >             > >             > >     > access to the
    > > >             > >             > >     >         >     > individual
    > records.
    > > >             > >             > >     >         >     >
    > > >             > >             > >     >         >     > -Jason
    > > >             > >             > >     >         >     >
    > > >             > >             > >     >         >     > On Fri, Feb 17,
    > > 2017
    > > > at 10:39 AM,
    > > >             > > Jason Gustafson <
    > > >             > >             > >     >         > jason@confluent.io>
    > > >             > >             > >     >         >     > wrote:
    > > >             > >             > >     >         >     >
    > > >             > >             > >     >         >     > > Re headers as
    > > byte
    > > > array and
    > > >             > > future use by
    > > >             > >             > broker.
    > > >             > >             > > This
    > > >             > >             > >     > doesn't
    > > >             > >             > >     >         > take away
    > > >             > >             > >     >         >     > >> from that at
    > > all.
    > > > Nor makes it
    > > >             > > difficult at all
    > > >             > >             > > in my
    > > >             > >             > >     > opinion.
    > > >             > >             > >     >         >     > >
    > > >             > >             > >     >         >     > >
    > > >             > >             > >     >         >     > > Yeah, I didn't
    > > say
    > > > it was
    > > >             > > difficult, only
    > > >             > >             > awkward.
    > > >             > >             > > You
    > > >             > >             > >     > wouldn't
    > > >             > >             > >     >         > write the
    > > >             > >             > >     >         >     > > schema that way
    > > if
    > > > you were
    > > >             > > planning to use it on
    > > >             > >             > > the
    > > >             > >             > >     > brokers from
    > > >             > >             > >     >         > the
    > > >             > >             > >     >         >     > > beginning. Note
    > > > also that one of
    > > >             > > the benefits of
    > > >             > >             > > letting
    > > >             > >             > >     > the broker
    > > >             > >             > >     >         >     > > understand
    > > headers
    > > > is that it can
    > > >             > > validate that
    > > >             > >             > > they are
    > > >             > >             > >     > properly
    > > >             > >             > >     >         >     > > formatted. If
    > > cost
    > > > is the only
    > > >             > > concern, we should
    > > >             > >             > >     > confirm its
    > > >             > >             > >     >         > impact
    > > >             > >             > >     >         >     > > through
    > > > performance testing.
    > > >             > >             > >     >         >     > >
    > > >             > >             > >     >         >     > > One of the key
    > > use
    > > > cases requires
    > > >             > > access on
    > > >             > >             > > consume at
    > > >             > >             > >     > per
    > > >             > >             > >     >         > event/message
    > > >             > >             > >     >         >     > >> level at the
    > > > point that message
    > > >             > > is being
    > > >             > >             > > processed, as
    > > >             > >             > >     > such the
    > > >             > >             > >     >         > batch
    > > >             > >             > >     >         >     > >> interceptors
    > and
    > > > batch consume
    > > >             > > api isn't
    > > >             > >             > > suitable. It
    > > >             > >             > >     > needs to be
    > > >             > >             > >     >         > at the
    > > >             > >             > >     >         >     > >> record level.
    > > >             > >             > >     >         >     > >
    > > >             > >             > >     >         >     > >
    > > >             > >             > >     >         >     > > I'm not sure I
    > > > understand the
    > > >             > > point about
    > > >             > >             > batching.
    > > >             > >             > >     > Interceptors
    > > >             > >             > >     >         > are
    > > >             > >             > >     >         >     > > applied
    > > > per-message, right?
    > > >             > >             > >     >         >     > >
    > > >             > >             > >     >         >     > > My intent on
    > > > interceptors is to
    > > >             > > keep the usage of
    > > >             > >             > > headers
    > > >             > >             > >     >         > well-defined so
    > > >             > >             > >     >         >     > > that they don't
    > > > start leaking
    > > >             > > unnecessarily into
    > > >             > >             > >     > applications. My
    > > >             > >             > >     >         > guess
    > > >             > >             > >     >         >     > is
    > > >             > >             > >     >         >     > > that it's
    > > probably
    > > > inevitable,
    > > >             > but
    > > >             > > isolating it
    > > >             > >             > in
    > > >             > >             > > the
    > > >             > >             > >     >         > interceptors would
    > > >             > >             > >     >         >     > > at least give
    > > > people a second
    > > >             > > thought before
    > > >             > >             > > deciding to
    > > >             > >             > >     > use it.
    > > >             > >             > >     >         > The main
    > > >             > >             > >     >         >     > > challenge in my
    > > > mind is figuring
    > > >             > > out how an MM
    > > >             > >             > use
    > > >             > >             > > case
    > > >             > >             > >     > would
    > > >             > >             > >     >         > work. It
    > > >             > >             > >     >         >     > > would be more
    > > > cumbersome to
    > > >             > > replicate headers
    > > >             > >             > > through an
    > > >             > >             > >     >         > interceptor,
    > > >             > >             > >     >         >     > > though arguably
    > > MM
    > > > should be
    > > >             > > working at a lower
    > > >             > >             > > level
    > > >             > >             > >     > anyway.
    > > >             > >             > >     >         >     > >
    > > >             > >             > >     >         >     > > -Jason
    > > >             > >             > >     >         >     > >
    > > >             > >             > >     >         >     > > On Fri, Feb 17,
    > > > 2017 at 10:16 AM,
    > > >             > > Michael Pearce
    > > >             > >             > <
    > > >             > >             > >     >         > Michael.Pearce@ig.com>
    > > >             > >             > >     >         >     > > wrote:
    > > >             > >             > >     >         >     > >
    > > >             > >             > >     >         >     > >> Re headers
    > > > available on the
    > > >             > > record  va
    > > >             > >             > > interceptors only
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >> One of the key
    > > > use cases
    > > >             > requires
    > > >             > > access on
    > > >             > >             > > consume at
    > > >             > >             > >     > per
    > > >             > >             > >     >         > event/message
    > > >             > >             > >     >         >     > >> level at the
    > > > point that message
    > > >             > > is being
    > > >             > >             > > processed, as
    > > >             > >             > >     > such the
    > > >             > >             > >     >         > batch
    > > >             > >             > >     >         >     > >> interceptors
    > and
    > > > batch consume
    > > >             > > api isn't
    > > >             > >             > > suitable. It
    > > >             > >             > >     > needs to be
    > > >             > >             > >     >         > at the
    > > >             > >             > >     >         >     > >> record level.
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >> This anyhow is
    > > > similar to
    > > >             > > jms/http/amqp where
    > > >             > >             > > headers
    > > >             > >             > >     > are
    > > >             > >             > >     >         > available to
    > > >             > >             > >     >         >     > >> consuming
    > > > applications.
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >> Re headers as
    > > > byte array and
    > > >             > > future use by
    > > >             > >             > > broker. This
    > > >             > >             > >     > doesn't
    > > >             > >             > >     >         > take
    > > >             > >             > >     >         >     > away
    > > >             > >             > >     >         >     > >> from that at
    > > all.
    > > > Nor makes it
    > > >             > > difficult at all
    > > >             > >             > > in my
    > > >             > >             > >     > opinion.
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >> Sent using OWA
    > > > for iPhone
    > > >             > >             > >     >         >     > >>
    > > > ______________________________
    > > >             > > __________
    > > >             > >             > >     >         >     > >> From: Jason
    > > > Gustafson <
    > > >             > > jason@confluent.io>
    > > >             > >             > >     >         >     > >> Sent: Friday,
    > > > February 17, 2017
    > > >             > > 5:55:42 PM
    > > >             > >             > >     >         >     > >> To:
    > > > dev@kafka.apache.org
    > > >             > >             > >     >         >     > >> Subject: Re:
    > > > [DISCUSS] KIP-82 -
    > > >             > > Add Record
    > > >             > >             > Headers
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> > Would you be
    > > > proposing in
    > > >             > > KIP-98 to convert
    > > >             > >             > the
    > > >             > >             > > other
    > > >             > >             > >     > message
    > > >             > >             > >     >         > int’s
    > > >             > >             > >     >         >     > (key
    > > >             > >             > >     >         >     > >> > length,
    > value
    > > > length) also to
    > > >             > > varint to keep
    > > >             > >             > it
    > > >             > >             > >     > uniform.
    > > >             > >             > >     >         >     > >> > Also I
    > assume
    > > > there will be a
    > > >             > > static or helper
    > > >             > >             > > method
    > > >             > >             > >     > made to
    > > >             > >             > >     >         >     > write/read
    > > >             > >             > >     >         >     > >> > these in the
    > > > client and
    > > >             > server.
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >> Yes, that is
    > > what
    > > > we are
    > > >             > > proposing, so using
    > > >             > >             > > varints
    > > >             > >             > >     > for headers
    > > >             > >             > >     >         > would
    > > >             > >             > >     >         >     > be
    > > >             > >             > >     >         >     > >> consistent
    > with
    > > > the rest of the
    > > >             > > message. We have
    > > >             > >             > > used
    > > >             > >             > >     > static
    > > >             > >             > >     >         > helper
    > > >             > >             > >     >         >     > >> methods
    > > >             > >             > >     >         >     > >> in our
    > prototype
    > > > implementation.
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >> The cost of
    > > > parsing, we want to
    > > >             > > parse/interpret
    > > >             > >             > > the
    > > >             > >             > >     > headers
    > > >             > >             > >     >         > lazily (this
    > > >             > >             > >     >         >     > >> is
    > > >             > >             > >     >         >     > >> > a key point
    > > > brought up earlier
    > > >             > > in discussions)
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >> I'm a bit
    > > > skeptical of this. Has
    > > >             > > anyone done the
    > > >             > >             > >     > performance
    > > >             > >             > >     >         > testing? I
    > > >             > >             > >     >         >     > >> can
    > > >             > >             > >     >         >     > >> probably
    > > > implement it and test
    > > >             > it
    > > >             > > if no one else
    > > >             > >             > > has. I
    > > >             > >             > >     > was also
    > > >             > >             > >     >         > under
    > > >             > >             > >     >         >     > the
    > > >             > >             > >     >         >     > >> impression
    > that
    > > > there may be use
    > > >             > > cases down the
    > > >             > >             > > road
    > > >             > >             > >     > where the
    > > >             > >             > >     >         > broker
    > > >             > >             > >     >         >     > >> would
    > > >             > >             > >     >         >     > >> need to
    > > interpret
    > > > headers. That
    > > >             > > wouldn't be off
    > > >             > >             > > the
    > > >             > >             > >     > table in the
    > > >             > >             > >     >         > future
    > > >             > >             > >     >         >     > if
    > > >             > >             > >     >         >     > >> it's
    > represented
    > > > as bytes, but
    > > >             > it
    > > >             > > would be quite
    > > >             > >             > > a bit
    > > >             > >             > >     > more
    > > >             > >             > >     >         > awkward,
    > > >             > >             > >     >         >     > >> right?
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >> By the way,
    > one
    > > > question I have
    > > >             > > been wondering
    > > >             > >             > > about. My
    > > >             > >             > >     >         > understanding
    > > >             > >             > >     >         >     > is
    > > >             > >             > >     >         >     > >> that headers
    > are
    > > > primarily for
    > > >             > > use cases where a
    > > >             > >             > >     > third-party
    > > >             > >             > >     >         > components
    > > >             > >             > >     >         >     > >> wants to
    > enrich
    > > > messages without
    > > >             > > needing to
    > > >             > >             > > understand
    > > >             > >             > >     > or modify
    > > >             > >             > >     >         > the
    > > >             > >             > >     >         >     > >> schema
    > > >             > >             > >     >         >     > >> of the message
    > > > key and value.
    > > >             > For
    > > >             > > the
    > > >             > >             > applications
    > > >             > >             > >     > which directly
    > > >             > >             > >     >         >     > produce
    > > >             > >             > >     >         >     > >> and consume
    > the
    > > > messages and
    > > >             > > control the
    > > >             > >             > key/value
    > > >             > >             > >     > schema
    > > >             > >             > >     >         > directly, it
    > > >             > >             > >     >         >     > >> seems we would
    > > > rather have them
    > > >             > > implement
    > > >             > >             > headers
    > > >             > >             > >     > directly in
    > > >             > >             > >     >         > their own
    > > >             > >             > >     >         >     > >> schema.
