@Becket 1. Thanks for the comment. You are right that normally there should be just one controller request because of muting, and I had NOT intended to say there would be many enqueued controller requests. I went through the KIP again, and I'm not sure which part conveys that info. I'd be happy to revise if you point it out the section.
2. Though it should not happen in normal conditions, the current design does not preclude multiple controllers running at the same time, hence if we don't have the controller queue capacity config and simply make its capacity to be 1, network threads handling requests from different controllers will be blocked during those troublesome times, which is probably not what we want. On the other hand, adding the extra config with a default value, say 20, guards us from issues in those troublesome times, and IMO there isn't much downside of adding the extra config. @Mayuresh Good catch, this sentence is an obsolete statement based on a previous design. I've revised the wording in the KIP. Thanks, Lucas On Tue, Jul 17, 2018 at 10:33 AM, Mayuresh Gharat < gharatmayures...@gmail.com> wrote: > Hi Lucas, > > Thanks for the KIP. > I am trying to understand why you think "The memory consumption can rise > given the total number of queued requests can go up to 2x" in the impact > section. Normally the requests from controller to a Broker are not high > volume, right ? > > > Thanks, > > Mayuresh > > On Tue, Jul 17, 2018 at 5:06 AM Becket Qin <becket....@gmail.com> wrote: > > > Thanks for the KIP, Lucas. Separating the control plane from the data > plane > > makes a lot of sense. > > > > In the KIP you mentioned that the controller request queue may have many > > requests in it. Will this be a common case? The controller requests still > > goes through the SocketServer. The SocketServer will mute the channel > once > > a request is read and put into the request channel. So assuming there is > > only one connection between controller and each broker, on the broker > side, > > there should be only one controller request in the controller request > queue > > at any given time. If that is the case, do we need a separate controller > > request queue capacity config? The default value 20 means that we expect > > there are 20 controller switches to happen in a short period of time. I > am > > not sure whether someone should increase the controller request queue > > capacity to handle such case, as it seems indicating something very wrong > > has happened. > > > > Thanks, > > > > Jiangjie (Becket) Qin > > > > > > On Fri, Jul 13, 2018 at 1:10 PM, Dong Lin <lindon...@gmail.com> wrote: > > > > > Thanks for the update Lucas. > > > > > > I think the motivation section is intuitive. It will be good to learn > > more > > > about the comments from other reviewers. > > > > > > On Thu, Jul 12, 2018 at 9:48 PM, Lucas Wang <lucasatu...@gmail.com> > > wrote: > > > > > > > Hi Dong, > > > > > > > > I've updated the motivation section of the KIP by explaining the > cases > > > that > > > > would have user impacts. > > > > Please take a look at let me know your comments. > > > > > > > > Thanks, > > > > Lucas > > > > > > > > On Mon, Jul 9, 2018 at 5:53 PM, Lucas Wang <lucasatu...@gmail.com> > > > wrote: > > > > > > > > > Hi Dong, > > > > > > > > > > The simulation of disk being slow is merely for me to easily > > construct > > > a > > > > > testing scenario > > > > > with a backlog of produce requests. In production, other than the > > disk > > > > > being slow, a backlog of > > > > > produce requests may also be caused by high produce QPS. > > > > > In that case, we may not want to kill the broker and that's when > this > > > KIP > > > > > can be useful, both for JBOD > > > > > and non-JBOD setup. > > > > > > > > > > Going back to your previous question about each ProduceRequest > > covering > > > > 20 > > > > > partitions that are randomly > > > > > distributed, let's say a LeaderAndIsr request is enqueued that > tries > > to > > > > > switch the current broker, say broker0, from leader to follower > > > > > *for one of the partitions*, say *test-0*. For the sake of > argument, > > > > > let's also assume the other brokers, say broker1, have *stopped* > > > fetching > > > > > from > > > > > the current broker, i.e. broker0. > > > > > 1. If the enqueued produce requests have acks = -1 (ALL) > > > > > 1.1 without this KIP, the ProduceRequests ahead of LeaderAndISR > > will > > > be > > > > > put into the purgatory, > > > > > and since they'll never be replicated to other brokers > > (because > > > > of > > > > > the assumption made above), they will > > > > > be completed either when the LeaderAndISR request is > > processed > > > or > > > > > when the timeout happens. > > > > > 1.2 With this KIP, broker0 will immediately transition the > > partition > > > > > test-0 to become a follower, > > > > > after the current broker sees the replication of the > > remaining > > > 19 > > > > > partitions, it can send a response indicating that > > > > > it's no longer the leader for the "test-0". > > > > > To see the latency difference between 1.1 and 1.2, let's say > there > > > are > > > > > 24K produce requests ahead of the LeaderAndISR, and there are 8 io > > > > threads, > > > > > so each io thread will process