Hi Ewen, Yeah, I mentioned KAFKA-2391 where some of this was discussed. Jay was against having timeouts in the methods at the time. However, as Jason said offline, we did end up with a timeout parameter in `poll`.
Ismael On Fri, Mar 23, 2018 at 4:26 PM, Ewen Cheslack-Postava <e...@confluent.io> wrote: > Regarding the flexibility question, has someone tried to dig up the > discussion of the new consumer APIs when they were being written? I vaguely > recall these exact questions about using APIs vs configs and flexibility vs > bloating the API surface area having already been discussed. (Not that we > shouldn't revisit, just that it might also be a faster way to get to a full > understanding of the options, concerns, and tradeoffs). > > -Ewen > > On Thu, Mar 22, 2018 at 7:19 AM, Richard Yu <yohan.richard...@gmail.com> > wrote: > > > I do have one question though: in the current KIP, throwing > > TimeoutException to mark > > that time limit is exceeded is applied to all new methods introduced in > > this proposal. > > However, how would users respond when a TimeoutException (since it is > > considered > > a RuntimeException)? > > > > Thanks, > > Richard > > > > > > > > On Mon, Mar 19, 2018 at 6:10 PM, Richard Yu <yohan.richard...@gmail.com> > > wrote: > > > > > Hi Ismael, > > > > > > You have a great point. Since most of the methods in this KIP have > > similar > > > callbacks (position() and committed() both use fetchCommittedOffsets(), > > > and > > > commitSync() is similar to position(), except just updating offsets), > the > > > amount of time > > > they block should be also about equal. > > > > > > However, I think that we need to take into account a couple of things. > > For > > > starters, > > > if the new methods were all reliant on one config, there is likelihood > > > that the > > > shortcomings for this approach would be similar to what we faced if we > > let > > > request.timeout.ms control all method timeouts. In comparison, adding > > > overloads > > > does not have this problem. > > > > > > If you have further thoughts, please let me know. > > > > > > Richard > > > > > > > > > On Mon, Mar 19, 2018 at 5:12 PM, Ismael Juma <ism...@juma.me.uk> > wrote: > > > > > >> Hi, > > >> > > >> An option that is not currently covered in the KIP is to have a > separate > > >> config max.block.ms, which is similar to the producer config with the > > >> same > > >> name. This came up during the KAFKA-2391 discussion. I think it's > clear > > >> that we can't rely on request.timeout.ms, so the decision is between > > >> adding > > >> overloads or adding a new config. People seemed to be leaning towards > > the > > >> latter in KAFKA-2391, but Jason makes a good point that the overloads > > are > > >> more flexible. A couple of questions from me: > > >> > > >> 1. Do we need the additional flexibility? > > >> 2. If we do, do we need it for every blocking method? > > >> > > >> Ismael > > >> > > >> On Mon, Mar 19, 2018 at 5:03 PM, Richard Yu < > yohan.richard...@gmail.com > > > > > >> wrote: > > >> > > >> > Hi Guozhang, > > >> > > > >> > I made some clarifications to KIP-266, namely: > > >> > 1. Stated more specifically that commitSync will accept user input. > > >> > 2. fetchCommittedOffsets(): Made its role in blocking more clear to > > the > > >> > reader. > > >> > 3. Sketched what would happen when time limit is exceeded. > > >> > > > >> > These changes should make the KIP easier to understand. > > >> > > > >> > Cheers, > > >> > Richard > > >> > > > >> > On Mon, Mar 19, 2018 at 9:33 AM, Guozhang Wang <wangg...