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From Michael Pearce <Michael.Pea...@ig.com>
Subject Re: [DISCUSS] KIP-87 - Add Compaction Tombstone Flag
Date Mon, 07 Nov 2016 17:59:03 GMT
Hi Becket,

We were thinking more about having the logic that’s in the method shouldRetainMessage configurable
via http://kafka.apache.org/documentation.html#brokerconfigs  at a broker/topic level. And
then scrap auto converting the message, and allow organisations to manage the rollout of enabling
of the feature.
(this isn’t in documentation but in response to the discussion thread as an alternative
approach to roll out the feature)

Does this make any more sense?

Thanks
Mike

On 11/3/16, 2:27 PM, "Becket Qin" <becket.qin@gmail.com> wrote:

    Hi Michael,

    Do you mean using a new configuration it is just the exiting
    message.format.version config? It seems the message.format.version config
    is enough in this case. And the default value would always be the latest
    version.

    > Message version migration would be handled as like in KIP-32

    Also just want to confirm on this. Today if an old consumer consumes a log
    compacted topic and sees an empty value, it knows that is a tombstone.
    After we start to use the attribute bit, a tombstone message can have a
    non-empty value. So by "like in KIP-32" you mean we will remove the value
    to down convert the message if the consumer version is old, right?

    Thanks.

    Jiangjie (Becket) Qin

    On Wed, Nov 2, 2016 at 1:37 AM, Michael Pearce <Michael.Pearce@ig.com>
    wrote:

