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From Rajini Sivaram <rajinisiva...@gmail.com>
Subject Re: [DISCUSS] KIP-124: Request rate quotas
Date Tue, 07 Mar 2017 19:04:24 GMT
Jun,

Thank you for the explanation, I hadn't realized you meant percentage of
the total thread pool. If everyone is OK with Jun's suggestion, I will
update the KIP.

Thanks,

Rajini

On Tue, Mar 7, 2017 at 5:08 PM, Jun Rao <jun@confluent.io> wrote:

> Hi, Rajini,
>
> Let's take your example. Let's say a user sets the limit to 50%. I am not
> sure if it's better to apply the same percentage separately to network and
> io thread pool. For example, for produce requests, most of the time will be
> spent in the io threads whereas for fetch requests, most of the time will
> be in the network threads. So, using the same percentage in both thread
> pools means one of the pools' resource will be over allocated.
>
> An alternative way is to simply model network and io thread pool together.
> If you get 10 io threads and 5 network threads, you get 1500% request
> processing power. A 50% limit means a total of 750% processing power. We
> just add up the time a user request spent in either network or io thread.
> If that total exceeds 750% (doesn't matter whether it's spent more in
> network or io thread), the request will be throttled. This seems more
> general and is not sensitive to the current implementation detail of having
> a separate network and io thread pool. In the future, if the threading
> model changes, the same concept of quota can still be applied. For now,
> since it's a bit tricky to add the delay logic in the network thread pool,
> we could probably just do the delaying only in the io threads as you
> suggested earlier.
>
> There is still the orthogonal question of whether a quota of 50% is out of
> 100% or 100% * #total processing threads. My feeling is that the latter is
> slightly better based on my explanation earlier. The way to describe this
> quota to the users can be "share of elapsed request processing time on a
> single CPU" (similar to top).
>
> Thanks,
>
> Jun
>
>
> On Fri, Mar 3, 2017 at 4:22 AM, Rajini Sivaram <rajinisivaram@gmail.com>
> wrote:
>
> > Jun,
> >
> > Agree about the two scenarios.
> >
> > But still not sure about a single quota covering both network threads and
> > I/O threads with per-thread quota. If there are 10 I/O threads and 5
> > network threads and I want to assign half the quota to userA, the quota
> > would be 750%. I imagine, internally, we would convert this to 500% for
> I/O
> > and 250% for network threads to allocate 50% of each pool.
> >
> > A couple of scenarios:
> >
> > 1. Admin adds 1 extra network thread. To retain 50%, admin needs to now
> > allocate 800% for each user. Or increase the quota for a few users. To
> me,
> > it feels like admin needs to convert 50% to 800% and Kafka internally
> needs
> > to convert 800% to (500%, 300%). Everyone using just 50% feels a lot
> > simpler.
> >
> > 2. We decide to add some other thread to this list. Admin needs to know
> > exactly how many threads form the maximum quota. And we can be changing
> > this between broker versions as we add more to the list. Again a single
> > overall percent would be a lot simpler.
> >
> > There were others who were unconvinced by a single percent from the
> initial
> > proposal and were happier with thread units similar to CPU units, so I am
> > ok with going with per-thread quotas (as units or percent). Just not sure
> > it makes it easier for admin in all cases.
> >
> > Regards,
> >
> > Rajini
> >
> >
> > On Fri, Mar 3, 2017 at 6:03 AM, Jun Rao <jun@confluent.io> wrote:
> >
> > > Hi, Rajini,
> > >
> > > Consider modeling as n * 100% unit. For 2), the question is what's
> > causing
> > > the I/O threads to be saturated. It's unlikely that all users'
> > utilization
> > > have increased at the same. A more likely case is that a few isolated
> > > users' utilization have increased. If so, after increasing the number
> of
> > > threads, the admin just needs to adjust the quota for a few isolated
> > users,
> > > which is expected and is less work.
> > >
> > > Consider modeling as 1 * 100% unit. For 1), all users' quota need to be
> > > adjusted, which is unexpected and is more work.
> > >
> > > So, to me, the n * 100% model seems more convenient.
> > >
> > > As for future extension to cover network thread utilization, I was
> > thinking
> > > that one way is to simply model the capacity as (n + m) * 100% unit,
> > where
> > > n and m are the number of network and i/o threads, respectively. Then,
> > for
> > > each user, we can just add up the utilization in the network and the
> i/o
> > > thread. If we do this, we don't need a new type of quota.
> > >
> > > Thanks,
> > >
> > > Jun
> > >
> > >
> > > On Thu, Mar 2, 2017 at 12:27 PM, Rajini Sivaram <
> rajinisivaram@gmail.com
> > >
> > > wrote:
> > >
> > > > Jun,
> > > >
> > > > If we use request.percentage as the percentage used in a single I/O
> > > thread,
> > > > the total percentage being allocated will be num.io.threads * 100 for
> > I/O
> > > > threads and num.network.threads * 100 for network threads. A single
> > quota
> > > > covering the two as a percentage wouldn't quite work if you want to
> > > > allocate the same proportion in both cases. If we want to treat
> threads
> > > as
> > > > separate units, won't we need two quota configurations regardless of
> > > > whether we use units or percentage? Perhaps I misunderstood your
> > > > suggestion.
> > > >
> > > > I think there are two cases:
> > > >
> > > >    1. The use case that you mentioned where an admin is adding more
> > users
> > > >    and decides to add more I/O threads and expects to find free quota
> > to
> > > >    allocate for new users.
> > > >    2. Admin adds more I/O threads because the I/O threads are
> saturated
> > > and
> > > >    there are cores available to allocate, even though the number or
> > > >    users/clients hasn't changed.
> > > >
> > > > If we allocated treated I/O threads as a single unit of 100%, all
> user
> > > > quotas need to be reallocated for 1). If we allocated I/O threads as
> n
> > > > units with n*100%, all user quotas need to be reallocated for 2),
> > > otherwise
> > > > some of the new threads may just not be used. Either way it should be
> > > easy
> > > > to write a script to decrease/increase quotas by a multiple for all
> > > users.
> > > >
> > > > So it really boils down to which quota unit is most intuitive in
> terms
> > of
> > > > configuration. And from the discussion so far, it feels like opinion
> is
> > > > divided on whether quotas should be carved out of an absolute 100%
> (or
> > 1
> > > > unit) or be relative to the number of threads (n*100% or n units).
> > > >
> > > >
> > > >
> > > > On Thu, Mar 2, 2017 at 7:31 PM, Jun Rao <jun@confluent.io> wrote:
> > > >
> > > > > Another way to express an absolute limit is to use
> > request.percentage,
> > > > but
> > > > > treat it as the percentage used in a single request handling
> thread.
> > > For
> > > > > now, the request handling threads can be just the io threads. In
> the
> > > > > future, they can cover the network threads as well. This is similar
> > to
> > > > how
> > > > > top reports CPU usage and may be a bit easier for people to
> > understand.
> > > > >
> > > > > Thanks,
> > > > >
> > > > > Jun
> > > > >
> > > > > On Fri, Feb 24, 2017 at 10:31 AM, Jun Rao <jun@confluent.io>
> wrote:
> > > > >
> > > > > > Hi, Jay,
> > > > > >
> > > > > > 2. Regarding request.unit vs request.percentage. I started with
> > > > > > request.percentage too. The reasoning for request.unit is the
> > > > following.
> > > > > > Suppose that the capacity has been reached on a broker and the
> > admin
> > > > > needs
> > > > > > to add a new user. A simple way to increase the capacity is to
> > > increase
> > > > > the
> > > > > > number of io threads, assuming there are still enough cores. If
> the
> > > > limit
> > > > > > is based on percentage, the additional capacity automatically
> gets
> > > > > > distributed to existing users and we haven't really carved out
> any
> > > > > > additional resource for the new user. Now, is it easy for a user
> to
> > > > > reason
> > > > > > about 0.1 unit vs 10%. My feeling is that both are hard and have
> to
> > > be
> > > > > > configured empirically. Not sure if percentage is obviously
> easier
> > to
> > > > > > reason about.
> > > > > >
> > > > > > Thanks,
> > > > > >
> > > > > > Jun
> > > > > >
> > > > > > On Fri, Feb 24, 2017 at 8:10 AM, Jay Kreps <jay@confluent.io>
> > wrote:
> > > > > >
> > > > > >> A couple of quick points:
> > > > > >>
> > > > > >> 1. Even though the implementation of this quota is only using io
> > > > thread
> > > > > >> time, i think we should call it something like "request-time".
> > This
> > > > will
> > > > > >> give us flexibility to improve the implementation to cover
> network
> > > > > threads
> > > > > >> in the future and will avoid exposing internal details like our
> > > thread
> > > > > >> pools on the server.
> > > > > >>
> > > > > >> 2. Jun/Roger, I get what you are trying to fix but the idea of
> > > > > >> thread/units
> > > > > >> is super unintuitive as a user-facing knob. I had to read the
> KIP
> > > like
> > > > > >> eight times to understand this. I'm not sure that your point
> that
> > > > > >> increasing the number of threads is a problem with a
> > > percentage-based
> > > > > >> value, it really depends on whether the user thinks about the
> > > > > "percentage
> > > > > >> of request processing time" or "thread units". If they think "I
> > have
> > > > > >> allocated 10% of my request processing time to user x" then it
> is
> > a
> > > > bug
> > > > > >> that increasing the thread count decreases that percent as it
> does
> > > in
> > > > > the
> > > > > >> current proposal. As a practical matter I think the only way to
> > > > actually
> > > > > >> reason about this is as a percent---I just don't believe people
> > are
> > > > > going
> > > > > >> to think, "ah, 4.3 thread units, that is the right amount!".
> > > Instead I
> > > > > >> think they have to understand this thread unit concept, figure
> out
> > > > what
> > > > > >> they have set in number of threads, compute a percent and then
> > come
> > > up
> > > > > >> with
> > > > > >> the number of thread units, and these will all be wrong if that
> > > thread
> > > > > >> count changes. I also think this ties us to throttling the I/O
> > > thread
> > > > > >> pool,
> > > > > >> which may not be where we want to end up.
> > > > > >>
> > > > > >> 3. For what it's worth I do think having a single throttle_ms
> > field
> > > in
> > > > > all
> > > > > >> the responses that combines all throttling from all quotas is
> > > probably
> > > > > the
> > > > > >> simplest. There could be a use case for having separate fields
> for
> > > > each,
> > > > > >> but I think that is actually harder to use/monitor in the common
> > > case
> > > > so
> > > > > >> unless someone has a use case I think just one should be fine.
> > > > > >>
> > > > > >> -Jay
> > > > > >>
> > > > > >> On Fri, Feb 24, 2017 at 4:21 AM, Rajini Sivaram <
> > > > > rajinisivaram@gmail.com>
> > > > > >> wrote:
> > > > > >>
> > > > > >> > I have updated the KIP based on the discussions so far.
> > > > > >> >
> > > > > >> >
> > > > > >> > Regards,
> > > > > >> >
> > > > > >> > Rajini
> > > > > >> >
> > > > > >> > On Thu, Feb 23, 2017 at 11:29 PM, Rajini Sivaram <
> > > > > >> rajinisivaram@gmail.com>
> > > > > >> > wrote:
> > > > > >> >
> > > > > >> > > Thank you all for the feedback.
> > > > > >> > >
> > > > > >> > > Ismael #1. It makes sense not to throttle inter-broker
> > requests
> > > > like
> > > > > >> > > LeaderAndIsr etc. The simplest way to ensure that clients
> > cannot
> > > > use
> > > > > >> > these
> > > > > >> > > requests to bypass quotas for DoS attacks is to ensure that
> > ACLs
> > > > > >> prevent
> > > > > >> > > clients from using these requests and unauthorized requests
> > are
> > > > > >> included
> > > > > >> > > towards quotas.
> > > > > >> > >
> > > > > >> > > Ismael #2, Jay #1 : I was thinking that these quotas can
> > return
> > > a
> > > > > >> > separate
> > > > > >> > > throttle time, and all utilization based quotas could use
> the
> > > same
> > > > > >> field
> > > > > >> > > (we won't add another one for network thread utilization for
> > > > > >> instance).