@gmail.com> > > >> wrote: > > >> > > > >> > > Hi Richard, > > >> > > > > >> > > I made a pass over the KIP again, some more clarifications / > > comments: > > >> > > > > >> > > 1. seek() call itself is not blocking, only the following poll() > > call > > >> may > > >> > > be blocking as the actually metadata rq will happen. > > >> > > > > >> > > 2. I saw you did not include Consumer.partitionFor(), > > >> > > Consumer.OffsetAndTimestamp() and Consumer.listTopics() in your > KIP. > > >> > After > > >> > > a second thought, I think this may be a better idea to not tackle > > >> them in > > >> > > the same KIP, and probably we should consider whether we would > > change > > >> the > > >> > > behavior or not in another discussion. So I agree to not include > > them. > > >> > > > > >> > > 3. In your wiki you mentioned "Another change shall be made to > > >> > > KafkaConsumer#poll(), due to its call to updateFetchPositions() > > which > > >> > > blocks indefinitely." This part may a bit obscure to most readers > > >> who's > > >> > not > > >> > > familiar with the KafkaConsumer internals, could you please add > more > > >> > > elaborations. More specifically, I think the root causes of the > > public > > >> > APIs > > >> > > mentioned are a bit different while the KIP's explanation sounds > > like > > >> > they > > >> > > are due to the same reason: > > >> > > > > >> > > 3.1 fetchCommittedOffsets(): this internal call will block forever > > if > > >> the > > >> > > committed offsets cannot be fetched successfully and affect > > position() > > >> > and > > >> > > committed(). We need to break out of its internal while loop. > > >> > > 3.2 position() itself will while loop when offsets cannot be > > >> retrieved in > > >> > > the underlying async call. We need to break out this while loop. > > >> > > 3.3 commitSync() passed Long.MAX_VALUE as the timeout value, we > > should > > >> > take > > >> > > the user specified timeouts when applicable. > > >> > > > > >> > > > > >> > > > > >> > > Guozhang > > >> > > > > >> > > On Sat, Mar 17, 2018 at 4:44 PM, Richard Yu < > > >> yohan.richard...@gmail.com> > > >> > > wrote: > > >> > > > > >> > > > Actually, what I said above is inaccurate. In > > >> > > > testSeekAndCommitWithBrokerFailures, TestUtils.waitUntilTrue > > >> blocks, > > >> > not > > >> > > > seek. > > >> > > > My assumption is that seek did not update correctly. I will be > > >> digging > > >> > > > further into this. > > >> > > > > > >> > > > > > >> > > > > > >> > > > On Sat, Mar 17, 2018 at 4:16 PM, Richard Yu < > > >> > yohan.richard...@gmail.com> > > >> > > > wrote: > > >> > > > > > >> > > > > One more thing: when looking through tests, I have realized > that > > >> > seek() > > >> > > > > methods can potentially block indefinitely. As you well know, > > >> seek() > > >> > is > > >> > > > > called when pollOnce() or position() is active. Thus, if > > >> position() > > >> > > > blocks > > >> > > > > indefinitely, then so would seek(). Should bounding seek() > also > > be > > >> > > > included > > >> > > > > in this KIP? > > >> > > > > > > >> > > > > Thanks, Richard > > >> > > > > > > >> > > > > On Sat, Mar 17, 2018 at 1:16 PM, Richard Yu < > > >> > > yohan.richard...@gmail.com> > > >> > > > > wrote: > > >> > > > > > > >> > > > >> Thanks for the advice, Jason > > >> > > > >> > > >> > > > >> I have modified KIP-266 to include the java doc for > committed() > > >> and > > >> > > > other > > >> > > > >> blocking methods, and I also > > >> > > > >> mentioned poll() which will also be bounded. Let me know if > > >> there is > > >> > > > >> anything else. :) > > >> > > > >> > > >> > > > >> Sincerely, Richard > > >> > > > >> > > >> > > > >> > > >> > > > >> > > >> > > > >> > > >> > > > >> > > >> > > > >> On Sat, Mar 17, 2018 at 12:00 PM, Jason Gustafson < > > >> > ja...