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 <rajinisiva...@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.hoo...@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 <j...@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 <
> rajinisiva...@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 <j...@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_Enterprise_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 <
> > > rajinisiva...@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....@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 <
> > wangg...@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 metadata
> > > > > request,
> > > > > > > > which are usually cheap to handle but I'm sending thousands
> per
> > > > > second;
> > > > > > > or
> > > > > > > > is it because I'm catching up and hence sending very heavy
> > > fetching
> > > > > > > request
> > > > > > > > with large min.bytes, etc.
> > > > > > > >
> > > > > > > > Regarding to the implementation, as once discussed with Jun,
> > this
> > > > > seems
> > > > > > > not
> > > > > > > > very difficult since today we are already collecting the
> > "thread
> > > > pool
> > > > > > > > utilization" metrics, which is a single percentage
> > > > > "aggregateIdleMeter"
> > > > > > > > value; but we are already effectively aggregating it for each
> > > > > requests
> > > > > > in
> > > > > > > > KafkaRequestHandler, and we can just extend it by recording
> the
> > > > > source
> > > > > > > > client id when handling them and aggregating by clientId as
> > well
> > > as
> > > > > the
> > > > > > > > total aggregate.
> > > > > > > >
> > > > > > > >
> > > > > > > > Guozhang
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > On Mon, Feb 20, 2017 at 4:27 PM, Jay Kreps <j...@confluent.io
> >
> > > > wrote:
> > > > > > > >
> > > > > > > > > Hey Becket/Rajini,
> > > > > > > > >
> > > > > > > > > When I thought about it more deeply I came around to the
> > > "percent
> > > > > of
> > > > > > > > > processing time" metric too. It seems a lot closer to the
> > thing
> > > > we
> > > > > > > > actually
> > > > > > > > > care about and need to protect. I also think this would be
> a
> > > very
> > > > > > > useful
> > > > > > > > > metric even in the absence of throttling just to debug
> whose
> > > > using
> > > > > > > > > capacity.
> > > > > > > > >
> > > > > > > > > Two problems to consider:
> > > > > > > > >
> > > > > > > > >    1. I agree that for the user it is understandable what
> > lead
> > > to
> > > > > > their
> > > > > > > > >    being throttled, but it is a bit hard to figure out the
> > safe
> > > > > range
> > > > > > > for
> > > > > > > > >    them. i.e. if I have a new app that will send 200
> > > > messages/sec I
> > > > > > can
> > > > > > > > >    probably reason that I'll be under the throttling limit
> of
> > > 300
> > > > > > > > req/sec.
> > > > > > > > >    However if I need to be under a 10% CPU resources limit
> it
> > > may
> > > > > be
> > > > > > a
> > > > > > > > bit
> > > > > > > > >    harder for me to know a priori if i will or won't.
> > > > > > > > >    2. Calculating the available CPU time is a bit difficult
> > > since
> > > > > > there
> > > > > > > > are
> > > > > > > > >    actually two thread pools--the I/O threads and the
> network
> > > > > > threads.
> > > > > > > I
> > > > > > > > > think
> > > > > > > > >    it might be workable to count just the I/O thread time
> as
> > in
> > > > the
> > > > > > > > > proposal,
> > > > > > > > >    but the network thread work is actually non-trivial
> (e.g.
> > > all
> > > > > the
> > > > > > > disk
> > > > > > > > >    reads for fetches happen in that thread). If you count
> > both
> > > > the
> > > > > > > > network
> > > > > > > > > and
> > > > > > > > >    I/O threads it can skew things a bit. E.g. say you have
> 50
> > > > > network
> > > > > > > > > threads,
> > > > > > > > >    10 I/O threads, and 8 cores, what is the available cpu
> > time
> > > > > > > available
> > > > > > > > > in a
> > > > > > > > >    second? I suppose this is a problem whenever you have a
> > > > > bottleneck
> > > > > > > > > between
> > > > > > > > >    I/O and network threads or if you end up significantly
> > > > > > > > over-provisioning
> > > > > > > > >    one pool (both of which are hard to avoid).
> > > > > > > > >
> > > > > > > > > An alternative for CPU throttling would be to use this api:
> > > > > > > > > http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/
> > > > > > > > > management/ThreadMXBean.html#getThreadCpuTime(long)
> > > > > > > > >
> > > > > > > > > That would let you track actual CPU usage across the
> network,
> > > I/O
> > > > > > > > threads,
> > > > > > > > > and purgatory threads and look at it as a percentage of
> total
> > > > > cores.