approximately 3000 produce > requests. > > > Now > > > > > let's investigate the io thread that finally processed the > > > LeaderAndISR. > > > > > For the 3000 produce requests, if we model the time when their > > > > remaining > > > > > 19 partitions catch up as t0, t1, ...t2999, and the LeaderAndISR > > > request > > > > is > > > > > processed at time t3000. > > > > > Without this KIP, the 1st produce request would have waited an > > extra > > > > > t3000 - t0 time in the purgatory, the 2nd an extra time of t3000 - > > t1, > > > > etc. > > > > > Roughly speaking, the latency difference is bigger for the > earlier > > > > > produce requests than for the later ones. For the same reason, the > > more > > > > > ProduceRequests queued > > > > > before the LeaderAndISR, the bigger benefit we get (capped by the > > > > > produce timeout). > > > > > 2. If the enqueued produce requests have acks=0 or acks=1 > > > > > There will be no latency differences in this case, but > > > > > 2.1 without this KIP, the records of partition test-0 in the > > > > > ProduceRequests ahead of the LeaderAndISR will be appended to the > > local > > > > log, > > > > > and eventually be truncated after processing the > > LeaderAndISR. > > > > > This is what's referred to as > > > > > "some unofficial definition of data loss in terms of > messages > > > > > beyond the high watermark". > > > > > 2.2 with this KIP, we can mitigate the effect since if the > > > LeaderAndISR > > > > > is immediately processed, the response to producers will have > > > > > the NotLeaderForPartition error, causing producers to retry > > > > > > > > > > This explanation above is the benefit for reducing the latency of a > > > > broker > > > > > becoming the follower, > > > > > closely related is reducing the latency of a broker becoming the > > > leader. > > > > > In this case, the benefit is even more obvious, if other brokers > have > > > > > resigned leadership, and the > > > > > current broker should take leadership. Any delay in processing the > > > > > LeaderAndISR will be perceived > > > > > by clients as unavailability. In extreme cases, this can cause > failed > > > > > produce requests if the retries are > > > > > exhausted. > > > > > > > > > > Another two types of controller requests are UpdateMetadata and > > > > > StopReplica, which I'll briefly discuss as follows: > > > > > For UpdateMetadata requests, delayed processing means clients > > receiving > > > > > stale metadata, e.g. with the wrong leadership info > > > > > for certain partitions, and the effect is more retries or even > fatal > > > > > failure if the retries are exhausted. > > > > > > > > > > For StopReplica requests, a long queuing time may degrade the > > > performance > > > > > of topic deletion. > > > > > > > > > > Regarding your last question of the delay for > DescribeLogDirsRequest, > > > you > > > > > are right > > > > > that this KIP cannot help with the latency in getting the log dirs > > > info, > > > > > and it's only relevant > > > > > when controller requests are involved. > > > > > > > > > > Regards, > > > > > Lucas > > > > > > > > > > > > > > > On Tue, Jul 3, 2018 at 5:11 PM, Dong Lin <lindon...@gmail.com> > > wrote: > > > > > > > > > >> Hey Jun, > > > > >> > > > > >> Thanks much for the comments. It is good point. So the feature may > > be > > > > >> useful for JBOD use-case. I have one question below. > > > > >> > > > > >> Hey Lucas, > > > > >> > > > > >> Do you think this feature is also useful for non-JBOD setup or it > is > > > > only > > > > >> useful for the JBOD setup? It may be useful to understand this. > > > > >> > > > > >> When the broker is setup using JBOD, in order to move leaders on > the > > > > >> failed > > > > >> disk to other disks, the system operator first needs to get the > list > > > of > > > > >> partitions on the failed disk. This is currently achieved using > > > > >> AdminClient.describeLogDirs(), which sends DescribeLogDirsRequest > to > > > the > > > > >> broker. If we only prioritize the controller requests, then the > > > > >> DescribeLogDirsRequest > > > > >> may still take a long time to be processed by the broker. So the > > > overall > > > > >> time to move leaders away from the failed disk may still be long > > even > > > > with > > > > >> this KIP. What do you think? > > > > >> > > > > >> Thanks, > > > > >> Dong > > > > >> > > > > >> > > > > >> On Tue, Jul 3, 2018 at 4:38 PM, Lucas Wang <lucasatu...@gmail.com > > > > > > wrote: > > > > >> > > > > >> > Thanks for the insightful comment, Jun. > > > > >> > > > > > >> > @Dong, > > > > >> > Since both of the two comments in your previous email are about > > the > > > > >> > benefits of this KIP and whether it's useful, > > > > >> > in light of Jun's last comment, do you agree that this KIP can > be > > > > >> > beneficial in the case mentioned by Jun? > > > > >> > Please let me know, thanks! > > > > >> > > > > > >> > Regards, > > > > >> > Lucas > > > > >> > > > > > >> > On Tue, Jul 3, 2018 at 2:07 PM, Jun Rao <j...