    > > Supposing
    > > > for the sake
    > > >             > of
    > > >             > > argument that
    > > >             > >             > > it was
    > > >             > >             > >     > possible,
    > > >             > >             > >     >         > my
    > > >             > >             > >     >         >     > >> question is
    > > > whether it be
    > > >             > > sufficient to expose
    > > >             > >             > the
    > > >             > >             > >     > headers in the
    > > >             > >             > >     >         >     > >> interceptor
    > API
    > > > and not in the
    > > >             > > common API?
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >> -Jason
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >> On Fri, Feb
    > 17,
    > > > 2017 at 3:26 AM,
    > > >             > > Michael Pearce
    > > >             > >             > <
    > > >             > >             > >     >         > Michael.Pearce@ig.com>
    > > >             > >             > >     >         >     > >> wrote:
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >> > On the point
    > > of
    > > > varInts
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> > Would you be
    > > > proposing in
    > > >             > > KIP-98 to convert
    > > >             > >             > the
    > > >             > >             > > other
    > > >             > >             > >     > message
    > > >             > >             > >     >         > int’s
    > > >             > >             > >     >         >     > (key
    > > >             > >             > >     >         >     > >> > length,
    > value
    > > > length) also to
    > > >             > > varint to keep
    > > >             > >             > it
    > > >             > >             > >     > uniform.
    > > >             > >             > >     >         >     > >> > Also I
    > assume
    > > > there will be a
    > > >             > > static or helper
    > > >             > >             > > method
    > > >             > >             > >     > made to
    > > >             > >             > >     >         >     > write/read
    > > >             > >             > >     >         >     > >> > these in the
    > > > client and
    > > >             > server.
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> > Cheers
    > > >             > >             > >     >         >     > >> > Mike
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> > On
    > 17/02/2017,
    > > > 11:22, "Michael
    > > >             > > Pearce" <
    > > >             > >             > >     > Michael.Pearce@ig.com>
    > > >             > >             > >     >         > wrote:
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> >     On the
    > > > point re: headers
    > > >             > in
    > > >             > > the message
    > > >             > >             > > protocol
    > > >             > >             > >     > being a
    > > >             > >             > >     >         > byte
    > > >             > >             > >     >         >     > array
    > > >             > >             > >     >         >     > >> > and not a
    > > count
    > > > of elements
    > > >             > > followed by the
    > > >             > >             > > elements.
    > > >             > >             > >     > Again
    > > >             > >             > >     >         > this was
    > > >             > >             > >     >         >     > >> >
    > > > discussed/argued previously.
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> >     It was
    > > > agreed on for a few
    > > >             > > reasons some of
    > > >             > >             > > which
    > > >             > >             > >     > you have
    > > >             > >             > >     >         >     > obviously
    > > >             > >             > >     >         >     > >> > picked up
    > on:
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> >     Broker
    > is
    > > > able to pass it
    > > >             > > through opaquely
    > > >             > >             > >     >         >     > >> >     The cost
    > > of
    > > > parsing, we
    > > >             > > want to
    > > >             > >             > > parse/interpret
    > > >             > >             > >     > the headers
    > > >             > >             > >     >         > lazily
    > > >             > >             > >     >         >     > >> > (this is a
    > key
    > > > point brought
    > > >             > up
    > > >             > > earlier in
    > > >             > >             > >     > discussions)
    > > >             > >             > >     >         >     > >> >     Headers
    > > can
    > > > be copied from
    > > >             > > consumer record
    > > >             > >             > > to
    > > >             > >             > >     > producer
    > > >             > >             > >     >         > record (aka
    > > >             > >             > >     >         >     > >> > mirror
    > makers
    > > > etc) without
    > > >             > > parsing if no
    > > >             > >             > > changes are
    > > >             > >             > >     > being made
    > > >             > >             > >     >         > or
    > > >             > >             > >     >         >     > being
    > > >             > >             > >     >         >     > >> > looked at.
    > > >             > >             > >     >         >     > >> >     Keeps
    > the
    > > > broker agnostic
    > > >             > > to the format
    > > >             > >             > >     >         >     > >> >     You need
    > > an
    > > > int32 either
    > > >             > > for the byte size
    > > >             > >             > > of the
    > > >             > >             > >     > headers,
    > > >             > >             > >     >         > or for
    > > >             > >             > >     >         >     > >> the
    > > >             > >             > >     >         >     > >> > count of
    > > > elements, so
    > > >             > overheads
    > > >             > > are the same,
    > > >             > >             > > but
    > > >             > >             > >     > with going
    > > >             > >             > >     >         > with an
    > > >             > >             > >     >         >     > >> opaque
    > > >             > >             > >     >         >     > >> > byte array
    > has
    > > > the above
    > > >             > > advantages.
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> >     Cheers
    > > >             > >             > >     >         >     > >> >     Mike
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> >     On
    > > > 17/02/2017, 02:50,
    > > >             > > "Jason Gustafson" <
    > > >             > >             > >     > jason@confluent.io
    > > >             > >             > >     >         > >
    > > >             > >             > >     >         >     > wrote:
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> >
    >  Sorry,
    > > > should have
    > > >             > > noted that the
    > > >             > >             > > performance
    > > >             > >             > >     > testing
    > > >             > >             > >     >         > was done
    > > >             > >             > >     >         >     > >> > using the
    > > >             > >             > >     >         >     > >> >
    > > >  producer performance
    > > >             > > tool shipped with
    > > >             > >             > > Kafka.
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> >
    >  -Jason
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> >         On
    > > Thu,
    > > > Feb 16, 2017
    > > >             > at
    > > >             > > 6:44 PM, Jason
    > > >             > >             > >     > Gustafson <
    > > >             > >             > >     >         >     > >> >
    > > > jason@confluent.io> wrote:
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> >         >
    > Hey
    > > > Nacho,
    > > >             > >             > >     >         >     > >> >         >
    > > >             > >             > >     >         >     > >> >         >
    > I've
    > > > compared
    > > >             > > performance of our
    > > >             > >             > > KIP-98
    > > >             > >             > >     >         > implementation with
    > > >             > >             > >     >         >     > >> and
    > > >             > >             > >     >         >     > >> > without
    > > >             > >             > >     >         >     > >> >         >
    > > > varints. For
    > > >             > messages
    > > >             > > around 128
    > > >             > >             > > bytes, we
    > > >             > >             > >     > see an
    > > >             > >             > >     >         > increase
    > > >             > >             > >     >         >     > in
    > > >             > >             > >     >         >     > >> > throughput
    > of
    > > >             > >             > >     >         >     > >> >         >
    > > about
    > > > 30% using the
    > > >             > > default
    > > >             > >             > > configuration
    > > >             > >             > >     > settings.
    > > >             > >             > >     >         > At 256
    > > >             > >             > >     >         >     > >> > bytes, the
    > > >             > >             > >     >         >     > >> >         >
    > > > increase is around
    > > >             > > 16%. Obviously
    > > >             > >             > the
    > > >             > >             > >     > performance
    > > >             > >             > >     >         > converge
    > > >             > >             > >     >         >     > as
    > > >             > >             > >     >         >     > >> > messages get
    > > >             > >             > >     >         >     > >> >         >
    > > > larger, but it seems
    > > >             > > well worth the
    > > >             > >             > > cost.
    > > >             > >             > >     > Note that
    > > >             > >             > >     >         > we are
    > > >             > >             > >     >         >     > >> also
    > > >             > >             > >     >         >     > >> > seeing a
    > > >             > >             > >     >         >     > >> >         >
    > > > substantial
    > > >             > > performance increase
    > > >             > >             > > against
    > > >             > >             > >     > trunk
    > > >             > >             > >     >         > primarily
    > > >             > >             > >     >         >     > >> because
    > > >             > >             > >     >         >     > >> > of the
    > > >             > >             > >     >         >     > >> >         >
    > much
    > > > more efficient
    > > >             > > packing that
    > > >             > >             > > varints
    > > >             > >             > >     > provide us.
    > > >             > >             > >     >         >     > Anything
    > > >             > >             > >     >         >     > >> > adding to
    > > >             > >             > >     >         >     > >> >         >
    > > > message overhead,
    > > >             > > such as record
    > > >             > >             > > headers,
    > > >             > >             > >     > would only
    > > >             > >             > >     >         >     > increase
    > > >             > >             > >     >         >     > >> > the relative
    > > >             > >             > >     >         >     > >> >         >
    > > > difference. (Of
    > > >             > > course take these
    > > >             > >             > > numbers
    > > >             > >             > >     > with a
    > > >             > >             > >     >         > grain of
    > > >             > >             > >     >         >     > salt
    > > >             > >             > >     >         >     > >> > since I have
    > > >             > >             > >     >         >     > >> >         >
    > only
    > > > used the
    > > >             > default
    > > >             > > settings with
    > > >             > >             > > both
    > > >             > >             > >     > the producer
    > > >             > >             > >     >         > and
    > > >             > >             > >     >         >     > >> broker
    > > >             > >             > >     >         >     > >> > on my
    > > >             > >             > >     >         >     > >> >         >
    > > local
    > > > machine. We
    > > >             > > intend to provide
    > > >             > >             > > more
    > > >             > >             > >     > extensive
    > > >             > >             > >     >         >     > performance
    > > >             > >             > >     >         >     > >> > details as
    > > >             > >             > >     >         >     > >> >         >
    > part
    > > > of the work for
    > > >             > > KIP-98.)
    > > >             > >             > >     >         >     > >> >         >
    > > >             > >             > >     >         >     > >> >         >
    > The
    > > > implementation
    > > >             > we
    > > >             > > are using is
    > > >             > >             > > from
    > > >             > >             > >     > protobuf (
    > > >             > >             > >     >         >     > >> >         >
    > > >             > > https://developers.google.com/
    > > >             > >             > >     >         >     >
    > > > protocol-buffers/docs/encoding
    > > >             > >             > >     >         >     > >> ),
    > > >             > >             > >     >         >     > >> > which is
    > > >             > >             > >     >         >     > >> >         >
    > also
    > > > used in HBase.
    > > >             > > It is trivial to
    > > >             > >             > >     > implement and as
    > > >             > >             > >     >         > far
    > > >             > >             > >     >         >     > as I
    > > >             > >             > >     >         >     > >> > know doesn't
    > > >             > >             > >     >         >     > >> >         >
    > > > suffer from the
    > > >             > > aliasing problem you
    > > >             > >             > > are
    > > >             > >             > >     > describing. I
    > > >             > >             > >     >         >     > checked
    > > >             > >             > >     >         >     > >> > with Magnus
    > > >             > >             > >     >         >     > >> >         >
    > (the
    > > > author of
    > > >             > > librdkafka) and he
    > > >             > >             > > agreed
    > > >             > >             > >     > that the
    > > >             > >             > >     >         > savings
    > > >             > >             > >     >         >     > >> seemed
    > > >             > >             > >     >         >     > >> > worth the
    > > >             > >             > >     >         >     > >> >         >
    > cost
    > > > of
    > > >             > > implementation.
    > > >             > >             > >     >         >     > >> >         >
    > > >             > >             > >     >         >     > >> >         >
    > > -Jason
    > > >             > >             > >     >         >     > >> >         >
    > > >             > >             > >     >         >     > >> >         > On
    > > > Thu, Feb 16, 2017
    > > >             > > at 4:32 PM,
    > > >             > >             > > Ignacio
    > > >             > >             > >     > Solis <
    > > >             > >             > >     >         >     > >>
    > isolis@igso.net
    > > >
    > > >             > >             > >     >         >     > >> > wrote:
    > > >             > >             > >     >         >     > >> >         >
    > > >             > >             > >     >         >     > >> >         >>
    > > > -VarInts
    > > >             > >             > >     >         >     > >> >         >>
    > > >             > >             > >     >         >     > >> >         >>
    > I'm
    > > > one of the
    > > >             > > people (if not the
    > > >             > >             > > most)
    > > >             > >             > >     > opposed to
    > > >             > >             > >     >         > VarInts.