> > > > > > I
> > > > > > > > > think this fixes many problems in the reliability of the
> > > metric.
> > > > > It's
> > > > > > > > > meaning is slightly different as it is just CPU (you don't
> > get
> > > > > > charged
> > > > > > > > for
> > > > > > > > > time blocking on I/O) but that may be okay because we
> already
> > > > have
> > > > > a
> > > > > > > > > throttle on I/O. The downside is I think it is possible
> this
> > > api
> > > > > can
> > > > > > be
> > > > > > > > > disabled or isn't always available and it may also be
> > expensive
> > > > > (also
> > > > > > > > I've
> > > > > > > > > never used it so not sure if it really works the way i
> > think).
> > > > > > > > >
> > > > > > > > > -Jay
> > > > > > > > >
> > > > > > > > > On Mon, Feb 20, 2017 at 3:17 PM, Becket Qin <
> > > > becket....@gmail.com>
> > > > > > > > wrote:
> > > > > > > > >
> > > > > > > > > > If the purpose of the KIP is only to protect the cluster
> > from
> > > > > being
> > > > > > > > > > overwhelmed by crazy clients and is not intended to
> address
> > > > > > resource
> > > > > > > > > > allocation problem among the clients, I am wondering if
> > using
> > > > > > request
> > > > > > > > > > handling time quota (CPU time quota) is a better option.
> > Here
> > > > are
> > > > > > the
> > > > > > > > > > reasons:
> > > > > > > > > >
> > > > > > > > > > 1. request handling time quota has better protection. Say
> > we
> > > > have
> > > > > > > > request
> > > > > > > > > > rate quota and set that to some value like 100
> > requests/sec,
> > > it
> > > > > is
> > > > > > > > > possible
> > > > > > > > > > that some of the requests are very expensive actually
> take
> > a
> > > > lot
> > > > > of
> > > > > > > > time
> > > > > > > > > to
> > > > > > > > > > handle. In that case a few clients may still occupy a lot
> > of
> > > > CPU
> > > > > > time
> > > > > > > > > even
> > > > > > > > > > the request rate is low. Arguably we can carefully set
> > > request
> > > > > rate
> > > > > > > > quota
> > > > > > > > > > for each request and client id combination, but it could
> > > still
> > > > be
> > > > > > > > tricky
> > > > > > > > > to
> > > > > > > > > > get it right for everyone.
> > > > > > > > > >
> > > > > > > > > > If we use the request time handling quota, we can simply
> > say
> > > no
> > > > > > > clients
> > > > > > > > > can
> > > > > > > > > > take up to more than 30% of the total request handling
> > > capacity
> > > > > > > > (measured
> > > > > > > > > > by time), regardless of the difference among different
> > > requests
> > > > > or
> > > > > > > what
> > > > > > > > > is
> > > > > > > > > > the client doing. In this case maybe we can quota all the
> > > > > requests
> > > > > > if
> > > > > > > > we
> > > > > > > > > > want to.
> > > > > > > > > >
> > > > > > > > > > 2. The main benefit of using request rate limit is that
> it
> > > > seems
> > > > > > more
> > > > > > > > > > intuitive. It is true that it is probably easier to
> explain
> > > to
> > > > > the
> > > > > > > user
> > > > > > > > > > what does that mean. However, in practice it looks the
> > impact
> > > > of
> > > > > > > > request
> > > > > > > > > > rate quota is not more quantifiable than the request
> > handling
> > > > > time
> > > > > > > > quota.
> > > > > > > > > > Unlike the byte rate quota, it is still difficult to
> give a
> > > > > number
> > > > > > > > about
> > > > > > > > > > impact of throughput or latency when a request rate quota
> > is
> > > > hit.
> > > > > > So
> > > > > > > it
> > > > > > > > > is
> > > > > > > > > > not better than the request handling time quota. In fact
> I
> > > feel
> > > > > it
> > > > > > is
> > > > > > > > > > clearer to tell user that "you are limited because you
> have
> > > > taken
> > > > > > 30%
> > > > > > > > of
> > > > > > > > > > the CPU time on the broker" than otherwise something like
> > > "your
> > > > > > > request
> > > > > > > > > > rate quota on metadata request has reached".