@confluent.io > > >> > > > > > >> > > > >> wrote: > > >> > > > >> > > >> > > > >>> Hi Richard, > > >> > > > >>> > > >> > > > >>> Thanks for the updates. I'm really glad you picked this up. > A > > >> > couple > > >> > > > >>> minor > > >> > > > >>> comments: > > >> > > > >>> > > >> > > > >>> 1. Can you list the full set of new APIs explicitly in the > > KIP? > > >> > > > >>> Currently I > > >> > > > >>> only see the javadoc for `position()`. > > >> > > > >>> > > >> > > > >>> 2. We should consider adding `TimeUnit` to the new methods > to > > >> avoid > > >> > > > unit > > >> > > > >>> confusion. I know it's inconsistent with the poll() API, > but I > > >> > think > > >> > > it > > >> > > > >>> was > > >> > > > >>> probably a mistake not to include it there, so better not to > > >> double > > >> > > > down > > >> > > > >>> on > > >> > > > >>> that mistake. And note that we do already have `close(long, > > >> > > TimeUnit)`. > > >> > > > >>> > > >> > > > >>> Other than that, I think the current KIP seems reasonable. > > >> > > > >>> > > >> > > > >>> Thanks, > > >> > > > >>> Jason > > >> > > > >>> > > >> > > > >>> On Wed, Mar 14, 2018 at 5:00 PM, Richard Yu < > > >> > > > yohan.richard...@gmail.com> > > >> > > > >>> wrote: > > >> > > > >>> > > >> > > > >>> > Note to all: I have included bounding commitSync() and > > >> > committed() > > >> > > in > > >> > > > >>> this > > >> > > > >>> > KIP. > > >> > > > >>> > > > >> > > > >>> > On Sun, Mar 11, 2018 at 5:05 PM, Richard Yu < > > >> > > > >>> yohan.richard...@gmail.com> > > >> > > > >>> > wrote: > > >> > > > >>> > > > >> > > > >>> > > Hi all, > > >> > > > >>> > > > > >> > > > >>> > > I updated the KIP where overloading position() is now > the > > >> > favored > > >> > > > >>> > approach. > > >> > > > >>> > > Bounding position() using requestTimeoutMs has been > listed > > >> as > > >> > > > >>> rejected. > > >> > > > >>> > > > > >> > > > >>> > > Any thoughts? > > >> > > > >>> > > > > >> > > > >>> > > On Tue, Mar 6, 2018 at 6:00 PM, Guozhang Wang < > > >> > > wangg...@gmail.com> > > >> > > > >>> > wrote: > > >> > > > >>> > > > > >> > > > >>> > >> I agree that adding the overloads is most flexible. But > > >> going > > >> > > for > > >> > > > >>> that > > >> > > > >>> > >> direction we'd do that for all the blocking call that > > I've > > >> > > listed > > >> > > > >>> above, > > >> > > > >>> > >> with this timeout value covering the end-to-end waiting > > >> time. > > >> > > > >>> > >> > > >> > > > >>> > >> > > >> > > > >>> > >> Guozhang > > >> > > > >>> > >> > > >> > > > >>> > >> On Tue, Mar 6, 2018 at 10:02 AM, Ted Yu < > > >> yuzhih...@gmail.com> > > >> > > > >>> wrote: > > >> > > > >>> > >> > > >> > > > >>> > >> > bq. The most flexible option is to add overloads to > the > > >> > > consumer > > >> > > > >>> > >> > > > >> > > > >>> > >> > This option is flexible. > > >> > > > >>> > >> > > > >> > > > >>> > >> > Looking at the tail of SPARK-18057, Spark dev voiced > > the > > >> > same > > >> > > > >>> choice. > > >> > > > >>> > >> > > > >> > > > >>> > >> > +1 for adding overload with timeout parameter. > > >> > > > >>> > >> > > > >> > > > >>> > >> > Cheers > > >> > > > >>> > >> > > > >> > > > >>> > >> > On Mon, Mar 5, 2018 at 2:42 PM, Jason Gustafson < > > >> > > > >>> ja...