    > Hi Joel , et al.
    >
    > Any comments on the below idea to handle roll out / compatibility of this
    > feature, using a configuration?
    >
    > Does it make sense/clear?
    > Does it add value?
    > Do we want to enforce flag by default, or value by default, or both?
    >
    > Cheers
    > Mike
    >
    >
    > On 10/27/16, 4:47 PM, "Michael Pearce" <Michael.Pearce@ig.com> wrote:
    >
    >     Thanks, James, I think this is a really good addition to the KIP
    > details, please feel free to amend the wiki/add the use cases, also if any
    > others you think of. I definitely think its worthwhile documenting. If you
    > can’t let me know ill add them next week (just leaving for a long weekend
    > off)
    >
    >     Re Joel and others comments about upgrade and compatibility.
    >
    >     Rather than trying to auto manage this.
    >
    >     Actually maybe we make a configuration option, both at server and per
    > topic level to control the behavior of how the server logic should work out
    > if the record, is a tombstone record .
    >
    >     e.g.
    >
    >     key = compation.tombstone.marker
    >
    >     value options:
    >
    >     value   (continues to use null value as tombstone marker)
    >     flag (expects to use the tombstone flag)
    >     value_or_flag (if either is true it treats the record as a tombstone)
    >
    >     This way on upgrade users can keep current behavior, and slowly
    > migrate to the new. Having a transition period of using value_or_flag,
    > finally having flag only if an organization wishes to use null values
    > without it being treated as a tombstone marker (use case noted below)
    >
    >     Having it both global broker level and topic override also allows some
    > flexibility here.
    >
    >     Cheers
    >     Mike
    >
    >
    >
    >
    >
    >
    >     On 10/27/16, 8:03 AM, "James Cheng" <wushujames@gmail.com> wrote:
    >
    >         This KIP would definitely address a gap in the current
    > functionality, where you currently can't have a tombstone with any
    > associated content.
    >
    >         That said, I'd like to talk about use cases, to make sure that
    > this is in fact useful. The KIP should be updated with whatever use cases
    > we come up with.
    >
    >         First of all, an observation: When we speak about log compaction,
    > we typically think of "the latest message for a key is retained". In that
    > respect, a delete tombstone (i.e. a message with a null payload) is treated
    > the same as any other Kafka message: the latest message is retained. It
    > doesn't matter whether the latest message is null, or if the latest message
    > has actual content. In all cases, the last message is retained.
    >
    >         The only way a delete tombstone is treated differently from other
    > Kafka messages is that it automatically disappears after a while. The time
    > of deletion is specified using delete.retention.ms.
    >
    >         So what we're really talking about is, do we want to support
    > messages in a log-compacted topic that auto-delete themselves after a while?
    >
    >         In a thread from 2015, there was a discussion on first-class
    > support of headers between Roger Hoover, Felix GV, Jun Rao, and I. See
    > thread at https://groups.google.com/d/msg/confluent-platform/
    > 8xPbjyUE_7E/yQ1AeCufL_gJ <https://groups.google.com/d/
    > msg/confluent-platform/8xPbjyUE_7E/yQ1AeCufL_gJ> . In that thread, Jun
    > raised a good question that I didn't have a good answer for at the time: If
    > a message is going to auto-delete itself after a while, how important was
    > the message? That is, what information did the message contain that was
    > important *for a while* but not so important that it needed to be kept
    > around forever?
    >
    >         Some use cases that I can think of:
    >
    >         1) Tracability. I would like to know who issued this delete
    > tombstone. It might include the hostname, IP of the producer of the delete.
    >         2) Timestamps. I would like to know when this delete was issued.
    > This use case is already addressed by the availability of per-message
    > timestamps that came in 0.10.0
    >         3) Data provenance. I hope I'm using this phrase correctly, but
    > what I mean is, where did this delete come from? What processing job
    > emitted it? What input to the processing job caused this delete to be
    > produced? For example, if a record in topic A was processed and caused a
    > delete tombstone to be emitted to topic B, I might like the offset of the
    > topic A message to be attached to the topic B message.
    >         4) Distributed tracing for stream topologies. This might be a
    > slight repeat of the above use cases. In the microservices world, we can
    > generate call-graphs of webservices using tools like Zipkin/opentracing.io
    > <http://opentracing.io/>, or something homegrown like
    > https://engineering.linkedin.com/distributed-service-call-
    > graph/real-time-distributed-tracing-website-performance-and-efficiency <
    > https://engineering.linkedin.com/distributed-service-call-
    > graph/real-time-distributed-tracing-website-performance-and-efficiency>.
    > I can imagine that you might want to do something similar for stream
    > processing topologies, where stream processing jobs carry along and forward