    > > >             > >             > >     >         >     > >> > VarInts
    > > >             > >             > >     >         >     > >> >         >>
    > > have
    > > > a place, but
    > > >             > > this is not it.
    > > >             > >             > >  (We
    > > >             > >             > >     > had a large
    > > >             > >             > >     >         >     > >> discussion
    > > >             > >             > >     >         >     > >> > about
    > > >             > >             > >     >         >     > >> >         >>
    > > them
    > > > at the
    > > >             > > beginning of KIP-82
    > > >             > >             > time)
    > > >             > >             > >     >         >     > >> >         >>
    > > >             > >             > >     >         >     > >> >         >>
    > If
    > > > anybody has real
    > > >             > > life
    > > >             > >             > performance
    > > >             > >             > >     > numbers of
    > > >             > >             > >     >         > VarInts
    > > >             > >             > >     >         >     > >> > improving
    > > >             > >             > >     >         >     > >> >         >>
    > > > things or
    > > >             > > significantly reducing
    > > >             > >             > > resources
    > > >             > >             > >     > I would
    > > >             > >             > >     >         > like to
    > > >             > >             > >     >         >     > >> know
    > > >             > >             > >     >         >     > >> > what
    > > >             > >             > >     >         >     > >> >         >>
    > > that
    > > > case may be.
    > > >             > > Yes, you can save
    > > >             > >             > > some
    > > >             > >             > >     > bytes here
    > > >             > >             > >     >         > and
    > > >             > >             > >     >         >     > >> there,
    > > >             > >             > >     >         >     > >> > but
    > > >             > >             > >     >         >     > >> >         >>
    > > this
    > > > is probably
    > > >             > > insignificant to
    > > >             > >             > the
    > > >             > >             > >     > overall system
    > > >             > >             > >     >         >     > behavior
    > > >             > >             > >     >         >     > >> > and
    > > >             > >             > >     >         >     > >> >         >>
    > > > storage
    > > >             > > requirements.  -- I say
    > > >             > >             > this
    > > >             > >             > > with
    > > >             > >             > >     > respect to
    > > >             > >             > >     >         > using
    > > >             > >             > >     >         >     > >> > VarInts in
    > > >             > >             > >     >         >     > >> >         >>
    > the
    > > > protocol
    > > >             > itself,
    > > >             > > not as part of
    > > >             > >             > > the
    > > >             > >             > >     > data.
    > > >             > >             > >     >         >     > >> >         >>
    > > >             > >             > >     >         >     > >> >         >>
    > > > VarInts require you
    > > >             > > to parse the
    > > >             > >             > Int
    > > >             > >             > >     > before using it
    > > >             > >             > >     >         > and
    > > >             > >             > >     >         >     > >> > depending on
    > > >             > >             > >     >         >     > >> >         >>
    > the
    > > > encoding they
    > > >             > > can suffer from
    > > >             > >             > > aliasing
    > > >             > >             > >     > (multiple
    > > >             > >             > >     >         >     > >> >
    > > representations
    > > >             > >             > >     >         >     > >> >         >>
    > for
    > > > the same
    > > >             > value).
    > > >             > >             > >     >         >     > >> >         >>
    > > >             > >             > >     >         >     > >> >         >>
    > Why
    > > > add complexity?
    > > >             > >             > >     >         >     > >> >         >>
    > > >             > >             > >     >         >     > >> >         >>
    > > Nacho
    > > >             > >             > >     >         >     > >> >         >>
    > > >             > >             > >     >         >     > >> >         >>
    > > >             > >             > >     >         >     > >> >         >>
    > On
    > > > Thu, Feb 16,
    > > >             > 2017
    > > >             > > at 10:29 AM,
    > > >             > >             > > Colin
    > > >             > >             > >     > McCabe <
    > > >             > >             > >     >         >     > >> >
    > > > cmccabe@apache.org>
    > > >             > >             > >     >         >     > >> >         >>
    > > > wrote:
    > > >             > >             > >     >         >     > >> >         >> >
    > > +1
    > > > for varints
    > > >             > > here-- it would
    > > >             > >             > save
    > > >             > >             > >     > quite a bit of
    > > >             > >             > >     >         > space.
    > > >             > >             > >     >         >     > >> > They are
    > > >             > >             > >     >         >     > >> >         >> >
    > > > pretty quick to
    > > >             > > implement as
    > > >             > >             > well.
    > > >             > >             > >     >         >     > >> >         >> >
    > > >             > >             > >     >         >     > >> >         >>
    > > I
    > > > think it makes
    > > >             > > sense for values
    > > >             > >             > > to be
    > > >             > >             > >     > byte
    > > >             > >             > >     >         > arrays.
    > > >             > >             > >     >         >     > Users
    > > >             > >             > >     >         >     > >> > might want
    > > >             > >             > >     >         >     > >> >         >> >
    > > to
    > > > attach
    > > >             > > arbitrary payloads;
    > > >             > >             > they
    > > >             > >             > >     > shouldn't be
    > > >             > >             > >     >         > forced to
    > > >             > >             > >     >         >     > >> > serialize
    > > >             > >             > >     >         >     > >> >         >> >
    > > > everything to
    > > >             > Java
    > > >             > > strings.
    > > >             > >             > >     >         >     > >> >         >> >
    > > >             > >             > >     >         >     > >> >         >> >
    > > > best,
    > > >             > >             > >     >         >     > >> >         >> >
    > > > Colin
    > > >             > >             > >     >         >     > >> >         >> >
    > > >             > >             > >     >         >     > >> >         >> >
    > > >             > >             > >     >         >     > >> >         >> >
    > > On
    > > > Thu, Feb 16,
    > > >             > > 2017, at 09:52,
    > > >             > >             > > Jason
    > > >             > >             > >     > Gustafson
    > > >             > >             > >     >         > wrote:
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > Hey Michael,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > Hmm, I guess the
    > > >             > > point of
    > > >             > >             > > representing
    > > >             > >             > >     > it as
    > > >             > >             > >     >         > bytes is to
    > > >             > >             > >     >         >     > >> > allow the
    > > >             > >             > >     >         >     > >> >         >>
    > > > broker
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > to pass it
    > > >             > > through opaquely? Is
    > > >             > >             > > the
    > > >             > >             > >     > cost of
    > > >             > >             > >     >         > parsing
    > > >             > >             > >     >         >     > them a
    > > >             > >             > >     >         >     > >> > concern, or
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > are
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > we simply trying
    > > >             > > to ensure that
    > > >             > >             > > the
    > > >             > >             > >     > broker stays
    > > >             > >             > >     >         >     > agnostic
    > > >             > >             > >     >         >     > >> to
    > > >             > >             > >     >         >     > >> > the
    > > >             > >             > >     >         >     > >> >         >>
    > > > format?
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > On varints, I
    > > >             > > think adding
    > > >             > >             > > support for
    > > >             > >             > >     > them makes
    > > >             > >             > >     >         > less
    > > >             > >             > >     >         >     > >> sense
    > > >             > >             > >     >         >     > >> > for an
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > isolated use
    > > >             > > case, but as part
    > > >             > >             > of
    > > >             > >             > > a
    > > >             > >             > >     > more holistic
    > > >             > >             > >     >         > change
    > > >             > >             > >     >         >     > >> > (such as
    > what
    > > >             > >             > >     >         >     > >> >         >>
    > we
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > have proposed in
    > > >             > > KIP-98), I
    > > >             > >             > think
    > > >             > >             > > they
    > > >             > >             > >     > are
    > > >             > >             > >     >         > justifiable.
    > > >             > >             > >     >         >     > If
    > > >             > >             > >     >         >     > >> > we add them,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > then the need to
    > > >             > > use attributes
    > > >             > >             > > becomes
    > > >             > >             > >     > quite a
    > > >             > >             > >     >         > bit
    > > >             > >             > >     >         >     > >> weaker,
    > > >             > >             > >     >         >     > >> > right? The
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > other thing I
    > > >             > > find slightly odd
    > > >             > >             > > is the
    > > >             > >             > >     > fact that
    > > >             > >             > >     >         > null
    > > >             > >             > >     >         >     > >> > headers has
    > no
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > actual
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > semantic meaning
    > > >             > > for the message
    > > >             > >             > >     > (unlike null
    > > >             > >             > >     >         > keys and
    > > >             > >             > >     >         >     > >> > values). It
    > is
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > just
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > a
    > > > space
    > > >             > > optimization. It seems a
    > > >             > >             > > bit
    > > >             > >             > >     > better to
    > > >             > >             > >     >         > always
    > > >             > >             > >     >         >     > use
    > > >             > >             > >     >         >     > >> > size 0 to
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > indicate having
    > > >             > > no headers.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > Overall, the
    > > >             > main
    > > >             > > point is
    > > >             > >             > > ensuring
    > > >             > >             > >     > that the
    > > >             > >             > >     >         > message
    > > >             > >             > >     >         >     > >> schema
    > > >             > >             > >     >         >     > >> > remains
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > consistent,
    > > >             > > either within the
    > > >             > >             > > larger
    > > >             > >             > >     > protocol, or
    > > >             > >             > >     >         > at a
    > > >             > >             > >     >         >     > >> > minimum
    > within
    > > >             > >             > >     >         >     > >> >         >>
    > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > message itself.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > -Jason
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > On Thu, Feb 16,
    > > >             > > 2017 at 6:39 AM,
    > > >             > >             > >     > Michael Pearce <
    > > >             > >             > >     >         >     > >> >
    > > > Michael.Pearce@ig.com
    > > >             > >             > >     >         >     > >> >         >> >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > wrote:
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > Hi Jason,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > On point 1) in
    > > >             > > the message
    > > >             > >             > > protocol
    > > >             > >             > >     > the headers
    > > >             > >             > >     >         > are
    > > >             > >             > >     >         >     > >> simply
    > > >             > >             > >     >         >     > >> > a byte
    > > >             > >             > >     >         >     > >> >         >>
    > > > array,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > as like the
    > > >             > key
    > > >             > > or value, this
    > > >             > >             > > is to
    > > >             > >             > >     > clearly
    > > >             > >             > >     >         > demarcate
    > > >             > >             > >     >         >     > >> the
    > > >             > >             > >     >         >     > >> > header in
    > > >             > >             > >     >         >     > >> >         >>
    > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > core message.