> > > > > >> > But
> > > > > >> > > perhaps it makes sense to keep byte rate quotas separate in
> > > > > >> produce/fetch
> > > > > >> > > responses to provide separate metrics? Agree with Ismael
> that
> > > the
> > > > > >> name of
> > > > > >> > > the existing field should be changed if we have two. Happy
> to
> > > > switch
> > > > > >> to a
> > > > > >> > > single combined throttle time if that is sufficient.
> > > > > >> > >
> > > > > >> > > Ismael #4, #5, #6: Will update KIP. Will use dot separated
> > name
> > > > for
> > > > > >> new
> > > > > >> > > property. Replication quotas use dot separated, so it will
> be
> > > > > >> consistent
> > > > > >> > > with all properties except byte rate quotas.
> > > > > >> > >
> > > > > >> > > Radai: #1 Request processing time rather than request rate
> > were
> > > > > chosen
> > > > > >> > > because the time per request can vary significantly between
> > > > requests
> > > > > >> as
> > > > > >> > > mentioned in the discussion and KIP.
> > > > > >> > > #2 Two separate quotas for heartbeats/regular requests feel
> > like
> > > > > more
> > > > > >> > > configuration and more metrics. Since most users would set
> > > quotas
> > > > > >> higher
> > > > > >> > > than the expected usage and quotas are more of a safety
> net, a
> > > > > single
> > > > > >> > quota
> > > > > >> > > should work in most cases.
> > > > > >> > >  #3 The number of requests in purgatory is limited by the
> > number
> > > > of
> > > > > >> > active
> > > > > >> > > connections since only one request per connection will be
> > > > throttled
> > > > > >> at a
> > > > > >> > > time.
> > > > > >> > > #4 As with byte rate quotas, to use the full allocated
> quotas,
> > > > > >> > > clients/users would need to use partitions that are
> > distributed
> > > > > across
> > > > > >> > the
> > > > > >> > > cluster. The alternative of using cluster-wide quotas
> instead
> > of
> > > > > >> > per-broker
> > > > > >> > > quotas would be far too complex to implement.
> > > > > >> > >
> > > > > >> > > Dong : We currently have two ClientQuotaManagers for quota
> > types
> > > > > Fetch
> > > > > >> > and
> > > > > >> > > Produce. A new one will be added for IOThread, which manages
> > > > quotas
> > > > > >> for
> > > > > >> > I/O
> > > > > >> > > thread utilization. This will not update the Fetch or
> Produce
> > > > > >> queue-size,
> > > > > >> > > but will have a separate metric for the queue-size.  I
> wasn't
> > > > > >> planning to
> > > > > >> > > add any additional metrics apart from the equivalent ones
> for
> > > > > existing
> > > > > >> > > quotas as part of this KIP. Ratio of byte-rate to I/O thread
> > > > > >> utilization
> > > > > >> > > could be slightly misleading since it depends on the
> sequence
> > of
> > > > > >> > requests.
> > > > > >> > > But we can look into more metrics after the KIP is
> implemented
> > > if
> > > > > >> > required.
> > > > > >> > >
> > > > > >> > > I think we need to limit the maximum delay since all
> requests
> > > are
> > > > > >> > > throttled. If a client has a quota of 0.001 units and a
> single
> > > > > request
> > > > > >> > used
> > > > > >> > > 50ms, we don't want to delay all requests from the client by
> > 50
> > > > > >> seconds,
> > > > > >> > > throwing the client out of all its consumer groups. The
> issue
> > is
> > > > > only
> > > > > >> if
> > > > > >> > a
> > > > > >> > > user is allocated a quota that is insufficient to process
> one
> > > > large
> > > > > >> > > request. The expectation is that the units allocated per
> user
> > > will
> > > > > be
> > > > > >> > much
> > > > > >> > > higher than the time taken to process one request and the
> > limit
> > > > > should
> > > > > >> > > seldom be applied. Agree this needs proper documentation.
> > > > > >> > >
> > > > > >> > > Regards,
> > > > > >> > >
> > > > > >> > > Rajini
> > > > > >> > >
> > > > > >> > >
> > > > > >> > > On Thu, Feb 23, 2017 at 8:04 PM, radai <
> > > > radai.rosenblatt@gmail.com>
> > > > > >> > wrote:
> > > > > >> > >
> > > > > >> > >> @jun: i wasnt concerned about tying up a request processing
> > > > thread,
> > > > > >> but
> > > > > >> > >> IIUC the code does still read the entire request out, which
> > > might
> > > > > >> add-up
> > > > > >> > >> to
> > > > > >> > >> a non-negligible amount of memory.
> > > > > >> > >>
> > > > > >> > >> On Thu, Feb 23, 2017 at 11:55 AM, Dong Lin <
> > > lindong28@gmail.com>
> > > > > >> wrote:
> > > > > >> > >>
> > > > > >> > >> > Hey Rajini,
> > > > > >> > >> >
> > > > > >> > >> > The current KIP says that the maximum delay will be
> reduced
> > > to
> > > > > >> window
> > > > > >> > >> size
> > > > > >> > >> > if it is larger than the window size. I have a concern
> with
> > > > this:
> > > > > >> > >> >
> > > > > >> > >> > 1) This essentially means that the user is allowed to
> > exceed
> > > > > their
> > > > > >> > quota
> > > > > >> > >> > over a long period of time. Can you provide an upper
> bound
> > on
> > > > > this
> > > > > >> > >> > deviation?
> > > > > >> > >> >
> > > > > >> > >> > 2) What is the motivation for cap the maximum delay by
> the
> > > > window
> > > > > >> > size?
> > > > > >> > >> I
> > > > > >> > >> > am wondering if there is better alternative to address
> the
> > > > > problem.
> > > > > >> > >> >
> > > > > >> > >> > 3) It means that the existing metric-related config will
> > > have a
> > > > > >> more
> > > > > >> > >> > directly impact on the mechanism of this
> > io-thread-unit-based
> > > > > >> quota.
> > > > > >> > The
> > > > > >> > >> > may be an important change depending on the answer to 1)
> > > above.
> > > > > We
> > > > > >> > >> probably
> > > > > >> > >> > need to document this more explicitly.
> > > > > >> > >> >
> > > > > >> > >> > Dong
> > > > > >> > >> >
> > > > > >> > >> >
> > > > > >> > >> > On Thu, Feb 23, 2017 at 10:56 AM, Dong Lin <
> > > > lindong28@gmail.com>
> > > > > >> > wrote:
> > > > > >> > >> >
> > > > > >> > >> > > Hey Jun,
> > > > > >> > >> > >
> > > > > >> > >> > > Yeah you are right. I thought it wasn't because at
> > LinkedIn
> > > > it
> > > > > >> will
> > > > > >> > be
> > > > > >> > >> > too
> > > > > >> > >> > > much pressure on inGraph to expose those per-clientId
> > > metrics
> > > > > so
> > > > > >> we
> > > > > >> > >> ended
> > > > > >> > >> > > up printing them periodically to local log. Never mind
> if
> > > it
> > > > is
> > > > > >> not
> > > > > >> > a
> > > > > >> > >> > > general problem.
> > > > > >> > >> > >
> > > > > >> > >> > > Hey Rajini,
> > > > > >> > >> > >
> > > > > >> > >> > > - I agree with Jay that we probably don't want to add a
> > new
> > > > > field
> > > > > >> > for
> > > > > >> > >> > > every quota ProduceResponse or FetchResponse. Is there
> > any
> > > > > >> use-case
> > > > > >> > >> for
> > > > > >> > >> > > having separate throttle-time fields for
> byte-rate-quota
> > > and
> > > > > >> > >> > > io-thread-unit-quota? You probably need to document
> this
> > as
> > > > > >> > interface
> > > > > >> > >> > > change if you plan to add new field in any request.
> > > > > >> > >> > >
> > > > > >> > >> > > - I don't think IOThread belongs to quotaType. The
> > existing
> > > > > quota
> > > > > >> > >> types
> > > > > >> > >> > > (i.e. Produce/Fetch/LeaderReplicatio
> > n/FollowerReplication)
> > > > > >> identify
> > > > > >> > >> the
> > > > > >> > >> > > type of request that are throttled, not the quota
> > mechanism
> > > > > that
> > > > > >> is
> > > > > >> > >> > applied.
> > > > > >> > >> > >
> > > > > >> > >> > > - If a request is throttled due to this
> > > io-thread-unit-based
> > > > > >> quota,
> > > > > >> > is
> > > > > >> > >> > the
> > > > > >> > >> > > existing queue-size metric in ClientQuotaManager
> > > incremented?
> > > > > >> > >> > >
> > > > > >> > >> > > - In the interest of providing guide line for admin to
> > > decide
> > > > > >> > >> > > io-thread-unit-based quota and for user to understand
> its
> > > > > impact
> > > > > >> on
> > > > > >> > >> their
> > > > > >> > >> > > traffic, would it be useful to have a metric that shows
> > the
> > > > > >> overall
> > > > > >> > >> > > byte-rate per io-thread-unit? Can we also show this a
> > > > > >> per-clientId
> > > > > >> > >> > metric?
> > > > > >> > >> > >
> > > > > >> > >> > > Thanks,
> > > > > >> > >> > > Dong
> > > > > >> > >> > >
> > > > > >> > >> > >
> > > > > >> > >> > > On Thu, Feb 23, 2017 at 9:25 AM, Jun Rao <
> > jun@confluent.io
> > > >
> > > > > >> wrote:
> > > > > >> > >> > >
> > > > > >> > >> > >> Hi, Ismael,
> > > > > >> > >> > >>
> > > > > >> > >> > >> For #3, typically, an admin won't configure more io
> > > threads
> > > > > than
> > > > > >> > CPU
> > > > > >> > >> > >> cores,
> > > > > >> > >> > >> but it's possible for an admin to start with fewer io
> > > > threads
> > > > > >> than
> > > > > >> > >> cores
> > > > > >> > >> > >> and grow that later on.
> > > > > >> > >> > >>
> > > > > >> > >> > >> Hi, Dong,
> > > > > >> > >> > >>
> > > > > >> > >> > >> I think the throttleTime sensor on the broker tells
> the
> > > > admin
> > > > > >> > >> whether a
> > > > > >> > >> > >> user/clentId is throttled or not.
> > > > > >> > >> > >>
> > > > > >> > >> > >> Hi, Radi,
> > > > > >> > >> > >>
> > > > > >> > >> > >> The reasoning for delaying the throttled requests on
> the
> > > > > broker
> > > > > >> > >> instead
> > > > > >> > >> > of
> > > > > >> > >> > >> returning an error immediately is that the latter has
> no
> > > way
> > > > > to
> > > > > >> > >> prevent
> > > > > >> > >> > >> the
> > > > > >> > >> > >> client from retrying immediately, which will make
> things
> > > > > worse.
> > > > > >> The
> > > > > >> > >> > >> delaying logic is based off a delay queue. A separate
> > > > > expiration
> > > > > >> > >> thread
> > > > > >> > >> > >> just waits on the next to be expired request. So, it
> > > doesn't
> > > > > tie
> > > > > >> > up a
> > > > > >> > >> > >> request handler thread.
> > > > > >> > >> > >>
> > > > > >> > >> > >> Thanks,
> > > > > >> > >> > >>
> > > > > >> > >> > >> Jun
> > > > > >> > >> > >>
> > > > > >> > >> > >> On Thu, Feb 23, 2017 at 9:07 AM, Ismael Juma <
> > > > > ismael@juma.me.uk
> > > > > >> >
> > > > > >> > >> wrote:
> > > > > >> > >> > >>
> > > > > >> > >> > >> > Hi Jay,
> > > > > >> > >> > >> >
> > > > > >> > >> > >> > Regarding 1, I definitely like the simplicity of
> > > keeping a
> > > > > >> single
> > > > > >> > >> > >> throttle
> > > > > >> > >> > >> > time field in the response. The downside is that the
> > > > client
> > > > > >> > metrics
> > > > > >> > >> > >> will be
> > > > > >> > >> > >> > more coarse grained.