    > along a globally unique identifier, and a distributed topology graph is
    > generated.
    >         5) Cases where processing a delete requires data that is not
    > available in the message key. I'm not sure I have a good example of this,
    > though. One hand-wavy example might be where I am publishing documents into
    > Kafka where the documentId is the message key, and the text contents of the
    > document are in the message body. And I have a consuming job that does some
    > analytics on the message body. If that document gets deleted, then the
    > consuming job might need the original message body in order to "delete"
    > that message's impact from the analytics. But I'm not sure that is a great
    > example. If the consumer was worried about that, the consumer would
    > probably keep the original message around, stored by primary key. And then
    > all it would need from a delete message would be the primary key of the
    > message.
    >
    >         Do people think these are valid use cases?
    >
    >         What are other use cases that people can think of?
    >
    >         -James
    >
    >         > On Oct 26, 2016, at 3:46 PM, Mayuresh Gharat <
    > gharatmayuresh15@gmail.com> wrote:
    >         >
    >         > +1 @Joel.
    >         > I think a clear migration plan of upgrading and downgrading of
    > server and
    >         > clients along with handling of issues that Joel mentioned, on
    > the KIP would
    >         > be really great.
    >         >
    >         > Thanks,
    >         >
    >         > Mayuresh
    >         >
    >         > On Wed, Oct 26, 2016 at 3:31 PM, Joel Koshy <jjkoshy.w@gmail.com>
    > wrote:
    >         >
    >         >> I'm not sure why it would be useful, but it should be
    > theoretically
    >         >> possible if the attribute bit alone is enough to mark a
    > tombstone. OTOH, we
    >         >> could consider that as invalid if we wish. These are relevant
    > details that
    >         >> I think should be added to the KIP.
    >         >>
    >         >> Also, in the few odd scenarios that I mentioned we should also
    > consider
    >         >> that fetches could be coming from other yet-to-be-upgraded
    > brokers in a
    >         >> cluster that is being upgraded. So we would probably want to
    > continue to
    >         >> support nulls as tombstones or down-convert in a way that we
    > are sure works
    >         >> with least surprise to fetchers.
    >         >>
    >         >> There is a slightly vague statement under "Compatibility,
    > Deprecation, and
    >         >> Migration Plan" that could benefit more details: *Logic would
    > base on
    >         >> current behavior of null value or if tombstone flag set to
    > true, as such
    >         >> wouldn't impact any existing flows simply allow new producers
    > to make use
    >         >> of the feature*. It is unclear to me based on that whether you
    > would
    >         >> interpret null as a tombstone if the tombstone attribute bit is
    > off.
    >         >>
    >         >> On Wed, Oct 26, 2016 at 3:10 PM, Xavier Léauté <
    > xavier@confluent.io>
    >         >> wrote:
    >         >>
    >         >>> Does this mean that starting with V4 requests we would allow
    > storing null
    >         >>> messages in compacted topics? The KIP should probably clarify
    > the
    >         >> behavior
    >         >>> for null messages where the tombstone flag is not net.
    >         >>>
    >         >>> On Wed, Oct 26, 2016 at 1:32 AM Magnus Edenhill <
    > magnus@edenhill.se>
    >         >>> wrote:
    >         >>>
    >         >>>> 2016-10-25 21:36 GMT+02:00 Nacho Solis
    > <nsolis@linkedin.com.invalid>:
    >         >>>>
    >         >>>>> I think you probably require a MagicByte bump if you
expect
    > correct
    >         >>>>> behavior of the system as a whole.
    >         >>>>>
    >         >>>>> From a client perspective you want to make sure that
when you
    >         >> deliver a
    >         >>>>> message that the broker supports the feature you're
expecting
    >         >>>>> (compaction).  So, depending on the behavior of the
broker on
    >         >>>> encountering
    >         >>>>> a previously undefined bit flag I would suggest making
some
    > change to
    >         >>>> make
    >         >>>>> certain that flag-based compaction is supported.  I'm
going
    > to guess
    >         >>> that
    >         >>>>> the MagicByte would do this.
    >         >>>>>
    >         >>>>
    >         >>>> I dont believe this is needed since it is already attributed
    > through
    >         >> the
    >         >>>> request's API version.
    >         >>>>
    >         >>>> Producer:
    >         >>>> * if a client sends ProduceRequest V4 then attributes.bit5
    > indicates a
    >         >>>> tombstone
    >         >>>> * if a clients sends ProduceRequest <V4 then attributes.bit5
    > is
    >         >> ignored
    >         >>>> and value==null indicates a tombstone
    >         >>>> * in both cases the on-disk messages are stored with
    > attributes.bit5
    >         >> (I
    >         >>>> assume?)
    >         >>>>
    >         >>>> Consumer:
    >         >>>> * if a clients sends FetchRequest V4 messages are
    > sendfile():ed
    >         >> directly