> > > > > > > > > >
> > > > > > > > > > Thanks,
> > > > > > > > > >
> > > > > > > > > > Jiangjie (Becket) Qin
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > On Mon, Feb 20, 2017 at 2:23 PM, Jay Kreps <
> > j...@confluent.io
> > > >
> > > > > > wrote:
> > > > > > > > > >
> > > > > > > > > > > I think this proposal makes a lot of sense (especially
> > now
> > > > that
> > > > > > it
> > > > > > > is
> > > > > > > > > > > oriented around request rate) and fills the biggest
> > > remaining
> > > > > gap
> > > > > > > in
> > > > > > > > > the
> > > > > > > > > > > multi-tenancy story.
> > > > > > > > > > >
> > > > > > > > > > > I think for intra-cluster communication (StopReplica,
> > etc)
> > > we
> > > > > > could
> > > > > > > > > avoid
> > > > > > > > > > > throttling entirely. You can secure or otherwise
> > lock-down
> > > > the
> > > > > > > > cluster
> > > > > > > > > > > communication to avoid any unauthorized external party
> > from
> > > > > > trying
> > > > > > > to
> > > > > > > > > > > initiate these requests. As a result we are as likely
> to
> > > > cause
> > > > > > > > problems
> > > > > > > > > > as
> > > > > > > > > > > solve them by throttling these, right?
> > > > > > > > > > >
> > > > > > > > > > > I'm not so sure that we should exempt the consumer
> > requests
> > > > > such
> > > > > > as
> > > > > > > > > > > heartbeat. It's true that if we throttle an app's
> > heartbeat
> > > > > > > requests
> > > > > > > > it
> > > > > > > > > > may
> > > > > > > > > > > cause it to fall out of its consumer group. However if
> we
> > > > don't
> > > > > > > > > throttle
> > > > > > > > > > it
> > > > > > > > > > > it may DDOS the cluster if the heartbeat interval is
> set
> > > > > > > incorrectly
> > > > > > > > or
> > > > > > > > > > if
> > > > > > > > > > > some client in some language has a bug. I think the
> > policy
> > > > with
> > > > > > > this
> > > > > > > > > kind
> > > > > > > > > > > of throttling is to protect the cluster above any
> > > individual
> > > > > app,
> > > > > > > > > right?
> > > > > > > > > > I
> > > > > > > > > > > think in general this should be okay since for most
> > > > deployments
> > > > > > > this
> > > > > > > > > > > setting is meant as more of a safety valve---that is
> > rather
> > > > > than
> > > > > > > set
> > > > > > > > > > > something very close to what you expect to need (say 2
> > > > req/sec
> > > > > or
> > > > > > > > > > whatever)
> > > > > > > > > > > you would have something quite high (like 100 req/sec)
> > with
> > > > > this
> > > > > > > > meant
> > > > > > > > > to
> > > > > > > > > > > prevent a client gone crazy. I think when used this way
> > > > > allowing
> > > > > > > > those
> > > > > > > > > to
> > > > > > > > > > > be throttled would actually provide meaningful
> > protection.
> > > > > > > > > > >
> > > > > > > > > > > -Jay
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > On Fri, Feb 17, 2017 at 9:05 AM, Rajini Sivaram <
> > > > > > > > > rajinisiva...@gmail.com
> > > > > > > > > > >
> > > > > > > > > > > wrote:
> > > > > > > > > > >
> > > > > > > > > > > > Hi all,
> > > > > > > > > > > >
> > > > > > > > > > > > I have just created KIP-124 to introduce request rate
> > > > quotas
> > > > > to
> > > > > > > > > Kafka:
> > > > > > > > > > > >
> > > > > > > > > > > > https://cwiki.apache.org/
> confluence/display/KAFKA/KIP-
> > > > > > > > > > > > 124+-+Request+rate+quotas
> > > > > > > > > > > >
> > > > > > > > > > > > The proposal is for a simple percentage request
> > handling
> > > > time
> > > > > > > quota
> > > > > > > > > > that
> > > > > > > > > > > > can be allocated to *<client-id>*, *<user>* or
> *<user,
> > > > > > > client-id>*.
> > > > > > > > > > There
> > > > > > > > > > > > are a few other suggestions also under "Rejected
> > > > > alternatives".
> > > > > > > > > > Feedback
> > > > > > > > > > > > and suggestions are welcome.
> > > > > > > > > > > >
> > > > > > > > > > > > Thank you...
> > > > > > > > > > > >
> > > > > > > > > > > > Regards,
> > > > > > > > > > > >
> > > > > > > > > > > > Rajini
> > > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > --
> > > > > > > > -- Guozhang
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

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