> > > > > >> > >> > >> >
> > > > > >> > >> > >> > Regarding 3, we have `leader.imbalance.per.broker.
> > > > > percentage`
> > > > > >> > and
> > > > > >> > >> > >> > `log.cleaner.min.cleanable.ratio`.
> > > > > >> > >> > >> >
> > > > > >> > >> > >> > Ismael
> > > > > >> > >> > >> >
> > > > > >> > >> > >> > On Thu, Feb 23, 2017 at 4:43 PM, Jay Kreps <
> > > > > jay@confluent.io>
> > > > > >> > >> wrote:
> > > > > >> > >> > >> >
> > > > > >> > >> > >> > > A few minor comments:
> > > > > >> > >> > >> > >
> > > > > >> > >> > >> > >    1. Isn't it the case that the throttling time
> > > > response
> > > > > >> field
> > > > > >> > >> > should
> > > > > >> > >> > >> > have
> > > > > >> > >> > >> > >    the total time your request was throttled
> > > > irrespective
> > > > > of
> > > > > >> > the
> > > > > >> > >> > >> quotas
> > > > > >> > >> > >> > > that
> > > > > >> > >> > >> > >    caused that. Limiting it to byte rate quota
> > doesn't
> > > > > make
> > > > > >> > >> sense,
> > > > > >> > >> > >> but I
> > > > > >> > >> > >> > > also
> > > > > >> > >> > >> > >    I don't think we want to end up adding new
> fields
> > > in
> > > > > the
> > > > > >> > >> response
> > > > > >> > >> > >> for
> > > > > >> > >> > >> > > every
> > > > > >> > >> > >> > >    single thing we quota, right?
> > > > > >> > >> > >> > >    2. I don't think we should make this quota
> > > > specifically
> > > > > >> > about
> > > > > >> > >> io
> > > > > >> > >> > >> > >    threads. Once we introduce these quotas people
> > set
> > > > them
> > > > > >> and
> > > > > >> > >> > expect
> > > > > >> > >> > >> > them
> > > > > >> > >> > >> > > to
> > > > > >> > >> > >> > >    be enforced (and if they aren't it may cause an
> > > > > outage).
> > > > > >> As
> > > > > >> > a
> > > > > >> > >> > >> result
> > > > > >> > >> > >> > > they
> > > > > >> > >> > >> > >    are a bit more sensitive than normal configs, I
> > > > think.
> > > > > >> The
> > > > > >> > >> > current
> > > > > >> > >> > >> > > thread
> > > > > >> > >> > >> > >    pools seem like something of an implementation
> > > detail
> > > > > and
> > > > > >> > not
> > > > > >> > >> the
> > > > > >> > >> > >> > level
> > > > > >> > >> > >> > > the
> > > > > >> > >> > >> > >    user-facing quotas should be involved with. I
> > think
> > > > it
> > > > > >> might
> > > > > >> > >> be
> > > > > >> > >> > >> better
> > > > > >> > >> > >> > > to
> > > > > >> > >> > >> > >    make this a general request-time throttle with
> no
> > > > > >> mention in
> > > > > >> > >> the
> > > > > >> > >> > >> > naming
> > > > > >> > >> > >> > >    about I/O threads and simply acknowledge the
> > > current
> > > > > >> > >> limitation
> > > > > >> > >> > >> (which
> > > > > >> > >> > >> > > we
> > > > > >> > >> > >> > >    may someday fix) in the docs that this covers
> > only
> > > > the
> > > > > >> time
> > > > > >> > >> after
> > > > > >> > >> > >> the
> > > > > >> > >> > >> > >    thread is read off the network.
> > > > > >> > >> > >> > >    3. As such I think the right interface to the
> > user
> > > > > would
> > > > > >> be
> > > > > >> > >> > >> something
> > > > > >> > >> > >> > >    like percent_request_time and be in {0,...100}
> or
> > > > > >> > >> > >> request_time_ratio
> > > > > >> > >> > >> > > and be
> > > > > >> > >> > >> > >    in {0.0,...,1.0} (I think "ratio" is the
> > > terminology
> > > > we
> > > > > >> used
> > > > > >> > >> if
> > > > > >> > >> > the
> > > > > >> > >> > >> > > scale
> > > > > >> > >> > >> > >    is between 0 and 1 in the other metrics,
> right?)
> > > > > >> > >> > >> > >
> > > > > >> > >> > >> > > -Jay
> > > > > >> > >> > >> > >
> > > > > >> > >> > >> > > On Thu, Feb 23, 2017 at 3:45 AM, Rajini Sivaram <
> > > > > >> > >> > >> rajinisivaram@gmail.com
> > > > > >> > >> > >> > >
> > > > > >> > >> > >> > > wrote:
> > > > > >> > >> > >> > >
> > > > > >> > >> > >> > > > Guozhang/Dong,
> > > > > >> > >> > >> > > >
> > > > > >> > >> > >> > > > Thank you for the feedback.
> > > > > >> > >> > >> > > >
> > > > > >> > >> > >> > > > Guozhang : I have updated the section on
> > > co-existence
> > > > of
> > > > > >> byte
> > > > > >> > >> rate
> > > > > >> > >> > >> and
> > > > > >> > >> > >> > > > request time quotas.
> > > > > >> > >> > >> > > >
> > > > > >> > >> > >> > > > Dong: I hadn't added much detail to the metrics
> > and
> > > > > >> sensors
> > > > > >> > >> since
> > > > > >> > >> > >> they
> > > > > >> > >> > >> > > are
> > > > > >> > >> > >> > > > going to be very similar to the existing metrics
> > and
> > > > > >> sensors.
> > > > > >> > >> To
> > > > > >> > >> > >> avoid
> > > > > >> > >> > >> > > > confusion, I have now added more detail. All
> > metrics
> > > > are
> > > > > >> in
> > > > > >> > the
> > > > > >> > >> > >> group
> > > > > >> > >> > >> > > > "quotaType" and all sensors have names starting
> > with
> > > > > >> > >> "quotaType"
> > > > > >> > >> > >> (where
> > > > > >> > >> > >> > > > quotaType is Produce/Fetch/LeaderReplication/
> > > > > >> > >> > >> > > > FollowerReplication/*IOThread*).
> > > > > >> > >> > >> > > > So there will be no reuse of existing
> > > metrics/sensors.
> > > > > The
> > > > > >> > new
> > > > > >> > >> > ones
> > > > > >> > >> > >> for
> > > > > >> > >> > >> > > > request processing time based throttling will be
> > > > > >> completely
> > > > > >> > >> > >> independent
> > > > > >> > >> > >> > > of
> > > > > >> > >> > >> > > > existing metrics/sensors, but will be consistent
> > in
> > > > > >> format.
> > > > > >> > >> > >> > > >
> > > > > >> > >> > >> > > > The existing throttle_time_ms field in
> > produce/fetch
> > > > > >> > responses
> > > > > >> > >> > will
> > > > > >> > >> > >> not
> > > > > >> > >> > >> > > be
> > > > > >> > >> > >> > > > impacted by this KIP. That will continue to
> return
> > > > > >> byte-rate
> > > > > >> > >> based
> > > > > >> > >> > >> > > > throttling times. In addition, a new field
> > > > > >> > >> > request_throttle_time_ms
> > > > > >> > >> > >> > will
> > > > > >> > >> > >> > > be
> > > > > >> > >> > >> > > > added to return request quota based throttling
> > > times.
> > > > > >> These
> > > > > >> > >> will
> > > > > >> > >> > be
> > > > > >> > >> > >> > > exposed
> > > > > >> > >> > >> > > > as new metrics on the client-side.
> > > > > >> > >> > >> > > >
> > > > > >> > >> > >> > > > Since all metrics and sensors are different for
> > each
> > > > > type
> > > > > >> of
> > > > > >> > >> > quota,
> > > > > >> > >> > >> I
> > > > > >> > >> > >> > > > believe there is already sufficient metrics to
> > > monitor
> > > > > >> > >> throttling
> > > > > >> > >> > on
> > > > > >> > >> > >> > both
> > > > > >> > >> > >> > > > client and broker side for each type of
> > throttling.
> > > > > >> > >> > >> > > >
> > > > > >> > >> > >> > > > Regards,
> > > > > >> > >> > >> > > >
> > > > > >> > >> > >> > > > Rajini
> > > > > >> > >> > >> > > >
> > > > > >> > >> > >> > > >
> > > > > >> > >> > >> > > > On Thu, Feb 23, 2017 at 4:32 AM, Dong Lin <
> > > > > >> > lindong28@gmail.com
> > > > > >> > >> >
> > > > > >> > >> > >> wrote:
> > > > > >> > >> > >> > > >
> > > > > >> > >> > >> > > > > Hey Rajini,
> > > > > >> > >> > >> > > > >
> > > > > >> > >> > >> > > > > I think it makes a lot of sense to use
> > > > io_thread_units
> > > > > >> as
> > > > > >> > >> metric
> > > > > >> > >> > >> to
> > > > > >> > >> > >> > > quota
> > > > > >> > >> > >> > > > > user's traffic here. LGTM overall. I have some
> > > > > questions
> > > > > >> > >> > regarding
> > > > > >> > >> > >> > > > sensors.
> > > > > >> > >> > >> > > > >
> > > > > >> > >> > >> > > > > - Can you be more specific in the KIP what
> > sensors
> > > > > will
> > > > > >> be
> > > > > >> > >> > added?
> > > > > >> > >> > >> For
> > > > > >> > >> > >> > > > > example, it will be useful to specify the name
> > and
> > > > > >> > >> attributes of
> > > > > >> > >> > >> > these
> > > > > >> > >> > >> > > > new
> > > > > >> > >> > >> > > > > sensors.
> > > > > >> > >> > >> > > > >
> > > > > >> > >> > >> > > > > - We currently have throttle-time and
> queue-size
> > > for
> > > > > >> > >> byte-rate
> > > > > >> > >> > >> based
> > > > > >> > >> > >> > > > quota.
> > > > > >> > >> > >> > > > > Are you going to have separate throttle-time
> and
> > > > > >> queue-size
> > > > > >> > >> for
> > > > > >> > >> > >> > > requests
> > > > > >> > >> > >> > > > > throttled by io_thread_unit-based quota, or
> will
> > > > they
> > > > > >> share
> > > > > >> > >> the
> > > > > >> > >> > >> same
> > > > > >> > >> > >> > > > > sensor?
> > > > > >> > >> > >> > > > >
> > > > > >> > >> > >> > > > > - Does the throttle-time in the
> ProduceResponse
> > > and
> > > > > >> > >> > FetchResponse
> > > > > >> > >> > >> > > > contains
> > > > > >> > >> > >> > > > > time due to io_thread_unit-based quota?
> > > > > >> > >> > >> > > > >
> > > > > >> > >> > >> > > > > - Currently kafka server doesn't not provide
> any
> > > log
> > > > > or
> > > > > >> > >> metrics
> > > > > >> > >> > >> that
> > > > > >> > >> > >> > > > tells
> > > > > >> > >> > >> > > > > whether any given clientId (or user) is
> > throttled.
> > > > > This
> > > > > >> is
> > > > > >> > >> not
> > > > > >> > >> > too
> > > > > >> > >> > >> > bad
> > > > > >> > >> > >> > > > > because we can still check the client-side
> > > byte-rate
> > > > > >> metric
> > > > > >> > >> to
> > > > > >> > >> > >> > validate
> > > > > >> > >> > >> > > > > whether a given client is throttled. But with
> > this
> > > > > >> > >> > io_thread_unit,
> > > > > >> > >> > >> > > there
> > > > > >> > >> > >> > > > > will be no way to validate whether a given
> > client
> > > is
> > > > > >> slow
> > > > > >> > >> > because
> > > > > >> > >> > >> it
> > > > > >> > >> > >> > > has
> > > > > >> > >> > >> > > > > exceeded its io_thread_unit limit. It is
> > necessary
> > > > for
> > > > > >> user
> > > > > >> > >> to
> > > > > >> > >> > be
> > > > > >> > >> > >> > able
> > > > > >> > >> > >> > > to
> > > > > >> > >> > >> > > > > know this information to figure how whether
> they
> > > > have
> > > > > >> > reached
> > > > > >> > >> > >> there
> > > > > >> > >> > >> > > quota
> > > > > >> > >> > >> > > > > limit. How about we add log4j log on the
> server
> > > side
> > > > > to
> > > > > >> > >> > >> periodically
> > > > > >> > >> > >> > > > print
> > > > > >> > >> > >> > > > > the (client_id, byte-rate-throttle-time,
> > > > > >> > >> > >> > io-thread-unit-throttle-time)
> > > > > >> > >> > >> > > so
> > > > > >> > >> > >> > > > > that kafka administrator can figure those
> users
> > > that
> > > > > >> have
> > > > > >> > >> > reached
> > > > > >> > >> > >> > their
> > > > > >> > >> > >> > > > > limit and act accordingly?