    >         >>>> from disk (with attributes.bit5)
    >         >>>> * if a client sends FetchRequest <V4 messages are slowpathed
    > and
    >         >>>> translated from attributes.bit5 to value=null as required.
    >         >>>>
    >         >>>>
    >         >>>> That's my understanding anyway, please correct me if I'm
    > wrong.
    >         >>>>
    >         >>>> /Magnus
    >         >>>>
    >         >>>>
    >         >>>>
    >         >>>>> On Tue, Oct 25, 2016 at 10:17 AM, Magnus Edenhill <
    >         >> magnus@edenhill.se>
    >         >>>>> wrote:
    >         >>>>>
    >         >>>>>> It is safe to assume that a previously undefined
attributes
    > bit
    >         >> will
    >         >>> be
    >         >>>>>> unset in protocol requests from existing clients,
if not,
    > such a
    >         >>> client
    >         >>>>> is
    >         >>>>>> already violating the protocol and needs to be fixed.
    >         >>>>>>
    >         >>>>>> So I dont see a need for a MagicByte bump, both
broker and
    > client
    >         >> has
    >         >>>> the
    >         >>>>>> information it needs to construct or parse the message
    > according to
    >         >>>>> request
    >         >>>>>> version.
    >         >>>>>>
    >         >>>>>>
    >         >>>>>> 2016-10-25 18:48 GMT+02:00 Michael Pearce <
    > Michael.Pearce@ig.com>:
    >         >>>>>>
    >         >>>>>>> Hi Magnus,
    >         >>>>>>>
    >         >>>>>>> I was wondering if I even needed to change those
also, as
    >         >>> technically
    >         >>>>>>> we’re just making use of a non used attribute
bit, but im
    > not
    >         >> 100%
    >         >>>> that
    >         >>>>>> it
    >         >>>>>>> be always false currently.
    >         >>>>>>>
    >         >>>>>>> If someone can say 100% it will already be set
false with
    > current
    >         >>> and
    >         >>>>>>> historic bit wise masking techniques used over
the time,
    > we could
    >         >>> do
    >         >>>>> away
    >         >>>>>>> with both, and simply just start to use it.
Unfortunately
    > I don’t
    >         >>>> have
    >         >>>>>> that
    >         >>>>>>> historic knowledge so was hoping it would be
flagged up in
    > this
    >         >>>>>> discussion
    >         >>>>>>> thread ☺
    >         >>>>>>>
    >         >>>>>>> Cheers
    >         >>>>>>> Mike
    >         >>>>>>>
    >         >>>>>>> On 10/25/16, 5:36 PM, "Magnus Edenhill" <
    > magnus@edenhill.se>
    >         >>> wrote:
    >         >>>>>>>
    >         >>>>>>>    Hi Michael,
    >         >>>>>>>
    >         >>>>>>>    With the version bumps for Produce and Fetch
requests,
    > do you
    >         >>>>> really
    >         >>>>>>> need
    >         >>>>>>>    to bump MagicByte too?
    >         >>>>>>>
    >         >>>>>>>    Regards,
    >         >>>>>>>    Magnus
    >         >>>>>>>
    >         >>>>>>>
    >         >>>>>>>    2016-10-25 18:09 GMT+02:00 Michael Pearce
<
    >         >>> Michael.Pearce@ig.com
    >         >>>>> :
    >         >>>>>>>
    >         >>>>>>>> Hi All,
    >         >>>>>>>>
    >         >>>>>>>> I would like to discuss the following KIP
proposal:
    >         >>>>>>>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-
    >         >>>>>>>> 87+-+Add+Compaction+Tombstone+Flag
    >         >>>>>>>>
    >         >>>>>>>> This is off the back of the discussion on
KIP-82  / KIP
    >         >>> meeting
    >         >>>>>>> where it
    >         >>>>>>>> was agreed to separate this issue and feature.
See:
    >         >>>>>>>> http://mail-archives.apache.org/mod_mbox/kafka-dev/201610
    > .
    >         >>>>>>>> mbox/%3cCAJS3ho8OcR==EcxsJ8OP99pD2hz=iiGecWsv-
    >         >>>>>>>> EZsBsNyDcKr=g@mail.gmail.com%3e
    >         >>>>>>>>
    >         >>>>>>>> Thanks
    >         >>>>>>>> Mike
    >         >>>>>>>>
    >         >>>>>>>> The information contained in this email
is strictly
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    >         >>>>>>> to the
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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
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    >         >>>>>>> this message or any attachment. Please also
notify the
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0011) and then
    > delete
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    >         >>>>>>> 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
    >         >>>>> Kafka
    >         >>>>> nsolis@linkedin.com
    >         >>>>>
    >         >>>>
    >         >>>
    >         >>
    >         >
    >         >
    >         >
    >         > --
    >         > -Regards,
    >         > Mayuresh R. Gharat
    >         > (862) 250-7125
    >
    >
    >
    >     The information contained in this email is strictly confidential and
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    > 04008957) and IG Index Limited (a company registered in England and Wales,
    > company number 01190902). Registered address at Cannon Bridge House, 25
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    > 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
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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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