    > > >             > > Then the header
    > > >             > >             > > byte
    > > >             > >             > >     > array in the
    > > >             > >             > >     >         > core
    > > >             > >             > >     >         >     > >> > message is
    > an
    > > >             > >             > >     >         >     > >> >         >>
    > > > array of
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > key, value
    > > >             > > pairs. This is what
    > > >             > >             > > it is
    > > >             > >             > >     > denoting.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > Then this
    > > >             > would
    > > >             > > be I guess in
    > > >             > >             > > the
    > > >             > >             > >     > given
    > > >             > >             > >     >         > notation:
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > Headers =>
    > > >             > > [KeyLength, Key,
    > > >             > >             > >     > ValueLength, Value]
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     KeyLength
    > > >             > > => int32
    > > >             > >             > >     > <-----------------NEW
    > > >             > >             > >     >         > size of
    > > >             > >             > >     >         >     > the
    > > >             > >             > >     >         >     > >> > byte[] of
    > > >             > >             > >     >         >     > >> >         >>
    > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > serialised key
    > > >             > > value
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     Key =>
    > > >             > bytes
    > > >             > >             > >     > <---------------------- NEW
    > > >             > >             > >     >         >     > serialised
    > > >             > >             > >     >         >     > >> > string
    > (UTF8)
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > bytes of the
    > > >             > > header key
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             >  ValueLength
    > > >             > > => int32
    > > >             > >             > >     > <-------------- NEW
    > > >             > >             > >     >         > size of
    > > >             > >             > >     >         >     > the
    > > >             > >             > >     >         >     > >> > byte[] of
    > > >             > >             > >     >         >     > >> >         >>
    > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > serialised
    > > >             > > header value
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     Value =>
    > > >             > > bytes
    > > >             > >             > >     > <-------------------- NEW
    > > >             > >             > >     >         >     > serialised
    > > >             > >             > >     >         >     > >> > form of the
    > > >             > >             > >     >         >     > >> >         >>
    > > > header
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > value
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > The key length
    > > >             > > and value
    > > >             > >             > length
    > > >             > >             > > is
    > > >             > >             > >     > matching the
    > > >             > >             > >     >         > way
    > > >             > >             > >     >         >     > the
    > > >             > >             > >     >         >     > >> > protocol is
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > defined in the
    > > >             > > core message
    > > >             > >             > > currently.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > On point 2)
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > Var sized
    > > >             > ints,
    > > >             > > this was
    > > >             > >             > > discussed
    > > >             > >             > >     > much earlier
    > > >             > >             > >     >         > on, in
    > > >             > >             > >     >         >     > >> > fact I had
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > suggested it
    > > >             > > myself (with
    > > >             > >             > Hadoop
    > > >             > >             > >     > references),
    > > >             > >             > >     >         > the
    > > >             > >             > >     >         >     > >> > complexity
    > of
    > > > this
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > compared to
    > > >             > > having a simpler
    > > >             > >             > > protocol
    > > >             > >             > >     > was
    > > >             > >             > >     >         > argued and
    > > >             > >             > >     >         >     > >> > agreed it
    > > >             > >             > >     >         >     > >> >         >>
    > > > wasn’t worth
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > the complexity
    > > >             > > as all other
    > > >             > >             > > clients
    > > >             > >             > >     > in other
    > > >             > >             > >     >         > languages
    > > >             > >             > >     >         >     > >> > would need
    > to
    > > >             > >             > >     >         >     > >> >         >>
    > > > ensure
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > theyre using
    > > >             > > the right var
    > > >             > >             > size
    > > >             > >             > >     > algorithm, as
    > > >             > >             > >     >         > there
    > > >             > >             > >     >         >     > is a
    > > >             > >             > >     >         >     > >> > few.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > On point 3)
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > We did the
    > > >             > > attributes,
    > > >             > >             > optional
    > > >             > >             > >     > approach as
    > > >             > >             > >     >         > originally
    > > >             > >             > >     >         >     > >> > there was
    > > >             > >             > >     >         >     > >> >         >>
    > > > marked
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > concern that
    > > >             > > headers would
    > > >             > >             > > cause a
    > > >             > >             > >     > message size
    > > >             > >             > >     >         >     > overhead
    > > >             > >             > >     >         >     > >> > for others,
    > > >             > >             > >     >         >     > >> >         >>
    > who
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > don’t want
    > > >             > > them. As such this
    > > >             > >             > > is the
    > > >             > >             > >     > clean
    > > >             > >             > >     >         > solution to
    > > >             > >             > >     >         >     > >> > achieve
    > that.
    > > >             > >             > >     >         >     > >> >         >>
    > If
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > that no longer
    > > >             > > holds, and we
    > > >             > >             > > don’t
    > > >             > >             > >     > care that we
    > > >             > >             > >     >         > add
    > > >             > >             > >     >         >     > >> 4bytes
    > > >             > >             > >     >         >     > >> > overhead,
    > > >             > >             > >     >         >     > >> >         >>
    > > then
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > im happy to
    > > >             > > remove.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > I’m personally
    > > >             > > in favour of
    > > >             > >             > > keeping
    > > >             > >             > >     > the message
    > > >             > >             > >     >         > as
    > > >             > >             > >     >         >     > small
    > > >             > >             > >     >         >     > >> > as possible
    > > >             > >             > >     >         >     > >> >         >>
    > so
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > people don’t
    > > >             > > get shocks in
    > > >             > >             > perf
    > > >             > >             > > and
    > > >             > >             > >     > throughputs
    > > >             > >             > >     >         > dues
    > > >             > >             > >     >         >     > to
    > > >             > >             > >     >         >     > >> > message
    > size,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > unless they
    > > >             > > actively use the
    > > >             > >             > > feature,
    > > >             > >             > >     > as such I
    > > >             > >             > >     >         > do
    > > >             > >             > >     >         >     > >> prefer
    > > >             > >             > >     >         >     > >> > the
    > > >             > >             > >     >         >     > >> >         >>
    > > > attribute bit
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > wise feature
    > > >             > > flag approach
    > > >             > >             > > myself.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > On 16/02/2017,
    > > >             > > 05:40, "Jason
    > > >             > >             > >     > Gustafson" <
    > > >             > >             > >     >         >     > >> >
    > > > jason@confluent.io> wrote:
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     We have
    > > >             > > proposed a few
    > > >             > >             > >     > significant changes
    > > >             > >             > >     >         > to the
    > > >             > >             > >     >         >     > >> > message
    > format
    > > >             > >             > >     >         >     > >> >         >>
    > in
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > KIP-98
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     which now
    > > >             > > seems likely to
    > > >             > >             > > pass
    > > >             > >             > >     > (perhaps
    > > >             > >             > >     >         > with some
    > > >             > >             > >     >         >     > >> > iterations
    > on
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >  implementation details).
    > > >             > >             > It
    > > >             > >             > > would
    > > >             > >             > >     > be good
    > > >             > >             > >     >         > to try
    > > >             > >             > >     >         >     > and
    > > >             > >             > >     >         >     > >> > coordinate
    > > >             > >             > >     >         >     > >> >         >>
    > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > changes
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     in both of
    > > >             > > the proposals
    > > >             > >             > to
    > > >             > >             > > make
    > > >             > >             > >     > sure they
    > > >             > >             > >     >         > are
    > > >             > >             > >     >         >     > >> > consistent
    > and
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > compatible.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     I think
    > > >             > > using the
    > > >             > >             > > attributes to
    > > >             > >             > >     > indicate
    > > >             > >             > >     >         > null
    > > >             > >             > >     >         >     > >> headers
    > > >             > >             > >     >         >     > >> > is a
    > > >             > >             > >     >         >     > >> >         >>
    > > > reasonable
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     approach.
    > > >             > > We have proposed
    > > >             > >             > > to do
    > > >             > >             > >     > the same
    > > >             > >             > >     >         > thing
    > > >             > >             > >     >         >     > for
    > > >             > >             > >     >         >     > >> > the message
    > > >             > >             > >     >         >     > >> >         >>
    > key
    > > > and
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     value.
    > > >             > That
    > > >             > > said, I
    > > >             > >             > > sympathize
    > > >             > >             > >     > with Jay's
    > > >             > >             > >     >         >     > argument.
    > > >             > >             > >     >         >     > >> > Having
    > > >             > >             > >     >         >     > >> >         >>
    > > > multiple
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > ways to
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     specify a
    > > >             > > null value
    > > >             > >             > > increases
    > > >             > >             > >     > the overall
    > > >             > >             > >     >         >     > >> complexity
    > > >             > >             > >     >         >     > >> > of the
    > > >             > >             > >     >         >     > >> >         >>
    > > > protocol.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > You
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     can see
    > > >             > > this just from the
    > > >             > >             > > fact
    > > >             > >             > >     > that you
    > > >             > >             > >     >         > need the
    > > >             > >             > >     >         >     > >> > extra
    > verbiage
    > > >             > >             > >     >         >     > >> >         >>
    > in
    > > > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     protocol
    > > >             > > specification in
    > > >             > >             > > this
    > > >             > >             > >     > KIP and in
    > > >             > >             > >     >         > KIP-98
    > > >             > >             > >     >         >     > to
    > > >             > >             > >     >         >     > >> > describe the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > dependence
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     between
    > > >             > the
    > > >             > > fields and the
    > > >             > >             > >     > attributes. It
    > > >             > >             > >     >         > seems
    > > >             > >             > >     >         >     > >> like a
    > > >             > >             > >     >         >     > >> > slippery
    > > >             > >             > >     >         >     > >> >         >>
    > > slope
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > if
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     you start
    > > >             > > allowing
    > > >             > >             > different
    > > >             > >             > >     > request types
    > > >             > >             > >     >         > to
    > > >             > >             > >     >         >     > >> > implement
    > the
    > > >             > >             > >     >         >     > >> >         >>
    > > > protocol
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >  specification differently.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     You can
    > > >             > > also argue that
    > > >             > >             > the
    > > >             > >             > >     > messages
    > > >             > >             > >     >         > already are
    > > >             > >             > >     >         >     > and
    > > >             > >             > >     >         >     > >> > are likely
    > > >             > >             > >     >         >     > >> >         >>
    > to
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > remain a
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     special
    > > >             > > case. For example,
    > > >             > >             > > there
    > > >             > >             > >     > is
    > > >             > >             > >     >         > currently no
    > > >             > >             > >     >         >     > >> > generality
    > in
    > > >             > >             > >     >         >     > >> >         >>
    > how
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     compressed
    > > >             > > message sets
    > > >             > >             > are
    > > >             > >             > >     > represented
    > > >             > >             > >     >         > that would
    > > >             > >             > >     >         >     > >> be
    > > >             > >             > >     >         >     > >> > applicable
    > > >             > >             > >     >         >     > >> >         >>
    > for
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > other
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     request
    > > >             > > types. Some might
    > > >             > >             > > see this
    > > >             > >             > >     >         > divergence as
    > > >             > >             > >     >         >     > an
    > > >             > >             > >     >         >     > >> > unfortunate
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > protocol
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     deficiency
    > > >             > > which should be
    > > >             > >             > > fixed;
    > > >             > >             > >     > others
    > > >             > >             > >     >         > might see
    > > >             > >             > >     >         >     > >> it
    > > >             > >             > >     >         >     > >> > as sort of
    > > >             > >             > >     >         >     > >> >         >>
    > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >  inevitability of needing
    > > >             > >             > to
    > > >             > >             > >     > optimize where
    > > >             > >             > >     >         > it
    > > >             > >             > >     >         >     > counts
    > > >             > >             > >     >         >     > >> > most. I'm
    > > >             > >             > >     >         >     > >> >         >>
    > > > probably
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     somewhere
    > > >             > > in between, but
    > > >             > >             > I
    > > >             > >             > > think
    > > >             > >             > >     > we
    > > >             > >             > >     >         > probably all
    > > >             > >             > >     >         >     > >> > share the
    > > >             > >             > >     >         >     > >> >         >>
    > > > intuition
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > that
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     the
    > > >             > > protocol should be
    > > >             > >             > kept
    > > >             > >             > > as
    > > >             > >             > >     > consistent as
    > > >             > >             > >     >         >     > >> possible.
    > > >             > >             > >     >         >     > >> > With that
    > > >             > >             > >     >         >     > >> >         >>
    > in
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > mind,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     here are a
    > > >             > > few comments:
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     1. One
    > > >             > > thing I found a
    > > >             > >             > > little odd
    > > >             > >             > >     > when
    > > >             > >             > >     >         > reading the
    > > >             > >             > >     >         >     > >> > current
    > > >             > >             > >     >         >     > >> >         >>
    > > > proposal is
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > that
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     the
    > > >             > headers
    > > >             > > are both
    > > >             > >             > > represented
    > > >             > >             > >     > as an
    > > >             > >             > >     >         > array of
    > > >             > >             > >     >         >     > >> bytes
    > > >             > >             > >     >         >     > >> > and as an
    > > >             > >             > >     >         >     > >> >         >>
    > > array
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > of
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     key/value
    > > >             > > pairs. I'd
    > > >             > >             > > probably
    > > >             > >             > >     > suggest
    > > >             > >             > >     >         > something
    > > >             > >             > >     >         >     > like
    > > >             > >             > >     >         >     > >> > this:
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     Headers =>
    > > >             > > [HeaderKey
    > > >             > >             > > HeaderValue]
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >      HeaderKey
    > > >             > > => String
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > > HeaderValue => Bytes
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     An array
    > > >             > in
    > > >             > > the Kafka
    > > >             > >             > > protocol is
    > > >             > >             > >     >         > represented as a
    > > >             > >             > >     >         >     > >> > 4-byte
    > integer
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     indicating
    > > >             > > the number of
    > > >             > >             > > elements
    > > >             > >             > >     > in the
    > > >             > >             > >     >         > array
    > > >             > >             > >     >         >     > >> > followed by
    > > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >  serialization of the
    > > >             > >             > > elements.