> > > > > >> > >> > >> > > > >
> > > > > >> > >> > >> > > > > Thanks,
> > > > > >> > >> > >> > > > > Dong
> > > > > >> > >> > >> > > > >
> > > > > >> > >> > >> > > > >
> > > > > >> > >> > >> > > > >
> > > > > >> > >> > >> > > > >
> > > > > >> > >> > >> > > > >
> > > > > >> > >> > >> > > > > On Wed, Feb 22, 2017 at 4:46 PM, Guozhang
> Wang <
> > > > > >> > >> > >> wangguoz@gmail.com>
> > > > > >> > >> > >> > > > wrote:
> > > > > >> > >> > >> > > > >
> > > > > >> > >> > >> > > > > > Made a pass over the doc, overall LGTM
> except
> > a
> > > > > minor
> > > > > >> > >> comment
> > > > > >> > >> > on
> > > > > >> > >> > >> > the
> > > > > >> > >> > >> > > > > > throttling implementation:
> > > > > >> > >> > >> > > > > >
> > > > > >> > >> > >> > > > > > Stated as "Request processing time
> throttling
> > > will
> > > > > be
> > > > > >> > >> applied
> > > > > >> > >> > on
> > > > > >> > >> > >> > top
> > > > > >> > >> > >> > > if
> > > > > >> > >> > >> > > > > > necessary." I thought that it meant the
> > request
> > > > > >> > processing
> > > > > >> > >> > time
> > > > > >> > >> > >> > > > > throttling
> > > > > >> > >> > >> > > > > > is applied first, but continue reading I
> found
> > > it
> > > > > >> > actually
> > > > > >> > >> > >> meant to
> > > > > >> > >> > >> > > > apply
> > > > > >> > >> > >> > > > > > produce / fetch byte rate throttling first.
> > > > > >> > >> > >> > > > > >
> > > > > >> > >> > >> > > > > > Also the last sentence "The remaining delay
> if
> > > any
> > > > > is
> > > > > >> > >> applied
> > > > > >> > >> > to
> > > > > >> > >> > >> > the
> > > > > >> > >> > >> > > > > > response." is a bit confusing to me. Maybe
> > > > rewording
> > > > > >> it a
> > > > > >> > >> bit?
> > > > > >> > >> > >> > > > > >
> > > > > >> > >> > >> > > > > >
> > > > > >> > >> > >> > > > > > Guozhang
> > > > > >> > >> > >> > > > > >
> > > > > >> > >> > >> > > > > >
> > > > > >> > >> > >> > > > > > On Wed, Feb 22, 2017 at 3:24 PM, Jun Rao <
> > > > > >> > jun@confluent.io
> > > > > >> > >> >
> > > > > >> > >> > >> wrote:
> > > > > >> > >> > >> > > > > >
> > > > > >> > >> > >> > > > > > > Hi, Rajini,
> > > > > >> > >> > >> > > > > > >
> > > > > >> > >> > >> > > > > > > Thanks for the updated KIP. The latest
> > > proposal
> > > > > >> looks
> > > > > >> > >> good
> > > > > >> > >> > to
> > > > > >> > >> > >> me.
> > > > > >> > >> > >> > > > > > >
> > > > > >> > >> > >> > > > > > > Jun
> > > > > >> > >> > >> > > > > > >
> > > > > >> > >> > >> > > > > > > On Wed, Feb 22, 2017 at 2:19 PM, Rajini
> > > Sivaram
> > > > <
> > > > > >> > >> > >> > > > > rajinisivaram@gmail.com
> > > > > >> > >> > >> > > > > > >
> > > > > >> > >> > >> > > > > > > wrote:
> > > > > >> > >> > >> > > > > > >
> > > > > >> > >> > >> > > > > > > > Jun/Roger,
> > > > > >> > >> > >> > > > > > > >
> > > > > >> > >> > >> > > > > > > > Thank you for the feedback.
> > > > > >> > >> > >> > > > > > > >
> > > > > >> > >> > >> > > > > > > > 1. I have updated the KIP to use
> absolute
> > > > units
> > > > > >> > >> instead of
> > > > > >> > >> > >> > > > > percentage.
> > > > > >> > >> > >> > > > > > > The
> > > > > >> > >> > >> > > > > > > > property is called* io_thread_units* to
> > > align
> > > > > with
> > > > > >> > the
> > > > > >> > >> > >> thread
> > > > > >> > >> > >> > > count
> > > > > >> > >> > >> > > > > > > > property *num.io.threads*. When we
> > implement
> > > > > >> network
> > > > > >> > >> > thread
> > > > > >> > >> > >> > > > > utilization
> > > > > >> > >> > >> > > > > > > > quotas, we can add another property
> > > > > >> > >> > *network_thread_units.*
> > > > > >> > >> > >> > > > > > > >
> > > > > >> > >> > >> > > > > > > > 2. ControlledShutdown is already listed
> > > under
> > > > > the
> > > > > >> > >> exempt
> > > > > >> > >> > >> > > requests.
> > > > > >> > >> > >> > > > > Jun,
> > > > > >> > >> > >> > > > > > > did
> > > > > >> > >> > >> > > > > > > > you mean a different request that needs
> to
> > > be
> > > > > >> added?
> > > > > >> > >> The
> > > > > >> > >> > >> four
> > > > > >> > >> > >> > > > > requests
> > > > > >> > >> > >> > > > > > > > currently exempt in the KIP are
> > StopReplica,
> > > > > >> > >> > >> > ControlledShutdown,
> > > > > >> > >> > >> > > > > > > > LeaderAndIsr and UpdateMetadata. These
> are
> > > > > >> controlled
> > > > > >> > >> > using
> > > > > >> > >> > >> > > > > > ClusterAction
> > > > > >> > >> > >> > > > > > > > ACL, so it is easy to exclude and only
> > > > throttle
> > > > > if
> > > > > >> > >> > >> > unauthorized.
> > > > > >> > >> > >> > > I
> > > > > >> > >> > >> > > > > > wasn't
> > > > > >> > >> > >> > > > > > > > sure if there are other requests used
> only
> > > for
> > > > > >> > >> > inter-broker
> > > > > >> > >> > >> > that
> > > > > >> > >> > >> > > > > needed
> > > > > >> > >> > >> > > > > > > to
> > > > > >> > >> > >> > > > > > > > be excluded.
> > > > > >> > >> > >> > > > > > > >
> > > > > >> > >> > >> > > > > > > > 3. I was thinking the smallest change
> > would
> > > be
> > > > > to
> > > > > >> > >> replace
> > > > > >> > >> > >> all
> > > > > >> > >> > >> > > > > > references
> > > > > >> > >> > >> > > > > > > to
> > > > > >> > >> > >> > > > > > > > *requestChannel.sendResponse()* with a
> > > local
> > > > > >> method
> > > > > >> > >> > >> > > > > > > > *sendResponseMaybeThrottle()* that does
> > the
> > > > > >> > throttling
> > > > > >> > >> if
> > > > > >> > >> > >> any
> > > > > >> > >> > >> > > plus
> > > > > >> > >> > >> > > > > send
> > > > > >> > >> > >> > > > > > > > response. If we throttle first in
> > > > > >> > *KafkaApis.handle()*,
> > > > > >> > >> > the
> > > > > >> > >> > >> > time
> > > > > >> > >> > >> > > > > spent
> > > > > >> > >> > >> > > > > > > > within the method handling the request
> > will
> > > > not
> > > > > be
> > > > > >> > >> > recorded
> > > > > >> > >> > >> or
> > > > > >> > >> > >> > > used
> > > > > >> > >> > >> > > > > in
> > > > > >> > >> > >> > > > > > > > throttling. We can look into this again
> > when
> > > > the
> > > > > >> PR
> > > > > >> > is
> > > > > >> > >> > ready
> > > > > >> > >> > >> > for
> > > > > >> > >> > >> > > > > > review.
> > > > > >> > >> > >> > > > > > > >
> > > > > >> > >> > >> > > > > > > > Regards,
> > > > > >> > >> > >> > > > > > > >
> > > > > >> > >> > >> > > > > > > > Rajini
> > > > > >> > >> > >> > > > > > > >
> > > > > >> > >> > >> > > > > > > >
> > > > > >> > >> > >> > > > > > > >
> > > > > >> > >> > >> > > > > > > > On Wed, Feb 22, 2017 at 5:55 PM, Roger
> > > Hoover
> > > > <
> > > > > >> > >> > >> > > > > roger.hoover@gmail.com>
> > > > > >> > >> > >> > > > > > > > wrote:
> > > > > >> > >> > >> > > > > > > >
> > > > > >> > >> > >> > > > > > > > > Great to see this KIP and the
> excellent
> > > > > >> discussion.
> > > > > >> > >> > >> > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > To me, Jun's suggestion makes sense.
> If
> > > my
> > > > > >> > >> application
> > > > > >> > >> > is
> > > > > >> > >> > >> > > > > allocated
> > > > > >> > >> > >> > > > > > 1
> > > > > >> > >> > >> > > > > > > > > request handler unit, then it's as if
> I
> > > > have a
> > > > > >> > Kafka
> > > > > >> > >> > >> broker
> > > > > >> > >> > >> > > with
> > > > > >> > >> > >> > > > a
> > > > > >> > >> > >> > > > > > > single
> > > > > >> > >> > >> > > > > > > > > request handler thread dedicated to
> me.
> > > > > That's
> > > > > >> the
> > > > > >> > >> > most I
> > > > > >> > >> > >> > can
> > > > > >> > >> > >> > > > use,
> > > > > >> > >> > >> > > > > > at
> > > > > >> > >> > >> > > > > > > > > least.  That allocation doesn't change
> > > even
> > > > if
> > > > > >> an
> > > > > >> > >> admin
> > > > > >> > >> > >> later
> > > > > >> > >> > >> > > > > > increases
> > > > > >> > >> > >> > > > > > > > the
> > > > > >> > >> > >> > > > > > > > > size of the request thread pool on the
> > > > broker.
> > > > > >> > It's
> > > > > >> > >> > >> similar
> > > > > >> > >> > >> > to
> > > > > >> > >> > >> > > > the
> > > > > >> > >> > >> > > > > > CPU
> > > > > >> > >> > >> > > > > > > > > abstraction that VMs and containers
> get
> > > from
> > > > > >> > >> hypervisors
> > > > > >> > >> > >> or
> > > > > >> > >> > >> > OS
> > > > > >> > >> > >> > > > > > > > schedulers.
> > > > > >> > >> > >> > > > > > > > > While different client access patterns
> > can
> > > > use
> > > > > >> > wildly
> > > > > >> > >> > >> > different
> > > > > >> > >> > >> > > > > > amounts
> > > > > >> > >> > >> > > > > > > > of
> > > > > >> > >> > >> > > > > > > > > request thread resources per request,
> a
> > > > given
> > > > > >> > >> > application
> > > > > >> > >> > >> > will
> > > > > >> > >> > >> > > > > > > generally
> > > > > >> > >> > >> > > > > > > > > have a stable access pattern and can
> > > figure
> > > > > out
> > > > > >> > >> > >> empirically
> > > > > >> > >> > >> > how
> > > > > >> > >> > >> > > > > many
> > > > > >> > >> > >> > > > > > > > > "request thread units" it needs to
> meet
> > > it's
> > > > > >> > >> > >> > throughput/latency
> > > > > >> > >> > >> > > > > > goals.