@confluent.io> > wrote: > > > > >> > > > > > >> > > Hi, Lucas, Dong, > > > > >> > > > > > > >> > > If all disks on a broker are slow, one probably should just > kill > > > the > > > > >> > > broker. In that case, this KIP may not help. If only one of > the > > > > disks > > > > >> on > > > > >> > a > > > > >> > > broker is slow, one may want to fail that disk and move the > > > leaders > > > > on > > > > >> > that > > > > >> > > disk to other brokers. In that case, being able to process the > > > > >> > LeaderAndIsr > > > > >> > > requests faster will potentially help the producers recover > > > quicker. > > > > >> > > > > > > >> > > Thanks, > > > > >> > > > > > > >> > > Jun > > > > >> > > > > > > >> > > On Mon, Jul 2, 2018 at 7:56 PM, Dong Lin <lindon...@gmail.com > > > > > > wrote: > > > > >> > > > > > > >> > > > Hey Lucas, > > > > >> > > > > > > > >> > > > Thanks for the reply. Some follow up questions below. > > > > >> > > > > > > > >> > > > Regarding 1, if each ProduceRequest covers 20 partitions > that > > > are > > > > >> > > randomly > > > > >> > > > distributed across all partitions, then each ProduceRequest > > will > > > > >> likely > > > > >> > > > cover some partitions for which the broker is still leader > > after > > > > it > > > > >> > > quickly > > > > >> > > > processes the > > > > >> > > > LeaderAndIsrRequest. Then broker will still be slow in > > > processing > > > > >> these > > > > >> > > > ProduceRequest and request will still be very high with this > > > KIP. > > > > It > > > > >> > > seems > > > > >> > > > that most ProduceRequest will still timeout after 30 > seconds. > > Is > > > > >> this > > > > >> > > > understanding correct? > > > > >> > > > > > > > >> > > > Regarding 2, if most ProduceRequest will still timeout after > > 30 > > > > >> > seconds, > > > > >> > > > then it is less clear how this KIP reduces average produce > > > > latency. > > > > >> Can > > > > >> > > you > > > > >> > > > clarify what metrics can be improved by this KIP? > > > > >> > > > > > > > >> > > > Not sure why system operator directly cares number of > > truncated > > > > >> > messages. > > > > >> > > > Do you mean this KIP can improve average throughput or > reduce > > > > >> message > > > > >> > > > duplication? It will be good to understand this. > > > > >> > > > > > > > >> > > > Thanks, > > > > >> > > > Dong > > > > >> > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > On Tue, 3 Jul 2018 at 7:12 AM Lucas Wang < > > lucasatu...@gmail.com > > > > > > > > >> > wrote: > > > > >> > > > > > > > >> > > > > Hi Dong, > > > > >> > > > > > > > > >> > > > > Thanks for your valuable comments. Please see my reply > > below. > > > > >> > > > > > > > > >> > > > > 1. The Google doc showed only 1 partition. Now let's > > consider > > > a > > > > >> more > > > > >> > > > common > > > > >> > > > > scenario > > > > >> > > > > where broker0 is the leader of many partitions. And let's > > say > > > > for > > > > >> > some > > > > >> > > > > reason its IO becomes slow. > > > > >> > > > > The number of leader partitions on broker0 is so large, > say > > > 10K, > > > > >> that > > > > >> > > the > > > > >> > > > > cluster is skewed, > > > > >> > > > > and the operator would like to shift the leadership for a > > lot > > > of > > > > >> > > > > partitions, say 9K, to other brokers, > > > > >> > > > > either manually or through some service like cruise > control. > > > > >> > > > > With this KIP, not only will the leadership transitions > > finish > > > > >> more > > > > >> > > > > quickly, helping the cluster itself becoming more > balanced, > > > > >> > > > > but all existing producers corresponding to the 9K > > partitions > > > > will > > > > >> > get > > > > >> > > > the > > > > >> > > > > errors relatively quickly > > > > >> > > > > rather than relying on their timeout, thanks to the > batched > > > > async > > > > >> ZK > > > > >> > > > > operations. > > > > >> > > > > To me it's a useful feature to have during such > troublesome > > > > times. > > > > >> > > > > > > > > >> > > > > > > > > >> > > > > 2. The experiments in the Google Doc have shown that with > > this > > > > KIP > > > > >> > many > > > > >> > > > > producers > > > > >> > > > > receive an explicit error NotLeaderForPartition, based on > > > which > > > > >> they > > > > >> > > > retry > > > > >> > > > > immediately. > > > > >> > > > > Therefore the latency (~14 seconds+quick retry) for their > > > single > > > > >> > > message > > > > >> > > > is > > > > >> > > > > much smaller > > > > >> > > > > compared with the case of timing out without the KIP (30 > > > seconds > > > > >> for > > > > >> > > > timing > > > > >> > > > > out + quick retry). > > > > >> > > > > One might argue that reducing the timing out on the > producer > > > > side > > > > >> can > > > > >> > > > > achieve the same result, > > > > >> > > > > yet reducing the timeout has its own drawbacks[1]. > > > > >> > > > > > > > > >> > > > > Also *IF* there were a metric to show the number of > > truncated > > > > >> > messages > > > > >> > > on > > > > >> > > > > brokers, > > > > >> > > > > with the experiments done in the Google Doc, it should be > > easy > > > > to > > > > >> see > > > > >> > > > that > > > > >> > > > > a lot fewer messages need > > > > >> > > > > to be truncated on broker0 since the up-to-date metadata > > > avoids > > > > >> > > appending > > > > >> > > > > of messages > > > > >> > > > > in subsequent PRODUCE requests. If we talk to a system > > > operator > > > > >> and > > > > >> > ask > > > > >> > > > > whether > > > > >> > > > > they prefer fewer wasteful IOs, I bet most likely the > answer > > > is > > > > >> yes. > > > > >> > > > > > > > > >> > > > > 3. To answer your question, I think it might be helpful to > > > > >> construct > > > > >> > > some > > > > >> > > > > formulas. > > > > >> > > > > To simplify the modeling, I'm going back to the case where > > > there > > > > >> is > > > > >> > > only > > > > >> > > > > ONE partition involved. > > > > >> > > > > Following the experiments in the Google Doc, let's say > > broker0 > > > > >> > becomes > > > > >> > > > the > > > > >> > > > > follower at time t0, > > > > >> > > > > and after t0 there were still N produce requests in its > > > request > > > > >> > queue. > > > > >> > > > > With the up-to-date metadata brought by this KIP, broker0 > > can > > > > >> reply > > > > >> > > with > > > > >> > > > an > > > > >> > > > > NotLeaderForPartition exception, > > > > >> > > > > let's use M1 to denote the average processing time of > > replying > > > > >> with > > > > >> > > such > > > > >> > > > an > > > > >> > > > > error message. > > > > >> > > > > Without this KIP, the broker will need to append messages > to > > > > >> > segments, > > > > >> > > > > which may trigger a flush to disk, > > > > >> > > > > let's use M2 to denote the average processing time for > such > > > > logic. > > > > >> > > > > Then the average extra latency incurred without this KIP > is > > N > > > * > > > > >> (M2 - > > > > >> > > > M1) / > > > > >> > > > > 2. > > > > >> > > > > > > > > >> > > > > In practice, M2 should always be larger than M1, which > means > > > as > > > > >> long > > > > >> > > as N > > > > >> > > > > is positive, > > > > >> > > > > we would see improvements on the average latency. > > > > >> > > > > There does not need to be significant backlog of requests > in > > > the > > > > >> > > request > > > > >> > > > > queue, > > > > >> > > > > or severe degradation of disk performance to have the > > > > improvement. > > > > >> > > > > > > > > >> > > > > Regards, > > > > >> > > > > Lucas > > > > >> > > > > > > > > >> > > > > > > > > >> > > > > [1] For instance, reducing the timeout on the producer > side > > > can > > > > >> > trigger > > > > >> > > > > unnecessary duplicate requests > > > > >> > > > > when the corresponding leader broker is overloaded, > > > exacerbating > > > > >> the > > > > >> > > > > situation. > > > > >> > > > > > > > > >> > > > > On Sun, Jul 1, 2018 at 9:18 PM, Dong Lin < > > lindon...@gmail.com > > > > > > > > >> > wrote: > > > > >> > > > > > > > > >> > > > > > Hey Lucas, > > > > >> > > > > > > > > > >> > > > > > Thanks much for the detailed documentation of the > > > experiment. > > > > >> > > > > > > > > > >> > > > > > Initially I also think having a separate queue for > > > controller > > > > >> > > requests > > > > >> > > > is > > > > >> > > > > > useful because, as you mentioned in the summary section > of > > > the > > > > >> > Google > > > > >> > > > > doc, > > > > >> > > > > > controller requests are generally more important than > data > > > > >> requests > > > > >> > > and > > > > >> > > > > we > > > > >> > > > > > probably want controller requests to be processed > sooner. > > > But > > > > >> then > > > > >> > > Eno > > > > >> > > > > has > > > > >> > > > > > two very good questions which I am not sure the Google > doc > > > has > > > > >> > > answered > > > > >> > > > > > explicitly. Could you help with the following questions? > > > > >> > > > > > > > > > >> > > > > > 1) It is not very clear what is the actual benefit of > > > KIP-291 > > > > to > > > > >> > > users. > > > > >> > > > > The > > > > >> > > > > > experiment setup in the Google doc simulates the > scenario > > > that > > > > >> > broker > > > > >> > > > is > > > > >> > > > > > very slow handling ProduceRequest due to e.g. slow disk. > > It > > > > >> > currently > > > > >> > > > > > assumes that there is only 1 partition. But in the > common > > > > >> scenario, > > > > >> > > it > > > > >> > > > is > > > > >> > > > > > probably reasonable to assume that there are many other > > > > >> partitions > > > > >> > > that > > > > >> > > > > are > > > > >> > > > > > also actively produced to and ProduceRequest to these > > > > partition > > > > >> > also > > > > >> > > > > takes > > > > >> > > > > > e.g. 2 seconds to be processed. So even if broker0 can > > > become > > > > >> > > follower > > > > >> > > > > for > > > > >> > > > > > the partition 0 soon, it probably still needs to process > > the > > > > >> > > > > ProduceRequest > > > > >> > > > > > slowly t in the queue because these ProduceRequests > cover > > > > other > > > > >> > > > > partitions. > > > > >> > > > > > Thus most ProduceRequest will still timeout after 30 > > seconds > > > > and > > > > >> > most > > > > >> > > > > > clients will still likely timeout after 30 seconds. Then > > it > > > is > > > > >> not > > > > >> > > > > > obviously what is the benefit to client since client > will > > > > >> timeout > > > > >> > > after > > > > >> > > > > 30 > > > > >> > > > > > seconds before possibly re-connecting to broker1, with > or > > > > >> without > > > > >> > > > > KIP-291. > > > > >> > > > > > Did I miss something here? > > > > >> > > > > > > > > > >> > > > > > 2) I guess Eno's is asking for the specific