    > > >             > >             > >     > Unless I'm
    > > >             > >             > >     >         >     > >> >
    > > > misunderstanding, what
    > > >             > >             > >     >         >     > >> >         >>
    > you
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > have
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     instead is
    > > >             > > the total size
    > > >             > >             > > of the
    > > >             > >             > >     > headers in
    > > >             > >             > >     >         > bytes
    > > >             > >             > >     >         >     > >> > followed by
    > > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > elements.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     I'm not
    > > >             > > sure I see any
    > > >             > >             > > reason for
    > > >             > >             > >     > this
    > > >             > >             > >     >         >     > >> inconsistency.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     2. In
    > > >             > > KIP-98, we've
    > > >             > >             > > introduced
    > > >             > >             > >     >         > variable-length
    > > >             > >             > >     >         >     > >> integer
    > > >             > >             > >     >         >     > >> > fields.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > Effectively,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     we've
    > > >             > > enriched (or
    > > >             > >             > > "complicated"
    > > >             > >             > >     > as Jay
    > > >             > >             > >     >         > might say
    > > >             > >             > >     >         >     > ;)
    > > >             > >             > >     >         >     > >> > the protocol
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >  specification to include
    > > >             > >             > the
    > > >             > >             > >     > following
    > > >             > >             > >     >         > types:
    > > >             > >             > >     >         >     > >> VarInt,
    > > >             > >             > >     >         >     > >> > VarLong,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >  UnsignedVarInt and
    > > >             > >             > >     > UnsignedVarLong.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     Along with
    > > >             > > these
    > > >             > >             > > primitives, we
    > > >             > >             > >     > could
    > > >             > >             > >     >         > introduce
    > > >             > >             > >     >         >     > the
    > > >             > >             > >     >         >     > >> > following
    > > >             > >             > >     >         >     > >> >         >>
    > > > types:
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >  VarSizeArray =>
    > > >             > >             > > NumberOfItems
    > > >             > >             > >     > Item1 Item2
    > > >             > >             > >     >         > .. ItemN
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >  NumberOfItems =>
    > > >             > >             > > UnsignedVarInt
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >  VarSizeNullableArray =>
    > > >             > >             > >     > NumberOfItemsOrNull
    > > >             > >             > >     >         > Item1
    > > >             > >             > >     >         >     > >> > Item2 ..
    > ItemN
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >  NumberOfItemsOrNull =>
    > > >             > >             > > VarInt
    > > >             > >             > >     > (-1 means
    > > >             > >             > >     >         > null)
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     And
    > > >             > > similarly for the
    > > >             > >             > > `String`
    > > >             > >             > >     > and `Bytes`
    > > >             > >             > >     >         > types.
    > > >             > >             > >     >         >     > >> > These types
    > > >             > >             > >     >         >     > >> >         >>
    > can
    > > > save
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > a
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >  considerable amount of
    > > >             > >             > > space in
    > > >             > >             > >     > this
    > > >             > >             > >     >         > proposal
    > > >             > >             > >     >         >     > >> because
    > > >             > >             > >     >         >     > >> > they can
    > > >             > >             > >     >         >     > >> >         >>
    > be
    > > > used
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > for
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     both the
    > > >             > > number of headers
    > > >             > >             > >     > included in the
    > > >             > >             > >     >         > message
    > > >             > >             > >     >         >     > >> and
    > > >             > >             > >     >         >     > >> > the
    > > >             > >             > >     >         >     > >> >         >>
    > > > lengths of
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     header
    > > >             > keys
    > > >             > > and values. We
    > > >             > >             > > could
    > > >             > >             > >     > do this
    > > >             > >             > >     >         > instead:
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     Headers =>
    > > >             > >             > > VarSizeArray[HeaderKey
    > > >             > >             > >     >         > HeaderValue]
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             >  HeaderKey
    > > >             > > =>
    > > >             > >             > VarSizeString
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >  HeaderValue =>
    > > >             > >             > > VarSizeBytes
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     Combining
    > > >             > > the savings from
    > > >             > >             > > the
    > > >             > >             > >     > use of
    > > >             > >             > >     >         > variable
    > > >             > >             > >     >         >     > >> length
    > > >             > >             > >     >         >     > >> > fields, the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > benefit
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     of using
    > > >             > > the attributes to
    > > >             > >             > >     > represent null
    > > >             > >             > >     >         > seems
    > > >             > >             > >     >         >     > >> pretty
    > > >             > >             > >     >         >     > >> > small.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     3.
    > > >             > > Whichever way we go
    > > >             > >             > > (whether
    > > >             > >             > >     > we use the
    > > >             > >             > >     >         >     > >> attributes
    > > >             > >             > >     >         >     > >> > or not), we
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > should at
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     least be
    > > >             > > consistent
    > > >             > >             > between
    > > >             > >             > > this
    > > >             > >             > >     > KIP and
    > > >             > >             > >     >         > KIP-98.
    > > >             > >             > >     >         >     > It
    > > >             > >             > >     >         >     > >> > would be
    > very
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > strange
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     to have
    > > >             > two
    > > >             > > ways to
    > > >             > >             > > represent
    > > >             > >             > >     > null values
    > > >             > >             > >     >         > in the
    > > >             > >             > >     >         >     > >> same
    > > >             > >             > >     >         >     > >> > schema.
    > > >             > >             > >     >         >     > >> >         >>
    > > > Either
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > way is
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     OK with
    > > >             > me.
    > > >             > > I think some
    > > >             > >             > >     > message-level
    > > >             > >             > >     >         >     > optimizations
    > > >             > >             > >     >         >     > >> > are
    > > >             > >             > >     >         >     > >> >         >>
    > > > justifiable,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > but
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     the
    > > >             > savings
    > > >             > > here seem
    > > >             > >             > > minimal (a
    > > >             > >             > >     > few bytes
    > > >             > >             > >     >         > per
    > > >             > >             > >     >         >     > >> > message), so
    > > >             > >             > >     >         >     > >> >         >>
    > > > maybe it's
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > not
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     worth the
    > > >             > > cost of letting
    > > >             > >             > > the
    > > >             > >             > >     > message
    > > >             > >             > >     >         > diverge even
    > > >             > >             > >     >         >     > >> > further from
    > > >             > >             > >     >         >     > >> >         >>
    > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > rest of
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     the
    > > >             > > protocol.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     -Jason
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     On Wed,
    > > >             > Feb
    > > >             > > 15, 2017 at
    > > >             > >             > > 8:52 AM,
    > > >             > >             > >     > radai <
    > > >             > >             > >     >         >     > >> >         >>
    > > >             > > radai.rosenblatt@gmail.com>
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > wrote:
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > I've
    > > >             > > trimmed the inline
    > > >             > >             > >     > contents as this
    > > >             > >             > >     >         > mail is
    > > >             > >             > >     >         >     > >> > getting too
    > > >             > >             > >     >         >     > >> >         >>
    > big
    > > > for
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > apache
    > > >             > > mailing list
    > > >             > >             > > software to
    > > >             > >             > >     > deliver
    > > >             > >             > >     >         > :-(
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > 1. the
    > > >             > > important thing
    > > >             > >             > for
    > > >             > >             > >     >         > interoperability is
    > > >             > >             > >     >         >     > for
    > > >             > >             > >     >         >     > >> > different
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > "interested
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > parties"
    > > >             > > (plugins, infra
    > > >             > >             > >     > layers/wrappers,
    > > >             > >             > >     >         >     > >> user-code)
    > > >             > >             > >     >         >     > >> > to be
    > > >             > >             > >     >         >     > >> >         >>
    > > able
    > > > to
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > stick
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > pieces
    > > >             > of
    > > >             > > metadata onto
    > > >             > >             > > msgs
    > > >             > >             > >     > without
    > > >             > >             > >     >         > getting in
    > > >             > >             > >     >         >     > >> each
    > > >             > >             > >     >         >     > >> > other's
    > > >             > >             > >     >         >     > >> >         >>
    > > way.
    > > > a
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > common
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > key
    > > >             > > scheme (Strings, as
    > > >             > >             > > of the
    > > >             > >             > >     > time of
    > > >             > >             > >     >         > this
    > > >             > >             > >     >         >     > >> > writing?) is
    > > all
    > > >             > >             > >     >         >     > >> >         >>
    > > thats
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > required
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > for
    > > >             > that.
    > > >             > > it is assumed
    > > >             > >             > > that
    > > >             > >             > >     > the other end
    > > >             > >             > >     >         >     > >> > interested
    > in
    > > > any
    > > >             > >             > >     >         >     > >> >         >>
    > > such
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > piece of
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > metadata
    > > >             > > knows the
    > > >             > >             > > encoding,
    > > >             > >             > >     > and byte[]
    > > >             > >             > >     >         > provides
    > > >             > >             > >     >         >     > >> for
    > > >             > >             > >     >         >     > >> > the most
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > flexibility.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > i
    > > >             > believe
    > > >             > > this is the
    > > >             > >             > same
    > > >             > >             > >     > logic behind
    > > >             > >             > >     >         > core
    > > >             > >             > >     >         >     > kafka
    > > >             > >             > >     >         >     > >> > being
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > byte[]/byte[]
    > > >             > -
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > Strings
    > > >             > > are more
    > > >             > >             > "usable"
    > > >             > >             > > but
    > > >             > >             > >     > bytes are
    > > >             > >             > >     >         > flexible
    > > >             > >             > >     >         >     > >> and
    > > >             > >             > >     >         >     > >> > so were
    > > >             > >             > >     >         >     > >> >         >>
    > > > chosen.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > Also -
    > > >             > > core kafka doesnt
    > > >             > >             > > even
    > > >             > >             > >     > do that
    > > >             > >             > >     >         > good of a
    > > >             > >             > >     >         >     > >> job
    > > >             > >             > >     >         >     > >> > on
    > > >             > >             > >     >         >     > >> >         >>
    > > > usability of
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > payload
    > > >             > > (example - i
    > > >             > >             > have
    > > >             > >             > > to
    > > >             > >             > >     > specify the
    > > >             > >             > >     >         > nop
    > > >             > >             > >     >         >     > >> byte[]
    > > >             > >             > >     >         >     > >> > "decoders"
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > explicitly
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > in
    > > >             > conf),
    > > >             > > and again
    > > >             > >             > > sacrificies
    > > >             > >             > >     > usability
    > > >             > >             > >     >         > for
    > > >             > >             > >     >         >     > the
    > > >             > >             > >     >         >     > >> > sake of
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > performance
    > > >             > (no
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     >
    > > >             > > convenient single-record
    > > >             > >             > >     > processing as
    > > >             > >             > >     >         > poll is a
    > > >             > >             > >     >         >     > >> > batch, lots
    > of
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > obscure
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > little
    > > >             > > config details
    > > >             > >             > > exposing
    > > >             > >             > >     > internals
    > > >             > >             > >     >         > of the
    > > >             > >             > >     >         >     > >> > batching
    > > >             > >             > >     >         >     > >> >         >>
    > > > mechanism,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > etc)
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > this is
    > > >             > > also why i
    > > >             > >             > really
    > > >             > >             > >     > dislike the
    > > >             > >             > >     >         > idea of a
    > > >             > >             > >     >         >     > >> > "type
    > system"
    > > >             > >             > >     >         >     > >> >         >>
    > for
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > header
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > values,
    > > >             > > it further
    > > >             > >             > > degrades the
    > > >             > >             > >     >         > usability, adds
    > > >             > >             > >     >         >     > >> > complexity
    > and
    > > >             > >             > >     >         >     > >> >         >>
    > > will
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     >
    > > >             > > eventually get in
    > > >             > >             > > people's way,
    > > >             > >             > >     > also, it
    > > >             > >             > >     >         > would
    > > >             > >             > >     >         >     > be
    > > >             > >             > >     >         >     > >> > the 2nd/3rd
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > home-group
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     >
    > > >             > > serialization mechanism
    > > >             > >             > > in core
    > > >             > >             > >     > kafka
    > > >             > >             > >     >         > (counting
    > > >             > >             > >     >         >     > 2
    > > >             > >             > >     >         >     > >> > iterations
    > > >             > >             > >     >         >     > >> >         >>
    > of
    > > > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > "type
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     >
    > > >             > > definition DSL")
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > 2. this
    > > >             > > is an
    > > >             > >             > > implementation
    > > >             > >             > >     > detail, and
    > > >             > >             > >     >         > not
    > > >             > >             > >     >         >     > even
    > > >             > >             > >     >         >     > >> a
    > > >             > >             > >     >         >     > >> > very "user
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > facing" one?