> > > > > >> > >> > >> > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > Cheers,
> > > > > >> > >> > >> > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > Roger
> > > > > >> > >> > >> > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > On Wed, Feb 22, 2017 at 8:53 AM, Jun
> > Rao <
> > > > > >> > >> > >> jun@confluent.io>
> > > > > >> > >> > >> > > > wrote:
> > > > > >> > >> > >> > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > Hi, Rajini,
> > > > > >> > >> > >> > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > Thanks for the updated KIP. A few
> more
> > > > > >> comments.
> > > > > >> > >> > >> > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > 1. A concern of request_time_percent
> > is
> > > > that
> > > > > >> it's
> > > > > >> > >> not
> > > > > >> > >> > an
> > > > > >> > >> > >> > > > absolute
> > > > > >> > >> > >> > > > > > > > value.
> > > > > >> > >> > >> > > > > > > > > > Let's say you give a user a 10%
> limit.
> > > If
> > > > > the
> > > > > >> > admin
> > > > > >> > >> > >> doubles
> > > > > >> > >> > >> > > the
> > > > > >> > >> > >> > > > > > > number
> > > > > >> > >> > >> > > > > > > > of
> > > > > >> > >> > >> > > > > > > > > > request handler threads, that user
> now
> > > > > >> actually
> > > > > >> > has
> > > > > >> > >> > >> twice
> > > > > >> > >> > >> > the
> > > > > >> > >> > >> > > > > > > absolute
> > > > > >> > >> > >> > > > > > > > > > capacity. This may confuse people a
> > bit.
> > > > So,
> > > > > >> > >> perhaps
> > > > > >> > >> > >> > setting
> > > > > >> > >> > >> > > > the
> > > > > >> > >> > >> > > > > > > quota
> > > > > >> > >> > >> > > > > > > > > > based on an absolute request thread
> > unit
> > > > is
> > > > > >> > better.
> > > > > >> > >> > >> > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > 2. ControlledShutdownRequest is also
> > an
> > > > > >> > >> inter-broker
> > > > > >> > >> > >> > request
> > > > > >> > >> > >> > > > and
> > > > > >> > >> > >> > > > > > > needs
> > > > > >> > >> > >> > > > > > > > to
> > > > > >> > >> > >> > > > > > > > > > be excluded from throttling.
> > > > > >> > >> > >> > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > 3. Implementation wise, I am
> wondering
> > > if
> > > > > it's
> > > > > >> > >> simpler
> > > > > >> > >> > >> to
> > > > > >> > >> > >> > > apply
> > > > > >> > >> > >> > > > > the
> > > > > >> > >> > >> > > > > > > > > request
> > > > > >> > >> > >> > > > > > > > > > time throttling first in
> > > > KafkaApis.handle().
> > > > > >> > >> > Otherwise,
> > > > > >> > >> > >> we
> > > > > >> > >> > >> > > will
> > > > > >> > >> > >> > > > > > need
> > > > > >> > >> > >> > > > > > > to
> > > > > >> > >> > >> > > > > > > > > add
> > > > > >> > >> > >> > > > > > > > > > the throttling logic in each type of
> > > > > request.
> > > > > >> > >> > >> > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > Thanks,
> > > > > >> > >> > >> > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > Jun
> > > > > >> > >> > >> > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > On Wed, Feb 22, 2017 at 5:58 AM,
> > Rajini
> > > > > >> Sivaram <
> > > > > >> > >> > >> > > > > > > > rajinisivaram@gmail.com
> > > > > >> > >> > >> > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > wrote:
> > > > > >> > >> > >> > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > Jun,
> > > > > >> > >> > >> > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > Thank you for the review.
> > > > > >> > >> > >> > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > I have reverted to the original
> KIP
> > > that
> > > > > >> > >> throttles
> > > > > >> > >> > >> based
> > > > > >> > >> > >> > on
> > > > > >> > >> > >> > > > > > request
> > > > > >> > >> > >> > > > > > > > > > handler
> > > > > >> > >> > >> > > > > > > > > > > utilization. At the moment, it
> uses
> > > > > >> percentage,
> > > > > >> > >> but
> > > > > >> > >> > I
> > > > > >> > >> > >> am
> > > > > >> > >> > >> > > > happy
> > > > > >> > >> > >> > > > > to
> > > > > >> > >> > >> > > > > > > > > change
> > > > > >> > >> > >> > > > > > > > > > to
> > > > > >> > >> > >> > > > > > > > > > > a fraction (out of 1 instead of
> 100)
> > > if
> > > > > >> > >> required. I
> > > > > >> > >> > >> have
> > > > > >> > >> > >> > > > added
> > > > > >> > >> > >> > > > > > the
> > > > > >> > >> > >> > > > > > > > > > examples
> > > > > >> > >> > >> > > > > > > > > > > from this discussion to the KIP.
> > Also
> > > > > added
> > > > > >> a
> > > > > >> > >> > "Future
> > > > > >> > >> > >> > Work"
> > > > > >> > >> > >> > > > > > section
> > > > > >> > >> > >> > > > > > > > to
> > > > > >> > >> > >> > > > > > > > > > > address network thread
> utilization.
> > > The
> > > > > >> > >> > configuration
> > > > > >> > >> > >> is
> > > > > >> > >> > >> > > > named
> > > > > >> > >> > >> > > > > > > > > > > "request_time_percent" with the
> > > > > expectation
> > > > > >> > that
> > > > > >> > >> it
> > > > > >> > >> > >> can
> > > > > >> > >> > >> > > also
> > > > > >> > >> > >> > > > be
> > > > > >> > >> > >> > > > > > > used
> > > > > >> > >> > >> > > > > > > > as
> > > > > >> > >> > >> > > > > > > > > > the
> > > > > >> > >> > >> > > > > > > > > > > limit for network thread
> utilization
> > > > when
> > > > > >> that
> > > > > >> > is
> > > > > >> > >> > >> > > > implemented,
> > > > > >> > >> > >> > > > > so
> > > > > >> > >> > >> > > > > > > > that
> > > > > >> > >> > >> > > > > > > > > > > users have to set only one config
> > for
> > > > the
> > > > > >> two
> > > > > >> > and
> > > > > >> > >> > not
> > > > > >> > >> > >> > have
> > > > > >> > >> > >> > > to
> > > > > >> > >> > >> > > > > > worry
> > > > > >> > >> > >> > > > > > > > > about
> > > > > >> > >> > >> > > > > > > > > > > the internal distribution of the
> > work
> > > > > >> between
> > > > > >> > the
> > > > > >> > >> > two
> > > > > >> > >> > >> > > thread
> > > > > >> > >> > >> > > > > > pools
> > > > > >> > >> > >> > > > > > > in
> > > > > >> > >> > >> > > > > > > > > > > Kafka.
> > > > > >> > >> > >> > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > Regards,
> > > > > >> > >> > >> > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > Rajini
> > > > > >> > >> > >> > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > On Wed, Feb 22, 2017 at 12:23 AM,
> > Jun
> > > > Rao
> > > > > <
> > > > > >> > >> > >> > > jun@confluent.io>
> > > > > >> > >> > >> > > > > > > wrote:
> > > > > >> > >> > >> > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > Hi, Rajini,
> > > > > >> > >> > >> > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > Thanks for the proposal.
> > > > > >> > >> > >> > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > The benefit of using the request
> > > > > >> processing
> > > > > >> > >> time
> > > > > >> > >> > >> over
> > > > > >> > >> > >> > the
> > > > > >> > >> > >> > > > > > request
> > > > > >> > >> > >> > > > > > > > > rate
> > > > > >> > >> > >> > > > > > > > > > is
> > > > > >> > >> > >> > > > > > > > > > > > exactly what people have said. I
> > > will
> > > > > just
> > > > > >> > >> expand
> > > > > >> > >> > >> that
> > > > > >> > >> > >> > a
> > > > > >> > >> > >> > > > bit.
> > > > > >> > >> > >> > > > > > > > > Consider
> > > > > >> > >> > >> > > > > > > > > > > the
> > > > > >> > >> > >> > > > > > > > > > > > following case. The producer
> > sends a
> > > > > >> produce
> > > > > >> > >> > request
> > > > > >> > >> > >> > > with a
> > > > > >> > >> > >> > > > > > 10MB
> > > > > >> > >> > >> > > > > > > > > > message
> > > > > >> > >> > >> > > > > > > > > > > > but compressed to 100KB with
> gzip.
> > > The
> > > > > >> > >> > >> decompression of
> > > > > >> > >> > >> > > the
> > > > > >> > >> > >> > > > > > > message
> > > > > >> > >> > >> > > > > > > > > on
> > > > > >> > >> > >> > > > > > > > > > > the
> > > > > >> > >> > >> > > > > > > > > > > > broker could take 10-15 seconds,
> > > > during
> > > > > >> which
> > > > > >> > >> > time,
> > > > > >> > >> > >> a
> > > > > >> > >> > >> > > > request
> > > > > >> > >> > >> > > > > > > > handler
> > > > > >> > >> > >> > > > > > > > > > > > thread is completely blocked. In
> > > this
> > > > > >> case,
> > > > > >> > >> > neither
> > > > > >> > >> > >> the
> > > > > >> > >> > >> > > > > byte-in
> > > > > >> > >> > >> > > > > > > > quota
> > > > > >> > >> > >> > > > > > > > > > nor
> > > > > >> > >> > >> > > > > > > > > > > > the request rate quota may be
> > > > effective
> > > > > in
> > > > > >> > >> > >> protecting
> > > > > >> > >> > >> > the
> > > > > >> > >> > >> > > > > > broker.
> > > > > >> > >> > >> > > > > > > > > > > Consider
> > > > > >> > >> > >> > > > > > > > > > > > another case. A consumer group
> > > starts
> > > > > >> with 10
> > > > > >> > >> > >> instances
> > > > > >> > >> > >> > > and
> > > > > >> > >> > >> > > > > > later
> > > > > >> > >> > >> > > > > > > > on
> > > > > >> > >> > >> > > > > > > > > > > > switches to 20 instances. The
> > > request
> > > > > rate
> > > > > >> > will
> > > > > >> > >> > >> likely
> > > > > >> > >> > >> > > > > double,
> > > > > >> > >> > >> > > > > > > but
> > > > > >> > >> > >> > > > > > > > > the
> > > > > >> > >> > >> > > > > > > > > > > > actually load on the broker may
> > not
> > > > > double
> > > > > >> > >> since
> > > > > >> > >> > >> each
> > > > > >> > >> > >> > > fetch
> > > > > >> > >> > >> > > > > > > request
> > > > > >> > >> > >> > > > > > > > > > only
> > > > > >> > >> > >> > > > > > > > > > > > contains half of the partitions.
> > > > Request
> > > > > >> rate
> > > > > >> > >> > quota
> > > > > >> > >> > >> may
> > > > > >> > >> > >> > > not
> > > > > >> > >> > >> > > > > be
> > > > > >> > >> > >> > > > > > > easy
> > > > > >> > >> > >> > > > > > > > > to
> > > > > >> > >> > >> > > > > > > > > > > > configure in this case.
> > > > > >> > >> > >> > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > What we really want is to be
> able
> > to
> > > > > >> prevent
> > > > > >> > a
> > > > > >> > >> > >> client
> > > > > >> > >> > >> > > from
> > > > > >> > >> > >> > > > > > using
> > > > > >> > >> > >> > > > > > > > too
> > > > > >> > >> > >> > > > > > > > > > much
> > > > > >> > >> > >> > > > > > > > > > > > of the server side resources. In
> > > this
> > > > > >> > >> particular
> > > > > >> > >> > >> KIP,
> > > > > >> > >> > >> > > this
> > > > > >> > >> > >> > > > > > > resource
> > > > > >> > >> > >> > > > > > > > > is
> > > > > >> > >> > >> > > > > > > > > > > the
> > > > > >> > >> > >> > > > > > > > > > > > capacity of the request handler
> > > > > threads. I
> > > > > >> > >> agree
> > > > > >> > >> > >> that
> > > > > >> > >> > >> > it
> > > > > >> > >> > >> > > > may
> > > > > >> > >> > >> > > > > > not
> > > > > >> > >> > >> > > > > > > be
> > > > > >> > >> > >> > > > > > > > > > > > intuitive for the users to
> > determine
> > > > how
> > > > > >> to
> > > > > >> > set
> > > > > >> > >> > the
> > > > > >> > >> > >> > right
> > > > > >> > >> > >> > > > > > limit.