benefits of > > this > > > > >> KIP to > > > > >> > > > user > > > > >> > > > > or > > > > >> > > > > > system administrator, e.g. whether this KIP decreases > > > average > > > > >> > > latency, > > > > >> > > > > > 999th percentile latency, probably of exception exposed > to > > > > >> client > > > > >> > > etc. > > > > >> > > > It > > > > >> > > > > > is probably useful to clarify this. > > > > >> > > > > > > > > > >> > > > > > 3) Does this KIP help improve user experience only when > > > there > > > > is > > > > >> > > issue > > > > >> > > > > with > > > > >> > > > > > broker, e.g. significant backlog in the request queue > due > > to > > > > >> slow > > > > >> > > disk > > > > >> > > > as > > > > >> > > > > > described in the Google doc? Or is this KIP also useful > > when > > > > >> there > > > > >> > is > > > > >> > > > no > > > > >> > > > > > ongoing issue in the cluster? It might be helpful to > > clarify > > > > >> this > > > > >> > to > > > > >> > > > > > understand the benefit of this KIP. > > > > >> > > > > > > > > > >> > > > > > > > > > >> > > > > > Thanks much, > > > > >> > > > > > Dong > > > > >> > > > > > > > > > >> > > > > > > > > > >> > > > > > > > > > >> > > > > > > > > > >> > > > > > On Fri, Jun 29, 2018 at 2:58 PM, Lucas Wang < > > > > >> lucasatu...@gmail.com > > > > >> > > > > > > >> > > > > wrote: > > > > >> > > > > > > > > > >> > > > > > > Hi Eno, > > > > >> > > > > > > > > > > >> > > > > > > Sorry for the delay in getting the experiment results. > > > > >> > > > > > > Here is a link to the positive impact achieved by > > > > implementing > > > > >> > the > > > > >> > > > > > proposed > > > > >> > > > > > > change: > > > > >> > > > > > > https://docs.google.com/document/d/ > > > > 1ge2jjp5aPTBber6zaIT9AdhW > > > > >> > > > > > > FWUENJ3JO6Zyu4f9tgQ/edit?usp=sharing > > > > >> > > > > > > Please take a look when you have time and let me know > > your > > > > >> > > feedback. > > > > >> > > > > > > > > > > >> > > > > > > Regards, > > > > >> > > > > > > Lucas > > > > >> > > > > > > > > > > >> > > > > > > On Tue, Jun 26, 2018 at 9:52 AM, Harsha < > > ka...@harsha.io> > > > > >> wrote: > > > > >> > > > > > > > > > > >> > > > > > > > Thanks for the pointer. Will take a look might suit > > our > > > > >> > > > requirements > > > > >> > > > > > > > better. > > > > >> > > > > > > > > > > > >> > > > > > > > Thanks, > > > > >> > > > > > > > Harsha > > > > >> > > > > > > > > > > > >> > > > > > > > On Mon, Jun 25th, 2018 at 2:52 PM, Lucas Wang < > > > > >> > > > lucasatu...@gmail.com > > > > >> > > > > > > > > > >> > > > > > > > wrote: > > > > >> > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > Hi Harsha, > > > > >> > > > > > > > > > > > > >> > > > > > > > > If I understand correctly, the replication quota > > > > mechanism > > > > >> > > > proposed > > > > >> > > > > > in > > > > >> > > > > > > > > KIP-73 can be helpful in that scenario. > > > > >> > > > > > > > > Have you tried it out? > > > > >> > > > > > > > > > > > > >> > > > > > > > > Thanks, > > > > >> > > > > > > > > Lucas > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > On Sun, Jun 24, 2018 at 8:28 AM, Harsha < > > > > ka...@harsha.io > > > > >> > > > > > >> > > > wrote: > > > > >> > > > > > > > > > > > > >> > > > > > > > > > Hi Lucas, > > > > >> > > > > > > > > > One more question, any thoughts on making this > > > > >> configurable > > > > >> > > > > > > > > > and also allowing subset of data requests to be > > > > >> > prioritized. > > > > >> > > > For > > > > >> > > > > > > > example > > > > >> > > > > > > > > > > > > >> > > > > > > > > > ,we notice in our cluster when we take out a > > broker > > > > and > > > > >> > bring > > > > >> > > > new > > > > >> > > > > > one > > > > >> > > > > > > > it > > > > >> > > > > > > > > > > > > >> > > > > > > > > > will try to become follower and have lot of > fetch > > > > >> requests > > > > >> > to > > > > >> > > > > other > > > > >> > > > > > > > > leaders > > > > >> > > > > > > > > > in clusters. This will negatively effect the > > > > >> > > application/client > > > > >> > > > > > > > > requests. > > > > >> > > > > > > > > > We are also exploring the similar solution to > > > > >> de-prioritize > > > > >> > > if > > > > >> > > > a > > > > >> > > > > > new > > > > >> > > > > > > > > > replica comes in for fetch requests, we are ok > > with > > > > the > > > > >> > > replica > > > > >> > > > > to > > > > >> > > > > > be > > > > >> > > > > > > > > > taking time but the leaders should prioritize > the > > > > client > > > > >> > > > > requests. > > > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > > Thanks, > > > > >> > > > > > > > > > Harsha > > > > >> > > > > > > > > > > > > > >> > > > > > > > > > On Fri, Jun 22nd, 2018 at 11:35 AM Lucas Wang > > wrote: > > > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > Hi Eno, > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > Sorry for the delayed response. > > > > >> > > > > > > > > > > - I haven't implemented the feature yet, so no > > > > >> > experimental > > > > >> > > > > > results > > > > >> > > > > > > > so > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > far. > > > > >> > > > > > > > > > > And I plan to test in out in the following > days. > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > - You are absolutely right that the priority > > queue > > > > >> does > > > > >> > not > > > > >> > > > > > > > completely > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > prevent > > > > >> > > > > > > > > > > data requests being processed ahead of > > controller > > > > >> > requests. > > > > >> > > > > > > > > > > That being said, I expect it to greatly > mitigate > > > the > > > > >> > effect > > > > >> > > > of > > > > >> > > > > > > stable > > > > >> > > > > > > > > > > metadata. > > > > >> > > > > > > > > > > In any case, I'll try it out and post the > > results > > > > >> when I > > > > >> > > have > > > > >> > > > > it. > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > Regards, > > > > >> > > > > > > > > > > Lucas > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > On Wed, Jun 20, 2018 at 5:44 AM, Eno Thereska > < > > > > >> > > > > > > > eno.there...@gmail.com > > > > >> > > > > > > > > > > > > > >> > > > > > > > > > > wrote: > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > Hi Lucas, > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > > Sorry for the delay, just had a look at > this. > > A > > > > >> couple > > > > >> > of > > > > >> > > > > > > > questions: > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > - did you notice any positive change after > > > > >> implementing > > > > >> > > > this > > > > >> > > > > > KIP? > > > > >> > > > > > > > > I'm > > > > >> > > > > > > > > > > > wondering if you have any experimental > results > > > > that > > > > >> > show > > > > >> > > > the > > > > >> > > > > > > > benefit > > > > >> > > > > > > > > of > > > > >> > > > > > > > > > > the > > > > >> > > > > > > > > > > > two queues. > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > > - priority is usually not sufficient in > > > addressing > > > > >> the > > > > >> > > > > problem > > > > >> > > > > > > the > > > > >> > > > > > > > > KIP > > > > >> > > > > > > > > > > > identifies. Even with priority queues, you > > will > > > > >> > sometimes > > > > >> > > > > > > (often?) > > > > >> > > > > > > > > have > > > > >> > > > > > > > > > > the > > > > >> > > > > > > > > > > > case that data plane requests will be ahead > of > > > the > > > > >> > > control > > > > >> > > > > > plane > > > > >> > > > > > > > > > > requests. > > > > >> > > > > > > > > > > > This happens because the system might have > > > already > > > > >> > > started > > > > >> > > > > > > > > processing > > > > >> > > > > > > > > > > the > > > > >> > > > > > > > > > > > data plane requests before the control plane > > > ones > > > > >> > > arrived. > > > > >> > > > So > > > > >> > > > > > it > > > > >> > > > > > > > > would > > > > >> > > > > > > > > > > be > > > > >> > > > > > > > > > > > good to know what % of the problem this KIP > > > > >> addresses. > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > > Thanks > > > > >> > > > > > > > > > > > Eno > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > On Fri, Jun 15, 2018 at 4:44 PM, Ted Yu < > > > > >> > > > > yuzhih...@gmail.com > > > > >> > > > > > > > > > > >> > > > > > > > > wrote: > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > > > Change looks good. > > > > >> > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > Thanks > > > > >> > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > On Fri, Jun 15, 2018 at 8:42 AM, Lucas > Wang > > < > > > > >> > > > > > > > lucasatu...@gmail.com > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > wrote: > > > > >> > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > Hi Ted, > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > Thanks for the suggestion. I've updated > > the > > > > KIP. > > > > >> > > Please > > > > >> > > > > > take > > > > >> > > > > > > > > > another > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > look. > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > Lucas > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > On Thu, Jun 14, 2018 at 6:34 PM, Ted Yu > < > > > > >> > > > > > > yuzhih...@gmail.com > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > wrote: > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > Currently in KafkaConfig.scala : > > > > >> > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > val QueuedMaxRequests = 500 > > > > >> > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > It would be good if you can include > the > > > > >> default > > > > >> > > value > > > > >> > > > > for > > > > >> > > > > > > > this > > > > >> > > > > > > > > > > > > >> > > > > > > > > > new > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > config > > > > >> > > > > > > > > > > > > > > in the KIP. > > > > >> > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > Thanks > > > > >> > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > On Thu, Jun 14, 2018 at 4:28 PM, Lucas > > > Wang > > > > < > > > > >> > > > > > > > > > lucasatu...