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > to the
    > > >             > > best of my
    > > >             > >             > > understanding
    > > >             > >             > >     > the vote
    > > >             > >             > >     >         > process
    > > >             > >             > >     >         >     > >> is
    > > >             > >             > >     >         >     > >> > on proposed
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     >
    > > >             > > API/behaviour. also -
    > > >             > >             > > since
    > > >             > >             > >     > we're willing
    > > >             > >             > >     >         > to go
    > > >             > >             > >     >         >     > >> with
    > > >             > >             > >     >         >     > >> > strings
    > > >             > >             > >     >         >     > >> >         >>
    > > just
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > serialize
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > a
    > > >             > 0-sized
    > > >             > > header blob
    > > >             > >             > and
    > > >             > >             > > IIUC
    > > >             > >             > >     > you dont
    > > >             > >             > >     >         > need any
    > > >             > >             > >     >         >     > >> > optionals
    > > >             > >             > >     >         >     > >> >         >>
    > > > anymore.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > 3. yes,
    > > >             > > we can :-)
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > On Tue,
    > > >             > > Feb 14, 2017 at
    > > >             > >             > > 11:56
    > > >             > >             > >     > PM, Michael
    > > >             > >             > >     >         >     > Pearce <
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > > Michael.Pearce@ig.com>
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > wrote:
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > Hi
    > > >             > Jay,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > 1)
    > > >             > > There was some
    > > >             > >             > > initial
    > > >             > >             > >     > debate on the
    > > >             > >             > >     >         > value
    > > >             > >             > >     >         >     > >> > part, as
    > youll
    > > >             > >             > >     >         >     > >> >         >>
    > > note
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > String,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > String
    > > >             > > headers were
    > > >             > >             > >     > discounted early
    > > >             > >             > >     >         > on. The
    > > >             > >             > >     >         >     > >> > reason for
    > > this
    > > >             > >             > >     >         >     > >> >         >>
    > is
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     >
    > > >             > > flexibility
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > and
    > > >             > > keeping in line
    > > >             > >             > > with the
    > > >             > >             > >     >         > flexibility of
    > > >             > >             > >     >         >     > key,
    > > >             > >             > >     >         >     > >> > value of the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > message
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > object
    > > >             > > itself. I don’t
    > > >             > >             > > think
    > > >             > >             > >     > it takes
    > > >             > >             > >     >         > away
    > > >             > >             > >     >         >     > from
    > > >             > >             > >     >         >     > >> an
    > > >             > >             > >     >         >     > >> > ecosystem
    > > >             > >             > >     >         >     > >> >         >>
    > as
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > each
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > plugin
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > will
    > > >             > > care for their
    > > >             > >             > own
    > > >             > >             > > key,
    > > >             > >             > >     > this way
    > > >             > >             > >     >         > ints,
    > > >             > >             > >     >         >     > >> > booleans ,
    > > > exotic
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > custom
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > binary
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > can
    > > >             > all
    > > >             > > be catered
    > > >             > >             > for=.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > a. If
    > > >             > > you really
    > > >             > >             > wanted
    > > >             > >             > > to
    > > >             > >             > >     > push for a
    > > >             > >             > >     >         > typed
    > > >             > >             > >     >         >     > >> value
    > > >             > >             > >     >         >     > >> > interface,
    > > >             > >             > >     >         >     > >> >         >> I
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > wouldn’t
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > want
    > > >             > > just String
    > > >             > >             > values
    > > >             > >             > >     > supported, but
    > > >             > >             > >     >         > the the
    > > >             > >             > >     >         >     > >> > primatives
    > > >             > >             > >     >         >     > >> >         >>
    > > plus
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > string and
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > also
    > > >             > > still keeping the
    > > >             > >             > >     > ability to have a
    > > >             > >             > >     >         >     > binary
    > > >             > >             > >     >         >     > >> > for custom
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > binaries that
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > some
    > > >             > > organisations may
    > > >             > >             > > have.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > i. I
    > > >             > > have written this
    > > >             > >             > > slight
    > > >             > >             > >     >         > alternative
    > > >             > >             > >     >         >     > here,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     >
    > > >             > >             > https://cwiki.apache.org/
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > >             > > confluence/display/KAFKA/KIP-
    > > >             > >             > >     >         >     > >> >
    > > > 82+-+Add+Record+Headers+-+
    > > >             > Typed
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > ii.
    > > >             > > Essentially the
    > > >             > >             > > value
    > > >             > >             > >     > bytes, has a
    > > >             > >             > >     >         > leading
    > > >             > >             > >     >         >     > >> > byte
    > overhead.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > 1.
    > > >             > > This tells you
    > > >             > >             > what
    > > >             > >             > > type
    > > >             > >             > >     > the value
    > > >             > >             > >     >         > is,
    > > >             > >             > >     >         >     > >> before
    > > >             > >             > >     >         >     > >> > reading
    > > >             > >             > >     >         >     > >> >         >>
    > the
    > > > rest
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > of the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > bytes,
    > > >             > > allowing
    > > >             > >             > >     >         >
    > > > serialisation/deserialization
    > > >             > >             > >     >         >     > to
    > > >             > >             > >     >         >     > >> > and from the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > primitives,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > string
    > > >             > > and byte[].
    > > >             > >             > This
    > > >             > >             > > is
    > > >             > >             > >     > akin to some
    > > >             > >             > >     >         > other
    > > >             > >             > >     >         >     > >> > messaging
    > > >             > >             > >     >         >     > >> >         >>
    > > > systems.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > 2) We
    > > >             > > are making it
    > > >             > >             > > optional,
    > > >             > >             > >     > so that
    > > >             > >             > >     >         > for
    > > >             > >             > >     >         >     > those
    > > >             > >             > >     >         >     > >> > not wanting
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > headers have
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > 0
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > bytes
    > > >             > > overhead (think
    > > >             > >             > > of it
    > > >             > >             > >     > as a feature
    > > >             > >             > >     >         >     > flag),
    > > >             > >             > >     >         >     > >> I
    > > >             > >             > >     >         >     > >> > don’t
    > > >             > >             > >     >         >     > >> >         >>
    > > > think this
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > is
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > > complex, especially if
    > > >             > >             > >     > comparing to
    > > >             > >             > >     >         > changes
    > > >             > >             > >     >         >     > >> > proposed in
    > > >             > >             > >     >         >     > >> >         >>
    > > > other kips
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > like
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > kip-98.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > a. If
    > > >             > > you really
    > > >             > >             > really
    > > >             > >             > > don’t
    > > >             > >             > >     > like
    > > >             > >             > >     >         > this, we
    > > >             > >             > >     >         >     > can
    > > >             > >             > >     >         >     > >> > drop it, but
    > > >             > >             > >     >         >     > >> >         >>
    > it
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > would
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > mean
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > buying
    > > >             > > into 4 bytes
    > > >             > >             > > extra
    > > >             > >             > >     > overhead for
    > > >             > >             > >     >         > users
    > > >             > >             > >     >         >     > who
    > > >             > >             > >     >         >     > >> > do not want
    > > >             > >             > >     >         >     > >> >         >>
    > to
    > > > use
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > headers.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > 3) In
    > > >             > > the summary yes,
    > > >             > >             > > it is
    > > >             > >             > >     > at a higher
    > > >             > >             > >     >         >     > level,
    > > >             > >             > >     >         >     > >> > but I think
    > > >             > >             > >     >         >     > >> >         >>
    > > this
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > is well
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > > documented in the
    > > >             > >             > > proposed
    > > >             > >             > >     > changes
    > > >             > >             > >     >         > section.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > a.
    > > >             > > Added getHeaders
    > > >             > >             > > method to
    > > >             > >             > >     >         >     > Producer/Consumer
    > > >             > >             > >     >         >     > >> > record (that
    > > >             > >             > >     >         >     > >> >         >>
    > is
    > > > it)
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > b.
    > > >             > > We’ve also detailed
    > > >             > >             > > the
    > > >             > >             > >     > new Headers
    > > >             > >             > >     >         > class
    > > >             > >             > >     >         >     > >> that
    > > >             > >             > >     >         >     > >> > this method
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > returns
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > that
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > > encapsulates the
    > > >             > >             > headers
    > > >             > >             > >     > protocol and
    > > >             > >             > >     >         > logic.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > Best,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > Mike
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > > ==Original questions
    > > >             > >             > > from the
    > > >             > >             > >     > vote
    > > >             > >             > >     >         > thread from
    > > >             > >             > >     >         >     > >> > Jay.==
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > Couple
    > > >             > > of things I
    > > >             > >             > > think we
    > > >             > >             > >     > still need
    > > >             > >             > >     >         > to work
    > > >             > >             > >     >         >     > >> out:
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >    1.
    > > >             > I
    > > >             > > think we agree
    > > >             > >             > > about
    > > >             > >             > >     > the key,
    > > >             > >             > >     >         > but I
    > > >             > >             > >     >         >     > >> think
    > > >             > >             > >     >         >     > >> > we haven't
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > talked about
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >    the
    > > >             > > value yet. I
    > > >             > >             > > think if
    > > >             > >             > >     > our goal
    > > >             > >             > >     >         > is an
    > > >             > >             > >     >         >     > open
    > > >             > >             > >     >         >     > >> > ecosystem
    > > >             > >             > >     >         >     > >> >         >>
    > of
    > > > these
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > header
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > > spread across many
    > > >             > >             > > plugins
    > > >             > >             > >     > from many
    > > >             > >             > >     >         >     > systems
    > > >             > >             > >     >         >     > >> we
    > > >             > >             > >     >         >     > >> > should
    > > >             > >             > >     >         >     > >> >         >>
    > > > consider
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > making
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > this
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >    a
    > > >             > > string as well so
    > > >             > >             > > it can
    > > >             > >             > >     > be
    > > >             > >             > >     >         > printed, set
    > > >             > >             > >     >         >     > >> via
    > > >             > >             > >     >         >     > >> > a UI, set
    > > >             > >             > >     >         >     > >> >         >>
    > in
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > config,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > etc.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > > Basically
    > > >             > >             > encouraging
    > > >             > >             > >     > pluggable
    > > >             > >             > >     >         >     > serialization
    > > >             > >             > >     >         >     > >> > formats
    > > >             > >             > >     >         >     > >> >         >>
    > > here
    > > > will
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > lead
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > to
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > a
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >    bit
    > > >             > > of a tower of
    > > >             > >             > > babel.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >    2.
    > > >             > > This proposal
    > > >             > >             > > still
    > > >             > >             > >     > includes a
    > > >             > >             > >     >         > pretty
    > > >             > >             > >     >         >     > big
    > > >             > >             > >     >         >     > >> > change to
    > our
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     >
    > > >             > > serialization
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >    and
    > > >             > > protocol
    > > >             > >             > > definition
    > > >             > >             > >     > layer.
    > > >             > >             > >     >         > Essentially
    > > >             > >             > >     >         >     > >> it is
    > > >             > >             > >     >         >     > >> >         >>
    > > > introducing an
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > optional
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > > type, where the
    > > >             > >             > > format is
    > > >             > >             > >     > data
    > > >             > >             > >     >         > dependent. I
    > > >             > >             > >     >         >     > >> > think this
    > is
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > actually a
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > big
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > > change though it
    > > >             > >             > > doesn't
    > > >             > >             > >     > seem like
    > > >             > >             > >     >         > it. It
    > > >             > >             > >     >         >     > >> means
    > > >             > >             > >     >         >     > >> > you can no
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > longer
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > specify
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > this
    > > >             > > type with our
    > > >             > >             > > type
    > > >             > >             > >     > definition
    > > >             > >             > >     >         > DSL, and
    > > >             > >             > >     >         >     > >> > likewise it
    > > >             > >             > >     >         >     > >> >         >>
    > > > requires
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > custom
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > > handling in client
    > > >             > >             > > libs.