> > > > > >> > >> > >> > > > > > > > > > However,
> > > > > >> > >> > >> > > > > > > > > > > > this is not completely new and
> has
> > > > been
> > > > > >> done
> > > > > >> > in
> > > > > >> > >> > the
> > > > > >> > >> > >> > > > container
> > > > > >> > >> > >> > > > > > > world
> > > > > >> > >> > >> > > > > > > > > > > > already. For example, Linux
> > cgroup (
> > > > > >> > >> > >> > > > > https://access.redhat.com/
> > > > > >> > >> > >> > > > > > > > > > > > documentation/en-US/Red_Hat_En
> > > > > >> > >> > >> terprise_Linux/6/html/
> > > > > >> > >> > >> > > > > > > > > > > > Resource_Management_Guide/sec-
> > > > cpu.html)
> > > > > >> has
> > > > > >> > >> the
> > > > > >> > >> > >> > concept
> > > > > >> > >> > >> > > of
> > > > > >> > >> > >> > > > > > > > > > > > cpu.cfs_quota_us,
> > > > > >> > >> > >> > > > > > > > > > > > which specifies the total amount
> > of
> > > > time
> > > > > >> in
> > > > > >> > >> > >> > microseconds
> > > > > >> > >> > >> > > > for
> > > > > >> > >> > >> > > > > > > which
> > > > > >> > >> > >> > > > > > > > > all
> > > > > >> > >> > >> > > > > > > > > > > > tasks in a cgroup can run
> during a
> > > one
> > > > > >> second
> > > > > >> > >> > >> period.
> > > > > >> > >> > >> > We
> > > > > >> > >> > >> > > > can
> > > > > >> > >> > >> > > > > > > > > > potentially
> > > > > >> > >> > >> > > > > > > > > > > > model the request handler
> threads
> > > in a
> > > > > >> > similar
> > > > > >> > >> > way.
> > > > > >> > >> > >> For
> > > > > >> > >> > >> > > > > > example,
> > > > > >> > >> > >> > > > > > > > each
> > > > > >> > >> > >> > > > > > > > > > > > request handler thread can be 1
> > > > request
> > > > > >> > handler
> > > > > >> > >> > unit
> > > > > >> > >> > >> > and
> > > > > >> > >> > >> > > > the
> > > > > >> > >> > >> > > > > > > admin
> > > > > >> > >> > >> > > > > > > > > can
> > > > > >> > >> > >> > > > > > > > > > > > configure a limit on how many
> > units
> > > > (say
> > > > > >> > 0.01)
> > > > > >> > >> a
> > > > > >> > >> > >> client
> > > > > >> > >> > >> > > can
> > > > > >> > >> > >> > > > > > have.
> > > > > >> > >> > >> > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > Regarding not throttling the
> > > internal
> > > > > >> broker
> > > > > >> > to
> > > > > >> > >> > >> broker
> > > > > >> > >> > >> > > > > > requests.
> > > > > >> > >> > >> > > > > > > We
> > > > > >> > >> > >> > > > > > > > > > could
> > > > > >> > >> > >> > > > > > > > > > > > do that. Alternatively, we could
> > > just
> > > > > let
> > > > > >> the
> > > > > >> > >> > admin
> > > > > >> > >> > >> > > > > configure a
> > > > > >> > >> > >> > > > > > > > high
> > > > > >> > >> > >> > > > > > > > > > > limit
> > > > > >> > >> > >> > > > > > > > > > > > for the kafka user (it may not
> be
> > > able
> > > > > to
> > > > > >> do
> > > > > >> > >> that
> > > > > >> > >> > >> > easily
> > > > > >> > >> > >> > > > > based
> > > > > >> > >> > >> > > > > > on
> > > > > >> > >> > >> > > > > > > > > > > clientId
> > > > > >> > >> > >> > > > > > > > > > > > though).
> > > > > >> > >> > >> > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > Ideally we want to be able to
> > > protect
> > > > > the
> > > > > >> > >> > >> utilization
> > > > > >> > >> > >> > of
> > > > > >> > >> > >> > > > the
> > > > > >> > >> > >> > > > > > > > network
> > > > > >> > >> > >> > > > > > > > > > > thread
> > > > > >> > >> > >> > > > > > > > > > > > pool too. The difficult is
> mostly
> > > what
> > > > > >> Rajini
> > > > > >> > >> > said:
> > > > > >> > >> > >> (1)
> > > > > >> > >> > >> > > The
> > > > > >> > >> > >> > > > > > > > mechanism
> > > > > >> > >> > >> > > > > > > > > > for
> > > > > >> > >> > >> > > > > > > > > > > > throttling the requests is
> through
> > > > > >> Purgatory
> > > > > >> > >> and
> > > > > >> > >> > we
> > > > > >> > >> > >> > will
> > > > > >> > >> > >> > > > have
> > > > > >> > >> > >> > > > > > to
> > > > > >> > >> > >> > > > > > > > > think
> > > > > >> > >> > >> > > > > > > > > > > > through how to integrate that
> into
> > > the
> > > > > >> > network
> > > > > >> > >> > >> layer.
> > > > > >> > >> > >> > > (2)
> > > > > >> > >> > >> > > > In
> > > > > >> > >> > >> > > > > > the
> > > > > >> > >> > >> > > > > > > > > > network
> > > > > >> > >> > >> > > > > > > > > > > > layer, currently we know the
> user,
> > > but
> > > > > not
> > > > > >> > the
> > > > > >> > >> > >> clientId
> > > > > >> > >> > >> > > of
> > > > > >> > >> > >> > > > > the
> > > > > >> > >> > >> > > > > > > > > request.
> > > > > >> > >> > >> > > > > > > > > > > So,
> > > > > >> > >> > >> > > > > > > > > > > > it's a bit tricky to throttle
> > based
> > > on
> > > > > >> > clientId
> > > > > >> > >> > >> there.
> > > > > >> > >> > >> > > > Plus,
> > > > > >> > >> > >> > > > > > the
> > > > > >> > >> > >> > > > > > > > > > byteOut
> > > > > >> > >> > >> > > > > > > > > > > > quota can already protect the
> > > network
> > > > > >> thread
> > > > > >> > >> > >> > utilization
> > > > > >> > >> > >> > > > for
> > > > > >> > >> > >> > > > > > > fetch
> > > > > >> > >> > >> > > > > > > > > > > > requests. So, if we can't figure
> > out
> > > > > this
> > > > > >> > part
> > > > > >> > >> > right
> > > > > >> > >> > >> > now,
> > > > > >> > >> > >> > > > > just
> > > > > >> > >> > >> > > > > > > > > focusing
> > > > > >> > >> > >> > > > > > > > > > > on
> > > > > >> > >> > >> > > > > > > > > > > > the request handling threads for
> > > this
> > > > > KIP
> > > > > >> is
> > > > > >> > >> > still a
> > > > > >> > >> > >> > > useful
> > > > > >> > >> > >> > > > > > > > feature.
> > > > > >> > >> > >> > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > Thanks,
> > > > > >> > >> > >> > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > Jun
> > > > > >> > >> > >> > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > On Tue, Feb 21, 2017 at 4:27 AM,
> > > > Rajini
> > > > > >> > >> Sivaram <
> > > > > >> > >> > >> > > > > > > > > > rajinisivaram@gmail.com
> > > > > >> > >> > >> > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > wrote:
> > > > > >> > >> > >> > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > Thank you all for the
> feedback.
> > > > > >> > >> > >> > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > Jay: I have removed exemption
> > for
> > > > > >> consumer
> > > > > >> > >> > >> heartbeat
> > > > > >> > >> > >> > > etc.
> > > > > >> > >> > >> > > > > > Agree
> > > > > >> > >> > >> > > > > > > > > that
> > > > > >> > >> > >> > > > > > > > > > > > > protecting the cluster is more
> > > > > important
> > > > > >> > than
> > > > > >> > >> > >> > > protecting
> > > > > >> > >> > >> > > > > > > > individual
> > > > > >> > >> > >> > > > > > > > > > > apps.
> > > > > >> > >> > >> > > > > > > > > > > > > Have retained the exemption
> for
> > > > > >> > >> > >> > > StopReplicat/LeaderAndIsr
> > > > > >> > >> > >> > > > > > etc,
> > > > > >> > >> > >> > > > > > > > > these
> > > > > >> > >> > >> > > > > > > > > > > are
> > > > > >> > >> > >> > > > > > > > > > > > > throttled only if
> authorization
> > > > fails
> > > > > >> (so
> > > > > >> > >> can't
> > > > > >> > >> > be
> > > > > >> > >> > >> > used
> > > > > >> > >> > >> > > > for
> > > > > >> > >> > >> > > > > > DoS
> > > > > >> > >> > >> > > > > > > > > > attacks
> > > > > >> > >> > >> > > > > > > > > > > > in
> > > > > >> > >> > >> > > > > > > > > > > > > a secure cluster, but allows
> > > > > >> inter-broker
> > > > > >> > >> > >> requests to
> > > > > >> > >> > >> > > > > > complete
> > > > > >> > >> > >> > > > > > > > > > without
> > > > > >> > >> > >> > > > > > > > > > > > > delays).
> > > > > >> > >> > >> > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > I will wait another day to see
> > if
> > > > > these
> > > > > >> is
> > > > > >> > >> any
> > > > > >> > >> > >> > > objection
> > > > > >> > >> > >> > > > to
> > > > > >> > >> > >> > > > > > > > quotas
> > > > > >> > >> > >> > > > > > > > > > > based
> > > > > >> > >> > >> > > > > > > > > > > > on
> > > > > >> > >> > >> > > > > > > > > > > > > request processing time (as
> > > opposed
> > > > to
> > > > > >> > >> request
> > > > > >> > >> > >> rate)
> > > > > >> > >> > >> > > and
> > > > > >> > >> > >> > > > if
> > > > > >> > >> > >> > > > > > > there
> > > > > >> > >> > >> > > > > > > > > are
> > > > > >> > >> > >> > > > > > > > > > > no
> > > > > >> > >> > >> > > > > > > > > > > > > objections, I will revert to
> the
> > > > > >> original
> > > > > >> > >> > proposal
> > > > > >> > >> > >> > with
> > > > > >> > >> > >> > > > > some
> > > > > >> > >> > >> > > > > > > > > changes.
> > > > > >> > >> > >> > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > The original proposal was only
> > > > > including
> > > > > >> > the
> > > > > >> > >> > time
> > > > > >> > >> > >> > used
> > > > > >> > >> > >> > > by
> > > > > >> > >> > >> > > > > the
> > > > > >> > >> > >> > > > > > > > > request
> > > > > >> > >> > >> > > > > > > > > > > > > handler threads (that made
> > > > calculation
> > > > > >> > >> easy). I
> > > > > >> > >> > >> think
> > > > > >> > >> > >> > > the
> > > > > >> > >> > >> > > > > > > > > suggestion
> > > > > >> > >> > >> > > > > > > > > > is
> > > > > >> > >> > >> > > > > > > > > > > > to
> > > > > >> > >> > >> > > > > > > > > > > > > include the time spent in the
> > > > network
> > > > > >> > >> threads as
> > > > > >> > >> > >> well
> > > > > >> > >> > >> > > > since
> > > > > >> > >> > >> > > > > > > that
> > > > > >> > >> > >> > > > > > > > > may
> > > > > >> > >> > >> > > > > > > > > > be
> > > > > >> > >> > >> > > > > > > > > > > > > significant. As Jay pointed
> out,
> > > it
> > > > is
> > > > > >> more
> > > > > >> > >> > >> > complicated
> > > > > >> > >> > >> > > > to
> > > > > >> > >> > >> > > > > > > > > calculate
> > > > > >> > >> > >> > > > > > > > > > > the
> > > > > >> > >> > >> > > > > > > > > > > > > total available CPU time and
> > > convert
> > > > > to
> > > > > >> a
> > > > > >> > >> ratio
> > > > > >> > >> > >> when
> > > > > >> > >> > >> > > > there
> > > > > >> > >> > >> > > > > > *m*
> > > > > >> > >> > >> > > > > > > > I/O
> > > > > >> > >> > >> > > > > > > > > > > > threads
> > > > > >> > >> > >> > > > > > > > > > > > > and *n* network threads.