@confluent.io> > > >> > > > >>> > >> > wrote: > > >> > > > >>> > >> > > > >> > > > >>> > >> > > @Guozhang I probably have suggested all options at > > some > > >> > > point > > >> > > > or > > >> > > > >>> > >> another, > > >> > > > >>> > >> > > including most recently, the current KIP! I was > > >> thinking > > >> > > that > > >> > > > >>> > >> practically > > >> > > > >>> > >> > > speaking, the request timeout defines how long the > > >> user is > > >> > > > >>> willing > > >> > > > >>> > to > > >> > > > >>> > >> > wait > > >> > > > >>> > >> > > for a response. The consumer doesn't really have a > > >> complex > > >> > > > send > > >> > > > >>> > >> process > > >> > > > >>> > >> > > like the producer for any of these APIs, so I > wasn't > > >> sure > > >> > > how > > >> > > > >>> much > > >> > > > >>> > >> > benefit > > >> > > > >>> > >> > > there would be from having more granular control > over > > >> > > timeouts > > >> > > > >>> (in > > >> > > > >>> > the > > >> > > > >>> > >> > end, > > >> > > > >>> > >> > > KIP-91 just adds a single timeout to control the > > whole > > >> > > send). > > >> > > > >>> That > > >> > > > >>> > >> said, > > >> > > > >>> > >> > it > > >> > > > >>> > >> > > might indeed be better to avoid overloading the > > config > > >> as > > >> > > you > > >> > > > >>> > suggest > > >> > > > >>> > >> > since > > >> > > > >>> > >> > > at least it avoids inconsistency with the > producer's > > >> > usage. > > >> > > > >>> > >> > > > > >> > > > >>> > >> > > The most flexible option is to add overloads to the > > >> > consumer > > >> > > > so > > >> > > > >>> that > > >> > > > >>> > >> > users > > >> > > > >>> > >> > > can pass the timeout directly. I'm not sure if that > > is > > >> > more > > >> > > or > > >> > > > >>> less > > >> > > > >>> > >> > > annoying than a new config, but I've found config > > >> > timeouts a > > >> > > > >>> little > > >> > > > >>> > >> > > constraining in practice. For example, I could > > imagine > > >> > users > > >> > > > >>> wanting > > >> > > > >>> > >> to > > >> > > > >>> > >> > > wait longer for an offset commit operation than a > > >> position > > >> > > > >>> lookup; > > >> > > > >>> > if > > >> > > > >>> > >> the > > >> > > > >>> > >> > > latter isn't timely, users can just pause the > > partition > > >> > and > > >> > > > >>> continue > > >> > > > >>> > >> > > fetching on others. If you cannot commit offsets, > > >> however, > > >> > > it > > >> > > > >>> might > > >> > > > >>> > be > > >> > > > >>> > >> > > safer for an application to wait availability of > the > > >> > > > coordinator > > >> > > > >>> > than > > >> > > > >>> > >> > > continuing. > > >> > > > >>> > >> > > > > >> > > > >>> > >> > > -Jason > > >> > > > >>> > >> > > > > >> > > > >>> > >> > > On Sun, Mar 4, 2018 at 10:14 PM, Guozhang Wang < > > >> > > > >>> wangg...@gmail.com> > > >> > > > >>> > >> > wrote: > > >> > > > >>> > >> > > > > >> > > > >>> > >> > > > Hello Richard, > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > Thanks for the proposed KIP. I have a couple of > > >> general > > >> > > > >>> comments: > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > 1. I'm not sure if piggy-backing the timeout > > >> exception > > >> > on > > >> > > > the > > >> > > > >>> > >> > > > existing requestTimeoutMs configured in " > > >> > > request.timeout.ms > > >> > > > " > > >> > > > >>> is a > > >> > > > >>> > >> good > > >> > > > >>> > >> > > > idea > > >> > > > >>> > >> > > > since a) it is a general config that applies for > > all > > >> > types > > >> > > > of > > >> > > > >>> > >> requests, > > >> > > > >>> > >> > > and > > >> > > > >>> > >> > > > 2) using it to cover all the phases of an API > call, > > >> > > > including > > >> > > > >>> > >> network > > >> > > > >>> > >> > > round > > >> > > > >>> > >> > > > trip