@gmail.com > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > wrote: > > > > >> > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > Hi Ted, Dong > > > > >> > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > I've updated the KIP by adding a new > > > > config, > > > > >> > > > instead > > > > >> > > > > of > > > > >> > > > > > > > > reusing > > > > >> > > > > > > > > > > the > > > > >> > > > > > > > > > > > > > > > existing one. > > > > >> > > > > > > > > > > > > > > > Please take another look when you > have > > > > time. > > > > >> > > > Thanks a > > > > >> > > > > > > lot! > > > > >> > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > Lucas > > > > >> > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > On Thu, Jun 14, 2018 at 2:33 PM, Ted > > Yu > > > < > > > > >> > > > > > > > yuzhih...@gmail.com > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > wrote: > > > > >> > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > bq. that's a waste of resource if > > > > control > > > > >> > > request > > > > >> > > > > > rate > > > > >> > > > > > > is > > > > >> > > > > > > > > low > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > I don't know if control request > rate > > > can > > > > >> get > > > > >> > to > > > > >> > > > > > > 100,000, > > > > >> > > > > > > > > > > likely > > > > >> > > > > > > > > > > > > not. > > > > >> > > > > > > > > > > > > > > Then > > > > >> > > > > > > > > > > > > > > > > using the same bound as that for > > data > > > > >> > requests > > > > >> > > > > seems > > > > >> > > > > > > > high. > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > On Wed, Jun 13, 2018 at 10:13 PM, > > > Lucas > > > > >> Wang > > > > >> > < > > > > >> > > > > > > > > > > > > lucasatu...@gmail.com > > > > > >> > > > > > > > > > > > > > > > > wrote: > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > Hi Ted, > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > Thanks for taking a look at this > > > KIP. > > > > >> > > > > > > > > > > > > > > > > > Let's say today the setting of > > > > >> > > > > > "queued.max.requests" > > > > >> > > > > > > in > > > > >> > > > > > > > > > > > cluster A > > > > >> > > > > > > > > > > > > > is > > > > >> > > > > > > > > > > > > > > > > 1000, > > > > >> > > > > > > > > > > > > > > > > > while the setting in cluster B > is > > > > >> 100,000. > > > > >> > > > > > > > > > > > > > > > > > The 100 times difference might > > have > > > > >> > indicated > > > > >> > > > > that > > > > >> > > > > > > > > machines > > > > >> > > > > > > > > > > in > > > > >> > > > > > > > > > > > > > > cluster > > > > >> > > > > > > > > > > > > > > > B > > > > >> > > > > > > > > > > > > > > > > > have larger memory. > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > By reusing the > > > "queued.max.requests", > > > > >> the > > > > >> > > > > > > > > > > controlRequestQueue > > > > >> > > > > > > > > > > > in > > > > >> > > > > > > > > > > > > > > > cluster > > > > >> > > > > > > > > > > > > > > > > B > > > > >> > > > > > > > > > > > > > > > > > automatically > > > > >> > > > > > > > > > > > > > > > > > gets a 100x capacity without > > > > explicitly > > > > >> > > > bothering > > > > >> > > > > > the > > > > >> > > > > > > > > > > > operators. > > > > >> > > > > > > > > > > > > > > > > > I understand the counter > argument > > > can > > > > be > > > > >> > that > > > > >> > > > > maybe > > > > >> > > > > > > > > that's > > > > >> > > > > > > > > > a > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > waste > > > > >> > > > > > > > > > > > > > of > > > > >> > > > > > > > > > > > > > > > > > resource if control request > > > > >> > > > > > > > > > > > > > > > > > rate is low and operators may > want > > > to > > > > >> fine > > > > >> > > tune > > > > >> > > > > the > > > > >> > > > > > > > > > capacity > > > > >> > > > > > > > > > > of > > > > >> > > > > > > > > > > > > the > > > > >> > > > > > > > > > > > > > > > > > controlRequestQueue. > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > I'm ok with either approach, and > > can > > > > >> change > > > > >> > > it > > > > >> > > > if > > > > >> > > > > > you > > > > >> > > > > > > > or > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > anyone > > > > >> > > > > > > > > > > > > > else > > > > >> > > > > > > > > > > > > > > > > feels > > > > >> > > > > > > > > > > > > > > > > > strong about adding the extra > > > config. > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > Thanks, > > > > >> > > > > > > > > > > > > > > > > > Lucas > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > On Wed, Jun 13, 2018 at 3:11 PM, > > Ted > > > > Yu > > > > >> < > > > > >> > > > > > > > > > yuzhih...@gmail.com > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > wrote: > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > Lucas: > > > > >> > > > > > > > > > > > > > > > > > > Under Rejected Alternatives, > #2, > > > can > > > > >> you > > > > >> > > > > > elaborate > > > > >> > > > > > > a > > > > >> > > > > > > > > bit > > > > >> > > > > > > > > > > more > > > > >> > > > > > > > > > > > > on > > > > >> > > > > > > > > > > > > > > why > > > > >> > > > > > > > > > > > > > > > > the > > > > >> > > > > > > > > > > > > > > > > > > separate config has bigger > > impact > > > ? > > > > >> > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > Thanks > > > > >> > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > On Wed, Jun 13, 2018 at 2:00 > PM, > > > > Dong > > > > >> > Lin < > > > > >> > > > > > > > > > > > lindon...