> > > > > >> > >> > >> > ThreadMXBean#getThreadCPUTime(
> > > > > >> > >> > >> > > )
> > > > > >> > >> > >> > > > > may
> > > > > >> > >> > >> > > > > > > > give
> > > > > >> > >> > >> > > > > > > > > us
> > > > > >> > >> > >> > > > > > > > > > > > what
> > > > > >> > >> > >> > > > > > > > > > > > > we want, but it can be very
> > > > expensive
> > > > > on
> > > > > >> > some
> > > > > >> > >> > >> > > platforms.
> > > > > >> > >> > >> > > > As
> > > > > >> > >> > >> > > > > > > > Becket
> > > > > >> > >> > >> > > > > > > > > > and
> > > > > >> > >> > >> > > > > > > > > > > > > Guozhang have pointed out, we
> do
> > > > have
> > > > > >> > several
> > > > > >> > >> > time
> > > > > >> > >> > >> > > > > > measurements
> > > > > >> > >> > >> > > > > > > > > > already
> > > > > >> > >> > >> > > > > > > > > > > > for
> > > > > >> > >> > >> > > > > > > > > > > > > generating metrics that we
> could
> > > > use,
> > > > > >> > though
> > > > > >> > >> we
> > > > > >> > >> > >> might
> > > > > >> > >> > >> > > > want
> > > > > >> > >> > >> > > > > to
> > > > > >> > >> > >> > > > > > > > > switch
> > > > > >> > >> > >> > > > > > > > > > to
> > > > > >> > >> > >> > > > > > > > > > > > > nanoTime() instead of
> > > > > >> currentTimeMillis()
> > > > > >> > >> since
> > > > > >> > >> > >> some
> > > > > >> > >> > >> > of
> > > > > >> > >> > >> > > > the
> > > > > >> > >> > >> > > > > > > > values
> > > > > >> > >> > >> > > > > > > > > > for
> > > > > >> > >> > >> > > > > > > > > > > > > small requests may be < 1ms.
> But
> > > > > rather
> > > > > >> > than
> > > > > >> > >> add
> > > > > >> > >> > >> up
> > > > > >> > >> > >> > the
> > > > > >> > >> > >> > > > > time
> > > > > >> > >> > >> > > > > > > > spent
> > > > > >> > >> > >> > > > > > > > > in
> > > > > >> > >> > >> > > > > > > > > > > I/O
> > > > > >> > >> > >> > > > > > > > > > > > > thread and network thread,
> > > wouldn't
> > > > it
> > > > > >> be
> > > > > >> > >> better
> > > > > >> > >> > >> to
> > > > > >> > >> > >> > > > convert
> > > > > >> > >> > >> > > > > > the
> > > > > >> > >> > >> > > > > > > > > time
> > > > > >> > >> > >> > > > > > > > > > > > spent
> > > > > >> > >> > >> > > > > > > > > > > > > on each thread into a separate
> > > > ratio?
> > > > > >> UserA
> > > > > >> > >> has
> > > > > >> > >> > a
> > > > > >> > >> > >> > > request
> > > > > >> > >> > >> > > > > > quota
> > > > > >> > >> > >> > > > > > > > of
> > > > > >> > >> > >> > > > > > > > > > 5%.
> > > > > >> > >> > >> > > > > > > > > > > > Can
> > > > > >> > >> > >> > > > > > > > > > > > > we take that to mean that
> UserA
> > > can
> > > > > use
> > > > > >> 5%
> > > > > >> > of
> > > > > >> > >> > the
> > > > > >> > >> > >> > time
> > > > > >> > >> > >> > > on
> > > > > >> > >> > >> > > > > > > network
> > > > > >> > >> > >> > > > > > > > > > > threads
> > > > > >> > >> > >> > > > > > > > > > > > > and 5% of the time on I/O
> > threads?
> > > > If
> > > > > >> > either
> > > > > >> > >> is
> > > > > >> > >> > >> > > exceeded,
> > > > > >> > >> > >> > > > > the
> > > > > >> > >> > >> > > > > > > > > > response
> > > > > >> > >> > >> > > > > > > > > > > is
> > > > > >> > >> > >> > > > > > > > > > > > > throttled - it would mean
> > > > maintaining
> > > > > >> two
> > > > > >> > >> sets
> > > > > >> > >> > of
> > > > > >> > >> > >> > > metrics
> > > > > >> > >> > >> > > > > for
> > > > > >> > >> > >> > > > > > > the
> > > > > >> > >> > >> > > > > > > > > two
> > > > > >> > >> > >> > > > > > > > > > > > > durations, but would result in
> > > more
> > > > > >> > >> meaningful
> > > > > >> > >> > >> > ratios.
> > > > > >> > >> > >> > > We
> > > > > >> > >> > >> > > > > > could
> > > > > >> > >> > >> > > > > > > > > > define
> > > > > >> > >> > >> > > > > > > > > > > > two
> > > > > >> > >> > >> > > > > > > > > > > > > quota limits (UserA has 5% of
> > > > request
> > > > > >> > threads
> > > > > >> > >> > and
> > > > > >> > >> > >> 10%
> > > > > >> > >> > >> > > of
> > > > > >> > >> > >> > > > > > > network
> > > > > >> > >> > >> > > > > > > > > > > > threads),
> > > > > >> > >> > >> > > > > > > > > > > > > but that seems unnecessary and
> > > > harder
> > > > > to
> > > > > >> > >> explain
> > > > > >> > >> > >> to
> > > > > >> > >> > >> > > > users.
> > > > > >> > >> > >> > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > Back to why and how quotas are
> > > > applied
> > > > > >> to
> > > > > >> > >> > network
> > > > > >> > >> > >> > > thread
> > > > > >> > >> > >> > > > > > > > > utilization:
> > > > > >> > >> > >> > > > > > > > > > > > > a) In the case of fetch,  the
> > time
> > > > > >> spent in
> > > > > >> > >> the
> > > > > >> > >> > >> > network
> > > > > >> > >> > >> > > > > > thread
> > > > > >> > >> > >> > > > > > > > may
> > > > > >> > >> > >> > > > > > > > > be
> > > > > >> > >> > >> > > > > > > > > > > > > significant and I can see the
> > need
> > > > to
> > > > > >> > include
> > > > > >> > >> > >> this.
> > > > > >> > >> > >> > Are
> > > > > >> > >> > >> > > > > there
> > > > > >> > >> > >> > > > > > > > other
> > > > > >> > >> > >> > > > > > > > > > > > > requests where the network
> > thread
> > > > > >> > >> utilization is
> > > > > >> > >> > >> > > > > significant?
> > > > > >> > >> > >> > > > > > > In
> > > > > >> > >> > >> > > > > > > > > the
> > > > > >> > >> > >> > > > > > > > > > > case
> > > > > >> > >> > >> > > > > > > > > > > > > of fetch, request handler
> thread
> > > > > >> > utilization
> > > > > >> > >> > would
> > > > > >> > >> > >> > > > throttle
> > > > > >> > >> > >> > > > > > > > clients
> > > > > >> > >> > >> > > > > > > > > > > with
> > > > > >> > >> > >> > > > > > > > > > > > > high request rate, low data
> > volume
> > > > and
> > > > > >> > fetch
> > > > > >> > >> > byte
> > > > > >> > >> > >> > rate
> > > > > >> > >> > >> > > > > quota
> > > > > >> > >> > >> > > > > > > will
> > > > > >> > >> > >> > > > > > > > > > > > throttle
> > > > > >> > >> > >> > > > > > > > > > > > > clients with high data volume.
> > > > Network
> > > > > >> > thread
> > > > > >> > >> > >> > > utilization
> > > > > >> > >> > >> > > > > is
> > > > > >> > >> > >> > > > > > > > > perhaps
> > > > > >> > >> > >> > > > > > > > > > > > > proportional to the data
> > volume. I
> > > > am
> > > > > >> > >> wondering
> > > > > >> > >> > >> if we
> > > > > >> > >> > >> > > > even
> > > > > >> > >> > >> > > > > > need
> > > > > >> > >> > >> > > > > > > > to
> > > > > >> > >> > >> > > > > > > > > > > > throttle
> > > > > >> > >> > >> > > > > > > > > > > > > based on network thread
> > > utilization
> > > > or
> > > > > >> > >> whether
> > > > > >> > >> > the
> > > > > >> > >> > >> > data
> > > > > >> > >> > >> > > > > > volume
> > > > > >> > >> > >> > > > > > > > > quota
> > > > > >> > >> > >> > > > > > > > > > > > covers
> > > > > >> > >> > >> > > > > > > > > > > > > this case.
> > > > > >> > >> > >> > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > b) At the moment, we record
> and
> > > > check
> > > > > >> for
> > > > > >> > >> quota
> > > > > >> > >> > >> > > violation
> > > > > >> > >> > >> > > > > at
> > > > > >> > >> > >> > > > > > > the
> > > > > >> > >> > >> > > > > > > > > same
> > > > > >> > >> > >> > > > > > > > > > > > time.
> > > > > >> > >> > >> > > > > > > > > > > > > If a quota is violated, the
> > > response
> > > > > is
> > > > > >> > >> delayed.
> > > > > >> > >> > >> > Using
> > > > > >> > >> > >> > > > > Jay'e
> > > > > >> > >> > >> > > > > > > > > example
> > > > > >> > >> > >> > > > > > > > > > of
> > > > > >> > >> > >> > > > > > > > > > > > > disk reads for fetches
> happening
> > > in
> > > > > the
> > > > > >> > >> network
> > > > > >> > >> > >> > thread,
> > > > > >> > >> > >> > > > We
> > > > > >> > >> > >> > > > > > > can't
> > > > > >> > >> > >> > > > > > > > > > record
> > > > > >> > >> > >> > > > > > > > > > > > and
> > > > > >> > >> > >> > > > > > > > > > > > > delay a response after the
> disk
> > > > reads.
> > > > > >> We
> > > > > >> > >> could
> > > > > >> > >> > >> > record
> > > > > >> > >> > >> > > > the
> > > > > >> > >> > >> > > > > > time
> > > > > >> > >> > >> > > > > > > > > spent
> > > > > >> > >> > >> > > > > > > > > > > on
> > > > > >> > >> > >> > > > > > > > > > > > > the network thread when the
> > > response
> > > > > is
> > > > > >> > >> complete
> > > > > >> > >> > >> and
> > > > > >> > >> > >> > > > > > introduce
> > > > > >> > >> > >> > > > > > > a
> > > > > >> > >> > >> > > > > > > > > > delay
> > > > > >> > >> > >> > > > > > > > > > > > for
> > > > > >> > >> > >> > > > > > > > > > > > > handling a subsequent request
> > > > > (separate
> > > > > >> out
> > > > > >> > >> > >> recording
> > > > > >> > >> > >> > > and
> > > > > >> > >> > >> > > > > > quota
> > > > > >> > >> > >> > > > > > > > > > > violation
> > > > > >> > >> > >> > > > > > > > > > > > > handling in the case of
> network
> > > > thread
> > > > > >> > >> > overload).
> > > > > >> > >> > >> > Does
> > > > > >> > >> > >> > > > that
> > > > > >> > >> > >> > > > > > > make
> > > > > >> > >> > >> > > > > > > > > > sense?