and potential metadata refresh is shown to > not > > >> be a > > >> > > > good > > >> > > > >>> > idea, > > >> > > > >>> > >> as > > >> > > > >>> > >> > > > illustrated in KIP-91: > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > https://cwiki.apache.org/confl > > >> uence/display/KAFKA/KIP- > > >> > > > >>> > >> > > > 91+Provide+Intuitive+User+ > Timeouts+in+The+Producer > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > In fact, I think in KAFKA-4879 which is aimed for > > the > > >> > same > > >> > > > >>> issue > > >> > > > >>> > as > > >> > > > >>> > >> > > > KAFKA-6608, > > >> > > > >>> > >> > > > Jason has suggested we use a new config for the > > API. > > >> > Maybe > > >> > > > >>> this > > >> > > > >>> > >> would > > >> > > > >>> > >> > be > > >> > > > >>> > >> > > a > > >> > > > >>> > >> > > > more intuitive manner than reusing the > > >> > request.timeout.ms > > >> > > > >>> config. > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > 2. Besides the Consumer.position() call, there > are > > a > > >> > > couple > > >> > > > of > > >> > > > >>> > more > > >> > > > >>> > >> > > > blocking calls today that could result in > infinite > > >> > > blocking: > > >> > > > >>> > >> > > > Consumer.commitSync() and Consumer.committed(), > > >> should > > >> > > they > > >> > > > be > > >> > > > >>> > >> > considered > > >> > > > >>> > >> > > > in this KIP as well? > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > 3. There are a few other APIs that are today > > relying > > >> on > > >> > > > >>> > >> > > request.timeout.ms > > >> > > > >>> > >> > > > already for breaking the infinite blocking, > namely > > >> > > > >>> > >> > > Consumer.partitionFor(), > > >> > > > >>> > >> > > > Consumer.OffsetAndTimestamp() and > > >> Consumer.listTopics(), > > >> > > if > > >> > > > >>> we are > > >> > > > >>> > >> > making > > >> > > > >>> > >> > > > the other blocking calls to be relying a new > config > > >> as > > >> > > > >>> suggested > > >> > > > >>> > in > > >> > > > >>> > >> 1) > > >> > > > >>> > >> > > > above, should we also change the semantics of > these > > >> API > > >> > > > >>> functions > > >> > > > >>> > >> for > > >> > > > >>> > >> > > > consistency? > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > Guozhang > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > On Sun, Mar 4, 2018 at 11:13 AM, Richard Yu < > > >> > > > >>> > >> > yohan.richard...@gmail.com> > > >> > > > >>> > >> > > > wrote: > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > > Hi all, > > >> > > > >>> > >> > > > > > > >> > > > >>> > >> > > > > I would like to discuss a potential change > which > > >> would > > >> > > be > > >> > > > >>> made > > >> > > > >>> > to > > >> > > > >>> > >> > > > > KafkaConsumer: > > >> > > > >>> > >> > > > > https://cwiki.apache.org/ > > confluence/pages/viewpage > > >> . > > >> > > > >>> > >> > > > action?pageId=75974886 > > >> > > > >>> > >> > > > > > > >> > > > >>> > >> > > > > Thanks, > > >> > > > >>> > >> > > > > Richard Yu > > >> > > > >>> > >> > > > > > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > -- > > >> > > > >>> > >> > > > -- Guozhang > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > > >> > > > >>> > >> > > > >> > > > >>> > >> > > >> > > > >>> > >> > > >> > > > >>> > >> > > >> > > > >>> > >> -- > > >> > > > >>> > >> -- Guozhang > > >> > > > >>> > >> > > >> > > > >>> > > > > >> > > > >>> > > > > >> > > > >>> > > > >> > > > >>> > > >> > > > >> > > >> > > > >> > > >> > > > > > > >> > > > > > >> > > > > >> > > > > >> > > > > >> > > -- > > >> > > -- Guozhang > > >> > > > > >> > > > >> > > > > > > > > >