    > > >             > >             > >     > This isn't
    > > >             > >             > >     >         > a huge
    > > >             > >             > >     >         >     > >> > thing, since
    > > >             > >             > >     >         >     > >> >         >>
    > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > Record
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > > definition is
    > > >             > >             > custom
    > > >             > >             > >     > anyway, but I
    > > >             > >             > >     >         > think
    > > >             > >             > >     >         >     > this
    > > >             > >             > >     >         >     > >> > kind of
    > > >             > >             > >     >         >     > >> >         >>
    > > > protocol
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > > inconsistency is
    > > >             > >             > very
    > > >             > >             > >     > non-desirable
    > > >             > >             > >     >         > and
    > > >             > >             > >     >         >     > ties
    > > >             > >             > >     >         >     > >> > you to
    > > >             > >             > >     >         >     > >> >         >>
    > > > hand-coding
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > things.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > I
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > > think the type
    > > >             > >             > should
    > > >             > >             > >     > instead by [Key
    > > >             > >             > >     >         >     > Value]
    > > >             > >             > >     >         >     > >> in
    > > >             > >             > >     >         >     > >> > our BNF,
    > > >             > >             > >     >         >     > >> >         >>
    > > where
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > key and
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > > value are both
    > > >             > >             > short
    > > >             > >             > >     > strings as used
    > > >             > >             > >     >         >     > >> elsewhere.
    > > >             > >             > >     >         >     > >> > This
    > > >             > >             > >     >         >     > >> >         >>
    > > > brings it
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > in line
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > with
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >    the
    > > >             > > rest of the
    > > >             > >             > > protocol.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >    3.
    > > >             > > Could we get
    > > >             > >             > more
    > > >             > >             > >     > specific about
    > > >             > >             > >     >         > the
    > > >             > >             > >     >         >     > exact
    > > >             > >             > >     >         >     > >> > Java API
    > > >             > >             > >     >         >     > >> >         >>
    > > > change to
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > > ProducerRecord,
    > > >             > >             > >     > ConsumerRecord,
    > > >             > >             > >     >         > Record,
    > > >             > >             > >     >         >     > etc?
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > > -Jay
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > > >     >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > The
    > > >             > information
    > > >             > > contained in
    > > >             > >             > > this
    > > >             > >             > >     > email is
    > > >             > >             > >     >         > strictly
    > > >             > >             > >     >         >     > >> > confidential
    > > and
    > > >             > >             > >     >         >     > >> >         >>
    > for
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > the use of the
    > > >             > > addressee only,
    > > >             > >             > > unless
    > > >             > >             > >     > otherwise
    > > >             > >             > >     >         >     > >> indicated.
    > > >             > >             > >     >         >     > >> > If you
    > > >             > >             > >     >         >     > >> >         >>
    > are
    > > > not
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > the intended
    > > >             > > recipient, please
    > > >             > >             > > do not
    > > >             > >             > >     > read,
    > > >             > >             > >     >         > copy, use
    > > >             > >             > >     >         >     > or
    > > >             > >             > >     >         >     > >> > disclose to
    > > >             > >             > >     >         >     > >> >         >>
    > > > others
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > this message
    > > >             > or
    > > >             > > any
    > > >             > >             > attachment.
    > > >             > >             > >     > Please also
    > > >             > >             > >     >         > notify the
    > > >             > >             > >     >         >     > >> > sender by
    > > >             > >             > >     >         >     > >> >         >>
    > > > replying
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > to this email
    > > >             > > or by telephone
    > > >             > >             > >     > (+44(020 7896
    > > >             > >             > >     >         > 0011) and
    > > >             > >             > >     >         >     > >> then
    > > >             > >             > >     >         >     > >> > delete
    > > >             > >             > >     >         >     > >> >         >>
    > the
    > > > email
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > and any copies
    > > >             > > of it.
    > > >             > >             > Opinions,
    > > >             > >             > >     > conclusion
    > > >             > >             > >     >         > (etc) that
    > > >             > >             > >     >         >     > do
    > > >             > >             > >     >         >     > >> > not relate
    > > >             > >             > >     >         >     > >> >         >>
    > to
    > > > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > official
    > > >             > > business of this
    > > >             > >             > > company
    > > >             > >             > >     > shall be
    > > >             > >             > >     >         > understood
    > > >             > >             > >     >         >     > as
    > > >             > >             > >     >         >     > >> > neither
    > > >             > >             > >     >         >     > >> >         >>
    > > > given nor
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > endorsed by
    > > >             > it.
    > > >             > > IG is a
    > > >             > >             > trading
    > > >             > >             > > name
    > > >             > >             > >     > of IG
    > > >             > >             > >     >         > Markets
    > > >             > >             > >     >         >     > >> Limited
    > > >             > >             > >     >         >     > >> > (a company
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > registered in
    > > >             > > England and
    > > >             > >             > Wales,
    > > >             > >             > >     > company number
    > > >             > >             > >     >         >     > >> 04008957)
    > > >             > >             > >     >         >     > >> > and IG
    > > >             > >             > >     >         >     > >> >         >>
    > > Index
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > Limited (a
    > > >             > > company registered
    > > >             > >             > in
    > > >             > >             > >     > England and
    > > >             > >             > >     >         > Wales,
    > > >             > >             > >     >         >     > >> > company
    > number
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > 01190902).
    > > >             > > Registered address
    > > >             > >             > at
    > > >             > >             > >     > Cannon Bridge
    > > >             > >             > >     >         > House,
    > > >             > >             > >     >         >     > 25
    > > >             > >             > >     >         >     > >> > Dowgate
    > > >             > >             > >     >         >     > >> >         >>
    > > Hill,
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > London EC4R
    > > >             > > 2YA. Both IG
    > > >             > >             > Markets
    > > >             > >             > >     > Limited
    > > >             > >             > >     >         > (register
    > > >             > >             > >     >         >     > >> number
    > > >             > >             > >     >         >     > >> > 195355)
    > > >             > >             > >     >         >     > >> >         >>
    > and
    > > > IG
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > Index Limited
    > > >             > > (register number
    > > >             > >             > >     > 114059) are
    > > >             > >             > >     >         > authorised
    > > >             > >             > >     >         >     > >> and
    > > >             > >             > >     >         >     > >> > regulated
    > > >             > >             > >     >         >     > >> >         >>
    > by
    > > > the
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > > Financial
    > > >             > > Conduct Authority.
    > > >             > >             > >     >         >     > >> >         >>
    > >>
    > > >
    > > >             > >             > >     >         >     > >> >         >>
    > > >             > >             > >     >         >     > >> >         >>
    > > >             > >             > >     >         >     > >> >         >>
    > > >             > >             > >     >         >     > >> >         >>
    > --
    > > >             > >             > >     >         >     > >> >         >>
    > > > Nacho - Ignacio
    > > >             > > Solis -
    > > >             > >             > > isolis@igso.net
    > > >             > >             > >     >         >     > >> >         >>
    > > >             > >             > >     >         >     > >> >         >
    > > >             > >             > >     >         >     > >> >         >
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> > The
    > > information
    > > > contained in
    > > >             > > this email is
    > > >             > >             > > strictly
    > > >             > >             > >     >         > confidential and
    > > >             > >             > >     >         >     > for
    > > >             > >             > >     >         >     > >> > the use of
    > the
    > > > addressee only,
    > > >             > > unless
    > > >             > >             > otherwise
    > > >             > >             > >     > indicated. If
    > > >             > >             > >     >         > you are
    > > >             > >             > >     >         >     > >> not
    > > >             > >             > >     >         >     > >> > the intended
    > > > recipient, please
    > > >             > > do not read,
    > > >             > >             > > copy, use
    > > >             > >             > >     > or
    > > >             > >             > >     >         > disclose to
    > > >             > >             > >     >         >     > >> others
    > > >             > >             > >     >         >     > >> > this message
    > > or
    > > > any
    > > >             > attachment.
    > > >             > > Please also
    > > >             > >             > > notify
    > > >             > >             > >     > the sender by
    > > >             > >             > >     >         >     > >> replying
    > > >             > >             > >     >         >     > >> > to this
    > email
    > > > or by telephone
    > > >             > > (+44(020 7896
    > > >             > >             > > 0011) and
    > > >             > >             > >     > then
    > > >             > >             > >     >         > delete the
    > > >             > >             > >     >         >     > >> email
    > > >             > >             > >     >         >     > >> > and any
    > copies
    > > > of it.
    > > >             > Opinions,
    > > >             > > conclusion
    > > >             > >             > > (etc) that
    > > >             > >             > >     > do not
    > > >             > >             > >     >         > relate to
    > > >             > >             > >     >         >     > >> the
    > > >             > >             > >     >         >     > >> > official
    > > > business of this
    > > >             > > company shall be
    > > >             > >             > > understood
    > > >             > >             > >     > as
    > > >             > >             > >     >         > neither given
    > > >             > >             > >     >         >     > >> nor
    > > >             > >             > >     >         >     > >> > endorsed by
    > > it.
    > > > IG is a
    > > >             > trading
    > > >             > > name of IG
    > > >             > >             > > Markets
    > > >             > >             > >     > Limited (a
    > > >             > >             > >     >         > company
    > > >             > >             > >     >         >     > >> > registered
    > in
    > > > England and
    > > >             > > Wales, company
    > > >             > >             > number
    > > >             > >             > >     > 04008957) and
    > > >             > >             > >     >         > IG Index
    > > >             > >             > >     >         >     > >> > Limited (a
    > > > company registered
    > > >             > > in England and
    > > >             > >             > > Wales,
    > > >             > >             > >     > company
    > > >             > >             > >     >         > number
    > > >             > >             > >     >         >     > >> > 01190902).
    > > > Registered address
    > > >             > > at Cannon Bridge
    > > >             > >             > > House,
    > > >             > >             > >     > 25
    > > >             > >             > >     >         > Dowgate Hill,
    > > >             > >             > >     >         >     > >> > London EC4R
    > > > 2YA. Both IG
    > > >             > > Markets Limited
    > > >             > >             > > (register
    > > >             > >             > >     > number
    > > >             > >             > >     >         > 195355) and
    > > >             > >             > >     >         >     > IG
    > > >             > >             > >     >         >     > >> > Index
    > Limited
    > > > (register number
    > > >             > > 114059) are
    > > >             > >             > > authorised
    > > >             > >             > >     > and
    > > >             > >             > >     >         > regulated by
    > > >             > >             > >     >         >     > >> the
    > > >             > >             > >     >         >     > >> > Financial
    > > > Conduct Authority.
    > > >             > >             > >     >         >     > >> >
    > > >             > >             > >     >         >     > >> The
    > information
    > > > contained in
    > > >             > this
    > > >             > > email is
    > > >             > >             > > strictly
    > > >             > >             > >     > confidential
    > > >             > >             > >     >         > and for
    > > >             > >             > >     >         >     > >> the use of the
    > > > addressee only,
    > > >             > > unless otherwise
    > > >             > >             > >     > indicated. If you
    > > >             > >             > >     >         > are
    > > >             > >             > >     >         >     > not
    > > >             > >             > >     >         >     > >> the intended
    > > > recipient, please
    > > >             > do
    > > >             > > not read,
    > > >             > >             > copy,
    > > >             > >             > > use
    > > >             > >             > >     > or disclose
    > > >             > >             > >     >         > to
    > > >             > >             > >     >         >     > others
    > > >             > >             > >     >         >     > >> this message
    > or
    > > > any attachment.
    > > >             > > Please also
    > > >             > >             > > notify the
    > > >             > >             > >     > sender by
    > > >             > >             > >     >         >     > replying
    > > >             > >             > >     >         >     > >> to this email
    > or
    > > > by telephone
    > > >             > > (+44(020 7896
    > > >             > >             > 0011)
    > > >             > >             > > and
    > > >             > >             > >     > then delete
    > > >             > >             > >     >         > the
    > > >             > >             > >     >         >     > email
    > > >             > >             > >     >         >     > >> and any copies
    > > of
    > > > it. Opinions,
    > > >             > > conclusion (etc)
    > > >             > >             > > that
    > > >             > >             > >     > do not
    > > >             > >             > >     >         > relate to
    > > >             > >             > >     >         >     > the
    > > >             > >             > >     >         >     > >> official
    > > business
    > > > of this
    > > >             > company
    > > >             > > shall be
    > > >             > >             > > understood
    > > >             > >             > >     > as neither
    > > >             > >             > >     >         > given
    > > >             > >             > >     >         >     > nor
    > > >             > >             > >     >         >     > >> endorsed by
    > it.