> > > > > >> > >> > >> > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > Regards,
> > > > > >> > >> > >> > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > Rajini
> > > > > >> > >> > >> > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > On Tue, Feb 21, 2017 at 2:58
> AM,
> > > > > Becket
> > > > > >> > Qin <
> > > > > >> > >> > >> > > > > > > > becket.qin@gmail.com>
> > > > > >> > >> > >> > > > > > > > > > > > wrote:
> > > > > >> > >> > >> > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > > Hey Jay,
> > > > > >> > >> > >> > > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > > Yeah, I agree that enforcing
> > the
> > > > CPU
> > > > > >> time
> > > > > >> > >> is a
> > > > > >> > >> > >> > little
> > > > > >> > >> > >> > > > > > > tricky. I
> > > > > >> > >> > >> > > > > > > > > am
> > > > > >> > >> > >> > > > > > > > > > > > > thinking
> > > > > >> > >> > >> > > > > > > > > > > > > > that maybe we can use the
> > > existing
> > > > > >> > request
> > > > > >> > >> > >> > > statistics.
> > > > > >> > >> > >> > > > > They
> > > > > >> > >> > >> > > > > > > are
> > > > > >> > >> > >> > > > > > > > > > > already
> > > > > >> > >> > >> > > > > > > > > > > > > > very detailed so we can
> > probably
> > > > see
> > > > > >> the
> > > > > >> > >> > >> > approximate
> > > > > >> > >> > >> > > > CPU
> > > > > >> > >> > >> > > > > > time
> > > > > >> > >> > >> > > > > > > > > from
> > > > > >> > >> > >> > > > > > > > > > > it,
> > > > > >> > >> > >> > > > > > > > > > > > > e.g.
> > > > > >> > >> > >> > > > > > > > > > > > > > something like (total_time -
> > > > > >> > >> > >> > > > request/response_queue_time
> > > > > >> > >> > >> > > > > -
> > > > > >> > >> > >> > > > > > > > > > > > remote_time).
> > > > > >> > >> > >> > > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > > I agree with Guozhang that
> > when
> > > a
> > > > > >> user is
> > > > > >> > >> > >> throttled
> > > > > >> > >> > >> > > it
> > > > > >> > >> > >> > > > is
> > > > > >> > >> > >> > > > > > > > likely
> > > > > >> > >> > >> > > > > > > > > > that
> > > > > >> > >> > >> > > > > > > > > > > > we
> > > > > >> > >> > >> > > > > > > > > > > > > > need to see if anything has
> > went
> > > > > wrong
> > > > > >> > >> first,
> > > > > >> > >> > >> and
> > > > > >> > >> > >> > if
> > > > > >> > >> > >> > > > the
> > > > > >> > >> > >> > > > > > > users
> > > > > >> > >> > >> > > > > > > > > are
> > > > > >> > >> > >> > > > > > > > > > > well
> > > > > >> > >> > >> > > > > > > > > > > > > > behaving and just need more
> > > > > >> resources, we
> > > > > >> > >> will
> > > > > >> > >> > >> have
> > > > > >> > >> > >> > > to
> > > > > >> > >> > >> > > > > bump
> > > > > >> > >> > >> > > > > > > up
> > > > > >> > >> > >> > > > > > > > > the
> > > > > >> > >> > >> > > > > > > > > > > > quota
> > > > > >> > >> > >> > > > > > > > > > > > > > for them. It is true that
> > > > > >> pre-allocating
> > > > > >> > >> CPU
> > > > > >> > >> > >> time
> > > > > >> > >> > >> > > quota
> > > > > >> > >> > >> > > > > > > > precisely
> > > > > >> > >> > >> > > > > > > > > > for
> > > > > >> > >> > >> > > > > > > > > > > > the
> > > > > >> > >> > >> > > > > > > > > > > > > > users is difficult. So in
> > > practice
> > > > > it
> > > > > >> > would
> > > > > >> > >> > >> > probably
> > > > > >> > >> > >> > > be
> > > > > >> > >> > >> > > > > > more
> > > > > >> > >> > >> > > > > > > > like
> > > > > >> > >> > >> > > > > > > > > > > first
> > > > > >> > >> > >> > > > > > > > > > > > > set
> > > > > >> > >> > >> > > > > > > > > > > > > > a relative high protective
> CPU
> > > > time
> > > > > >> quota
> > > > > >> > >> for
> > > > > >> > >> > >> > > everyone
> > > > > >> > >> > >> > > > > and
> > > > > >> > >> > >> > > > > > > > > increase
> > > > > >> > >> > >> > > > > > > > > > > > that
> > > > > >> > >> > >> > > > > > > > > > > > > > for some individual clients
> on
> > > > > demand.
> > > > > >> > >> > >> > > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > > Thanks,
> > > > > >> > >> > >> > > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > > Jiangjie (Becket) Qin
> > > > > >> > >> > >> > > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > > On Mon, Feb 20, 2017 at 5:48
> > PM,
> > > > > >> Guozhang
> > > > > >> > >> > Wang <
> > > > > >> > >> > >> > > > > > > > > wangguoz@gmail.com
> > > > > >> > >> > >> > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > wrote:
> > > > > >> > >> > >> > > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > > > This is a great proposal,
> > glad
> > > > to
> > > > > >> see
> > > > > >> > it
> > > > > >> > >> > >> > happening.
> > > > > >> > >> > >> > > > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > > > I am inclined to the CPU
> > > > > >> throttling, or
> > > > > >> > >> more
> > > > > >> > >> > >> > > > > specifically
> > > > > >> > >> > >> > > > > > > > > > > processing
> > > > > >> > >> > >> > > > > > > > > > > > > time
> > > > > >> > >> > >> > > > > > > > > > > > > > > ratio instead of the
> request
> > > > rate
> > > > > >> > >> throttling
> > > > > >> > >> > >> as
> > > > > >> > >> > >> > > well.
> > > > > >> > >> > >> > > > > > > Becket
> > > > > >> > >> > >> > > > > > > > > has
> > > > > >> > >> > >> > > > > > > > > > > very
> > > > > >> > >> > >> > > > > > > > > > > > > > well
> > > > > >> > >> > >> > > > > > > > > > > > > > > summed my rationales
> above,
> > > and
> > > > > one
> > > > > >> > >> thing to
> > > > > >> > >> > >> add
> > > > > >> > >> > >> > > here
> > > > > >> > >> > >> > > > > is
> > > > > >> > >> > >> > > > > > > that
> > > > > >> > >> > >> > > > > > > > > the
> > > > > >> > >> > >> > > > > > > > > > > > > former
> > > > > >> > >> > >> > > > > > > > > > > > > > > has a good support for
> both
> > > > > >> "protecting
> > > > > >> > >> > >> against
> > > > > >> > >> > >> > > rogue
> > > > > >> > >> > >> > > > > > > > clients"
> > > > > >> > >> > >> > > > > > > > > as
> > > > > >> > >> > >> > > > > > > > > > > > well
> > > > > >> > >> > >> > > > > > > > > > > > > as
> > > > > >> > >> > >> > > > > > > > > > > > > > > "utilizing a cluster for
> > > > > >> multi-tenancy
> > > > > >> > >> > usage":
> > > > > >> > >> > >> > when
> > > > > >> > >> > >> > > > > > > thinking
> > > > > >> > >> > >> > > > > > > > > > about
> > > > > >> > >> > >> > > > > > > > > > > > how
> > > > > >> > >> > >> > > > > > > > > > > > > to
> > > > > >> > >> > >> > > > > > > > > > > > > > > explain this to the end
> > > users, I
> > > > > >> find
> > > > > >> > it
> > > > > >> > >> > >> actually
> > > > > >> > >> > >> > > > more
> > > > > >> > >> > >> > > > > > > > natural
> > > > > >> > >> > >> > > > > > > > > > than
> > > > > >> > >> > >> > > > > > > > > > > > the
> > > > > >> > >> > >> > > > > > > > > > > > > > > request rate since as
> > > mentioned
> > > > > >> above,
> > > > > >> > >> > >> different
> > > > > >> > >> > >> > > > > requests
> > > > > >> > >> > >> > > > > > > > will
> > > > > >> > >> > >> > > > > > > > > > have
> > > > > >> > >> > >> > > > > > > > > > > > > quite
> > > > > >> > >> > >> > > > > > > > > > > > > > > different "cost", and
> Kafka
> > > > today
> > > > > >> > already
> > > > > >> > >> > have
> > > > > >> > >> > >> > > > various
> > > > > >> > >> > >> > > > > > > > request
> > > > > >> > >> > >> > > > > > > > > > > types
> > > > > >> > >> > >> > > > > > > > > > > > > > > (produce, fetch, admin,
> > > > metadata,
> > > > > >> etc),
> > > > > >> > >> > >> because
> > > > > >> > >> > >> > of
> > > > > >> > >> > >> > > > that
> > > > > >> > >> > >> > > > > > the
> > > > > >> > >> > >> > > > > > > > > > request
> > > > > >> > >> > >> > > > > > > > > > > > > rate
> > > > > >> > >> > >> > > > > > > > > > > > > > > throttling may not be as
> > > > effective
> > > > > >> > >> unless it
> > > > > >> > >> > >> is
> > > > > >> > >> > >> > set
> > > > > >> > >> > >> > > > > very
> > > > > >> > >> > >> > > > > > > > > > > > > conservatively.
> > > > > >> > >> > >> > > > > > > > > > > > > > >
> > > > > >> > >> > >> > > > > > > > > > > > > > > Regarding to user
> reactions
> > > when
> > > > > >> they
> > > > > >> > are
> > > > > >> > >> > >> > > throttled,
> > > > > >> > >> > >> > > > I
> > > > > >> > >> > >> > > > > > > think
> > > > > >> > >> > >> > > > > > > > it
> > > > > >> > >> > >> > > > > > > > > > may
> > > > > >> > >> > >> > > > > > > > > > > > > > differ
> > > > > >> > >> > >> > > > > > > > > > > > > > > case-by-case, and need to
> be
> > > > > >> > discovered /
> > > > > >> > >> > >> guided
> > > > > >> > >> > >> > by
> > > > > >> > >> > >> > > > > > looking
> > > > > >> > >> > >> > > > > > > > at
> > > > > >> > >> > >> > > > > > > > > > > > relative
> > > > > >> > >> > >> > > > > > > > > > > > > > > metrics. So in other words
> > > users
> > > > > >> would
> > > > > >> > >> not
> > > > > >> > >> > >> expect
> > > > > >> > >> > >> > > to
> > > > > >> > >> > >> > > > > get
> > > > > >> > >> > >> > > > > > > > > > additional
> > > > > >> > >> > >> > > > > > > > > > > > > > > information by simply
> being
> > > told
> > > > > >> "hey,
> > > > > >> > >> you
> > > > > >> > >> > are
> > > > > >> > >> > >> > > > > > throttled",
> > > > > >> > >> > >> > > > > > > > > which
> > > > > >> > >> > >> > > > > > > > > > is
> > > > > >> > >> > >> > > > > > > > > > > > all
> > > > > >> > >> > >> > > > > > > > > > > > > > > what throttling does; they
> > > need
> > > > to
> > > > > >> > take a
> > > > > >> > >> > >> > follow-up
> > > > > >> > >> > >> > > > > step
> > > > > >> > >> > >> > > > > > > and
> > > > > >> > >> > >> > > > > > > > > see
> > > > > >> > >> > >> > > > > > > > > > > > "hmm,
> > > > > >> > >> > >> > > > > > > > > > > > > > I'm
> > > > > >> > >> > >> > > > > > > > > > > > > > > throttled probably because
> > of
> > > > ..",
> > > > > >> > which
> > > > > >> > >> is
> > > > > >> > >> > by
> > > > > >> > >> > >> > > > looking
> > > > > >> > >> > >> > > > > at
> > > > > >> > >> > >> > > > > > > > other
> > > > > >> > >> > >> > > > > > > > > > > > metric
> > > > > >> > >> > >> > > > > > > > > > > > > > > values: e.g. whether I'm
> > > > > bombarding
> > > > > >> the
> > > > > >> > >> > >> brokers
> > > > > >> > >> > >> > > with
> > > > > >> > >> > >> > > > >
> > > > > >>
> > > > > > ...
> > > > > >
> > > > > > [Message clipped]
> > > > >
> > > >
> > >
> >
>

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