@gmail.com > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > wrote: > > > > >> > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > Hey Luca, > > > > >> > > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > Thanks for the KIP. Looks > good > > > > >> overall. > > > > >> > > > Some > > > > >> > > > > > > > > comments > > > > >> > > > > > > > > > > > below: > > > > >> > > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > - We usually specify the > full > > > > mbean > > > > >> for > > > > >> > > the > > > > >> > > > > new > > > > >> > > > > > > > > metrics > > > > >> > > > > > > > > > > in > > > > >> > > > > > > > > > > > > the > > > > >> > > > > > > > > > > > > > > KIP. > > > > >> > > > > > > > > > > > > > > > > Can > > > > >> > > > > > > > > > > > > > > > > > > you > > > > >> > > > > > > > > > > > > > > > > > > > specify it in the Public > > > Interface > > > > >> > > section > > > > >> > > > > > > similar > > > > >> > > > > > > > > to > > > > >> > > > > > > > > > > > KIP-237 > > > > >> > > > > > > > > > > > > > > > > > > > < https://cwiki.apache.org/ > > > > >> > > > > > > > > > confluence/display/KAFKA/KIP- > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > 237%3A+More+Controller+Health+ > > > > >> Metrics> > > > > >> > > > > > > > > > > > > > > > > > > > ? > > > > >> > > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > - Maybe we could follow the > > same > > > > >> > pattern > > > > >> > > as > > > > >> > > > > > > KIP-153 > > > > >> > > > > > > > > > > > > > > > > > > > < https://cwiki.apache.org/ > > > > >> > > > > > > > > > confluence/display/KAFKA/KIP- > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > 153%3A+Include+only+client+traffic+in+BytesOutPerSec+ > > > > >> > > > > > > > > > > > > metric>, > > > > >> > > > > > > > > > > > > > > > > > > > where we keep the existing > > > sensor > > > > >> name > > > > >> > > > > > > > > "BytesInPerSec" > > > > >> > > > > > > > > > > and > > > > >> > > > > > > > > > > > > add > > > > >> > > > > > > > > > > > > > a > > > > >> > > > > > > > > > > > > > > > new > > > > >> > > > > > > > > > > > > > > > > > > sensor > > > > >> > > > > > > > > > > > > > > > > > > > "ReplicationBytesInPerSec", > > > rather > > > > >> than > > > > >> > > > > > replacing > > > > >> > > > > > > > > the > > > > >> > > > > > > > > > > > sensor > > > > >> > > > > > > > > > > > > > > name " > > > > >> > > > > > > > > > > > > > > > > > > > BytesInPerSec" with e.g. > > > > >> > > > > "ClientBytesInPerSec". > > > > >> > > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > - It seems that the KIP > > changes > > > > the > > > > >> > > > semantics > > > > >> > > > > > of > > > > >> > > > > > > > the > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > broker > > > > >> > > > > > > > > > > > > > > config > > > > >> > > > > > > > > > > > > > > > > > > > "queued.max.requests" > because > > > the > > > > >> > number > > > > >> > > of > > > > >> > > > > > total > > > > >> > > > > > > > > > > requests > > > > >> > > > > > > > > > > > > > queued > > > > >> > > > > > > > > > > > > > > > in > > > > >> > > > > > > > > > > > > > > > > > the > > > > >> > > > > > > > > > > > > > > > > > > > broker will be no longer > > bounded > > > > by > > > > >> > > > > > > > > > > "queued.max.requests". > > > > >> > > > > > > > > > > > > This > > > > >> > > > > > > > > > > > > > > > > > probably > > > > >> > > > > > > > > > > > > > > > > > > > needs to be specified in the > > > > Public > > > > >> > > > > Interfaces > > > > >> > > > > > > > > section > > > > >> > > > > > > > > > > for > > > > >> > > > > > > > > > > > > > > > > discussion. > > > > >> > > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > Thanks, > > > > >> > > > > > > > > > > > > > > > > > > > Dong > > > > >> > > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > On Wed, Jun 13, 2018 at > 12:45 > > > PM, > > > > >> Lucas > > > > >> > > > Wang > > > > >> > > > > < > > > > >> > > > > > > > > > > > > > > > lucasatu...@gmail.com > > > > > >> > > > > > > > > > > > > > > > > > > > wrote: > > > > >> > > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > Hi Kafka experts, > > > > >> > > > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > I created KIP-291 to add a > > > > >> separate > > > > >> > > queue > > > > >> > > > > for > > > > >> > > > > > > > > > > controller > > > > >> > > > > > > > > > > > > > > > requests: > > > > >> > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/ > > > > >> > > > > > > > > > confluence/display/KAFKA/KIP- > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > 291% > > > > >> > > > > > > > > > > > > > > > > > > > > > 3A+Have+separate+queues+for+ > > > > >> > > > > > > > > > control+requests+and+data+ > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > requests > > > > >> > > > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > Can you please take a look > > and > > > > >> let me > > > > >> > > > know > > > > >> > > > > > your > > > > >> > > > > > > > > > > feedback? > > > > >> > > > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > Thanks a lot for your > time! > > > > >> > > > > > > > > > > > > > > > > > > > > Regards, > > > > >> > > > > > > > > > > > > > > > > > > > > Lucas > > > > >> > > > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > > > > >> > > > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > >> > > > > > > > > > > > > > > > > > > > > > > -- > -Regards, > Mayuresh R. Gharat > (862) 250-7125 >