    > > > IG is a trading
    > > >             > > name of IG
    > > >             > >             > Markets
    > > >             > >             > >     > Limited (a
    > > >             > >             > >     >         > company
    > > >             > >             > >     >         >     > >> registered in
    > > > England and Wales,
    > > >             > > company number
    > > >             > >             > >     > 04008957) and IG
    > > >             > >             > >     >         > Index
    > > >             > >             > >     >         >     > >> Limited (a
    > > > company registered in
    > > >             > > England and
    > > >             > >             > > Wales,
    > > >             > >             > >     > company number
    > > >             > >             > >     >         >     > >> 01190902).
    > > > Registered address at
    > > >             > > Cannon Bridge
    > > >             > >             > > House,
    > > >             > >             > >     > 25 Dowgate
    > > >             > >             > >     >         > Hill,
    > > >             > >             > >     >         >     > >> London EC4R
    > 2YA.
    > > > Both IG Markets
    > > >             > > Limited
    > > >             > >             > (register
    > > >             > >             > >     > number 195355)
    > > >             > >             > >     >         > and IG
    > > >             > >             > >     >         >     > >> Index Limited
    > > > (register number
    > > >             > > 114059) are
    > > >             > >             > > authorised
    > > >             > >             > >     > and
    > > >             > >             > >     >         > regulated by
    > > >             > >             > >     >         >     > the
    > > >             > >             > >     >         >     > >> Financial
    > > Conduct
    > > > Authority.
    > > >             > >             > >     >         >     > >>
    > > >             > >             > >     >         >     > >
    > > >             > >             > >     >         >     > >
    > > >             > >             > >     >         >     >
    > > >             > >             > >     >         >     The information
    > > > contained in this
    > > >             > > email is strictly
    > > >             > >             > >     > confidential and
    > > >             > >             > >     >         > for the use of the
    > > > addressee only, unless
    > > >             > > otherwise
    > > >             > >             > > indicated.
    > > >             > >             > >     > If you are
    > > >             > >             > >     >         > not the intended
    > > > recipient, please do not
    > > >             > > read, copy, use
    > > >             > >             > > or
    > > >             > >             > >     > disclose to
    > > >             > >             > >     >         > others this message or
    > > any
    > > > attachment.
    > > >             > > Please also notify
    > > >             > >             > > the
    > > >             > >             > >     > sender by
    > > >             > >             > >     >         > replying to this email
    > or
    > > > by telephone
    > > >             > > (+44(020 7896
    > > >             > >             > 0011)
    > > >             > >             > > and
    > > >             > >             > >     > then delete
    > > >             > >             > >     >         > the email and any
    > copies
    > > > of it. Opinions,
    > > >             > > conclusion
    > > >             > >             > (etc)
    > > >             > >             > > that
    > > >             > >             > >     > do not
    > > >             > >             > >     >         > relate to the official
    > > > business of this
    > > >             > > company shall be
    > > >             > >             > >     > understood as
    > > >             > >             > >     >         > neither given nor
    > > endorsed
    > > > by it. IG is a
    > > >             > > trading name of
    > > >             > >             > > IG
    > > >             > >             > >     > Markets
    > > >             > >             > >     >         > Limited (a company
    > > > registered in England
    > > >             > > and Wales,
    > > >             > >             > company
    > > >             > >             > >     > number
    > > >             > >             > >     >         > 04008957) and IG Index
    > > > Limited (a company
    > > >             > > registered in
    > > >             > >             > > England
    > > >             > >             > >     > and Wales,
    > > >             > >             > >     >         > company number
    > 01190902).
    > > > Registered
    > > >             > > address at Cannon
    > > >             > >             > > Bridge
    > > >             > >             > >     > House, 25
    > > >             > >             > >     >         > Dowgate Hill, London
    > EC4R
    > > > 2YA. Both IG
    > > >             > > Markets Limited
    > > >             > >             > > (register
    > > >             > >             > >     > number
    > > >             > >             > >     >         > 195355) and IG Index
    > > > Limited (register
    > > >             > > number 114059) are
    > > >             > >             > >     > authorised and
    > > >             > >             > >     >         > regulated by the
    > > Financial
    > > > Conduct
    > > >             > > Authority.
    > > >             > >             > >     >         >
    > > >             > >             > >     >         >
    > > >             > >             > >     >         >
    > > >             > >             > >     >         >
    > > >             > >             > >     >
    > > >             > >             > >     >
    > > >             > >             > >     >     The information contained in
    > > > this email is
    > > >             > > strictly
    > > >             > >             > confidential
    > > >             > >             > > and
    > > >             > >             > >     > for the use of the addressee
    > only,
    > > > unless otherwise
    > > >             > > indicated. If
    > > >             > >             > > you are
    > > >             > >             > >     > not the intended recipient,
    > please
    > > > do not read,
    > > >             > > copy, use or
    > > >             > >             > > disclose to
    > > >             > >             > >     > others this message or any
    > > > attachment. Please also
    > > >             > > notify the
    > > >             > >             > sender
    > > >             > >             > > by
    > > >             > >             > >     > replying to this email or by
    > > > telephone (+44(020
    > > >             > 7896
    > > >             > > 0011) and then
    > > >             > >             > > delete
    > > >             > >             > >     > the email and any copies of it.
    > > > Opinions,
    > > >             > conclusion
    > > >             > > (etc) that do
    > > >             > >             > > not
    > > >             > >             > >     > relate to the official business
    > of
    > > > this company
    > > >             > > shall be understood
    > > >             > >             > > as
    > > >             > >             > >     > neither given nor endorsed by it.
    > > IG
    > > > is a trading
    > > >             > > name of IG
    > > >             > >             > Markets
    > > >             > >             > >     > Limited (a company registered in
    > > > England and Wales,
    > > >             > > company number
    > > >             > >             > >     > 04008957) and IG Index Limited (a
    > > > company
    > > >             > registered
    > > >             > > in England and
    > > >             > >             > > Wales,
    > > >             > >             > >     > company number 01190902).
    > > Registered
    > > > address at
    > > >             > > Cannon Bridge
    > > >             > >             > House,
    > > >             > >             > > 25
    > > >             > >             > >     > Dowgate Hill, London EC4R 2YA.
    > Both
    > > > IG Markets
    > > >             > > Limited (register
    > > >             > >             > > number
    > > >             > >             > >     > 195355) and IG Index Limited
    > > > (register number
    > > >             > > 114059) are
    > > >             > >             > authorised
    > > >             > >             > > and
    > > >             > >             > >     > regulated by the Financial
    > Conduct
    > > > Authority.
    > > >             > >             > >     >
    > > >             > >             > >     >
    > > >             > >             > >     >
    > > >             > >             > >
    > > >             > >             > >
    > > >             > >             > > The information contained in this email
    > > is
    > > > strictly
    > > >             > > confidential and for
    > > >             > >             > > the use of the addressee only, unless
    > > > otherwise
    > > >             > indicated.
    > > >             > > If you are not
    > > >             > >             > > the intended recipient, please do not
    > > > read, copy, use or
    > > >             > > disclose to
    > > >             > >             > others
    > > >             > >             > > this message or any attachment. Please
    > > > also notify the
    > > >             > > sender by replying
    > > >             > >             > > to this email or by telephone (+44(020
    > > > 7896 0011) and
    > > >             > then
    > > >             > > delete the
    > > >             > >             > email
    > > >             > >             > > and any copies of it. Opinions,
    > > conclusion
    > > > (etc) that do
    > > >             > > not relate to
    > > >             > >             > the
    > > >             > >             > > official business of this company shall
    > > be
    > > > understood as
    > > >             > > neither given
    > > >             > >             > nor
    > > >             > >             > > endorsed by it. IG is a trading name of
    > > IG
    > > > Markets
    > > >             > Limited
    > > >             > > (a company
    > > >             > >             > > registered in England and Wales,
    > company
    > > > number 04008957)
    > > >             > > and IG Index
    > > >             > >             > > Limited (a company registered in
    > England
    > > > and Wales,
    > > >             > > company number
    > > >             > >             > > 01190902). Registered address at Cannon
    > > > Bridge House, 25
    > > >             > > Dowgate Hill,
    > > >             > >             > > London EC4R 2YA. Both IG Markets
    > Limited
    > > > (register number
    > > >             > > 195355) and IG
    > > >             > >             > > Index Limited (register number 114059)
    > > are
    > > > authorised and
    > > >             > > regulated by
    > > >             > >             > the
    > > >             > >             > > Financial Conduct Authority.
    > > >             > >             > >
    > > >             > >             >
    > > >             > >
    > > >             > >
    > > >             > >
    > > >             > >
    > > >             > >     The information contained in this email is strictly
    > > > confidential and
    > > >             > > for the use of the addressee only, unless otherwise
    > > > indicated. If you are
    > > >             > > not the intended recipient, please do not read, copy,
    > use
    > > > or disclose to
    > > >             > > others this message or any attachment. Please also
    > notify
    > > > the sender by
    > > >             > > replying to this email or by telephone (+44(020 7896
    > > 0011)
    > > > and then
    > > >             > delete
    > > >             > > the email and any copies of it. Opinions, conclusion
    > > (etc)
    > > > that do not
    > > >             > > relate to the official business of this company shall
    > be
    > > > understood as
    > > >             > > neither given nor endorsed by it. IG is a trading name
    > of
    > > > IG Markets
    > > >             > > Limited (a company registered in England and Wales,
    > > > company number
    > > >             > > 04008957) and IG Index Limited (a company registered in
    > > > England and
    > > >             > Wales,
    > > >             > > company number 01190902). Registered address at Cannon
    > > > Bridge House, 25
    > > >             > > Dowgate Hill, London EC4R 2YA. Both IG Markets Limited
    > > > (register number
    > > >             > > 195355) and IG Index Limited (register number 114059)
    > are
    > > > authorised and
    > > >             > > regulated by the Financial Conduct Authority.
    > > >             > >
    > > >             > >
    > > >             > >
    > > >             >
    > > >
    > > >
    > > >
    > > >
    > > >
    > > >
    > > > The information contained in this email is strictly confidential and
    > for
    > > > the use of the addressee only, unless otherwise indicated. If you are
    > not
    > > > the intended recipient, please do not read, copy, use or disclose to
    > > others
    > > > this message or any attachment. Please also notify the sender by
    > replying
    > > > to this email or by telephone (+44(020 7896 0011) and then delete the
    > > email
    > > > and any copies of it. Opinions, conclusion (etc) that do not relate to
    > > the
    > > > official business of this company shall be understood as neither given
    > > nor
    > > > endorsed by it. IG is a trading name of IG Markets Limited (a company
    > > > registered in England and Wales, company number 04008957) and IG Index
    > > > Limited (a company registered in England and Wales, company number
    > > > 01190902). Registered address at Cannon Bridge House, 25 Dowgate Hill,
    > > > London EC4R 2YA. Both IG Markets Limited (register number 195355) and
    > IG
    > > > Index Limited (register number 114059) are authorised and regulated by
    > > the
    > > > Financial Conduct Authority.
    > > >
    > >
    >


The information contained in this email is strictly confidential and for the use of the addressee only, unless otherwise indicated. If you are not the intended recipient, please do not read, copy, use or disclose to others this message or any attachment. Please also notify the sender by replying to this email or by telephone (+44(020 7896 0011) and then delete the email and any copies of it. Opinions, conclusion (etc) that do not relate to the official business of this company shall be understood as neither given nor endorsed by it. IG is a trading name of IG Markets Limited (a company registered in England and Wales, company number 04008957) and IG Index Limited (a company registered in England and Wales, company number 01190902). Registered address at Cannon Bridge House, 25 Dowgate Hill, London EC4R 2YA. Both IG Markets Limited (register number 195355) and IG Index Limited (register number 114059) are authorised and regulated by the Financial Conduct Authority.
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