Hi folks, Since there are actually a long interleaved discussions in KAFKA-1660 and KAFKA-1659, I summarized them in the rejected alternatives sections - the section exists for a reason and I shouldn’t have always put None there. . . It looks we took a while to agree upon the current interface.
We basically has the following requirements: *Assuming request timeout is available* 1. Need to close a producer forcefully if a message send failed. 2. Need to close a producer forcefully even if no message send failed. 3. Need to close a producer elegantly but with a bounded waiting time. 4. Need to close a producer forcefully after an arbitrary waiting time other than request timeout. The options we have now are (): A. close(timeout) - address all four. B. Close() + abort.on.send.fail - address 1) and 3) C. abort() + close() - address 1) and 2) and 3) So I think we can narrow the discussion to be whether 2) and 4) are valid use case or not. As soon as we reach conclusion on what requirements need to be met, we would have a conclusion to the solution. I think 2) might be a valid because of some application level logic. I am not sure if 4) is a valid requirement, but form KAFKA-1660, my understanding is it is. Any idea? Jiangjie (Becket) Qin On 3/12/15, 11:50 AM, "Jiangjie Qin" <j...@linkedin.com> wrote: >Hey Guozhang, > >Thanks for the comments. I updated the page as suggested. >For 3), that’s right, I put this in java doc. Do you think we need to >reject value other than -1? >For 4), I think user will notice this easily because the thread will block >and producer is not going to shutdown. About using close(-1) quietly in >sender thread when close() is called, my concern is that user might not be >aware of that. Maybe we can put an error messages if user call close() in >sender thread? > >Thanks, > >Jiangjie (Becket) Qin > >On 3/12/15, 5:13 AM, "Guozhang Wang" <wangg...@gmail.com> wrote: > >>Hi Becket, >> >>Some comments on the wiki page: >> >>1. There are a few typos, for example "multivations", "wiithin". >> >>2. I think the main motivation could just be "current close() needs to >>block on flushing all buffered data, however there are scenarios in which >>producers would like to close without blocking on flushing data, or even >>close immediately and make sure any buffered data are dropped instead of >>sending out." You can probably give some examples for such scenarios. >> >>3. close(-1, TimeUnit.MILLISECONDS) => from the implementation it seems >>any >>negative value has the same semantics. >> >>4. In sender thread only close(-1, TimeUnit.MILLISECONDS) should be >>called >>=> this is not programmatically enforced. Shall we just try to enforce it >>via, for example, checking if caller thread is the IO thread, and if yes >>just use close(-1)? >> >>5. Proposed Changes => it seems you only talked about the close(-1) case, >>how about close(>=0)? >> >>Guozhang >> >>On Thu, Mar 12, 2015 at 1:49 AM, Jiangjie Qin <j...@linkedin.com.invalid> >>wrote: >> >>> Hey Joe & Jay, >>> >>> Thanks for the comments on the voting thread. Since it seems we >>>probably >>> will have more discussion on this, I am just replying from the >>>discussion >>> thread here. >>> I’ve updated the KIP page to make it less like half-baked, apologize >>>for >>> the rush... >>> >>> The contract in current KIP is: >>> 1. close() - wait until all requests either are sent or reach request >>> timeout. >>> 2. close(-1, TimeUnit.MILLISECONDS) - close immediately >>> 3. close(0, TimeUnit.MILLISECONDS) - equivalent to close(), i.e. Wait >>> until all requests are sent or reach request timeout >>> 4. close(5, TimeUnit.MILLISECONDS) - try the best to finish sending >>>in 5 >>> milliseconds, if something went wrong, just shutdown the producer >>>anyway, >>> my callback will handle the failures. >>> >>> About how we define what timeout value stands for, I actually struggled >>>a >>> little bit when wrote the patch. Intuitively, close(0) should mean >>> immediately, however it seems that all the existing java class have >>>this >>> convention of timeout=0 means no timeout or never timeout >>>(Thread.join(0), >>> Object.wait(0), etc.) So here the dilemma is either we follow the >>> intuition or we follow the convention. What I chose is to follow the >>> convention but document the interface to let user be aware of the >>>usage. >>> The reason is that I think producer.close() is a public interface so it >>> might be better to follow java convention. Whereas selector is not a >>> public interface that used by user, so as long as it makes sense to us, >>>it >>> is less a problem to be different from java convention. That said since >>> consumer.poll(timeout) is also a public interface, I think it also >>>makes >>> sense to make producer.close() to have the same definition of >>> consumer.poll(timeout). >>> >>> The main argument for keeping a timeout in close would be separating >>>the >>> close timeout from request timeout, which probably makes sense. I would >>> guess typically the request timeout would be long (e.g. 60 seconds) >>> because we might want to consider retries with back off time. If we >>>have >>> multiple batches in accumulator, in worst case that could take up to >>> several minutes to complete all the requests. But when we close a >>> producer, we might not want to wait for that long as it might cause >>>some >>> other problem like deployment tool timeout. >>> >>> There is also a subtle difference between close(timeout) and >>> flush(timeout). The only purpose for flush() is to write data to the >>> broker, so it makes perfect sense to wait until request timeout. I >>>think >>> that is why flush(timeout) looks strange. On the other hand, the top >>> priority for close() is to close the producer rather than flush() data, >>>so >>> close(timeout) gives guarantee on bounded waiting for its main job. >>> >>> Sorry for the confusion about forceClose flag. It is not a public >>> interface. I mentioned it in Proposed Changes section which I thought >>>was >>> supposed to provide implementation details. >>> >>> Thanks again for all the comments and suggestions! >>> >>> Jiangjie (Becket) Qin >>> >>> On 3/10/15, 8:57 PM, "Jiangjie Qin" <j...@linkedin.com> wrote: >>> >>> >The KIP page has been updated per Jay¹s comments. >>> >I¹d like to initiate the voting process if no further comments are >>> >received by tomorrow. >>> > >>> >Jiangjie (Becket) Qin >>> > >>> >On 3/8/15, 9:45 AM, "Jay Kreps" <jay.kr...@gmail.com> wrote: >>> > >>> >>Hey Jiangjie, >>> >> >>> >>Can you capture the full motivation and use cases for the feature? >>>This >>> >>mentions your interest in having a way of aborting from inside the >>> >>Callback. But it doesn't really explain that usage or why other >>>people >>> >>would want to do that. It also doesn't list the primary use case for >>> >>having >>> >>close with a bounded timeout which was to avoid blocking too long on >>> >>shutdown. >>> >> >>> >>-Jay >>> >> >>> >> >>> >> >>> >>On Sat, Mar 7, 2015 at 12:25 PM, Jiangjie Qin >>><j...@linkedin.com.invalid >>> > >>> >>wrote: >>> >> >>> >>> Hi, >>> >>> >>> >>> I just created a KIP for adding a close(timeout) to new producer. >>>Most >>> >>>of >>> >>> the previous discussions are in KAFKA-1660 where Parth Brahmbhatt >>>has >>> >>> already done a lot of work. >>> >>> Since this is an interface change so we are going through the KIP >>> >>>process. >>> >>> Here is the KIP link: >>> >>> >>> >>> >>> >>>https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=5373978 >>> >>>2 >>> >>> >>> >>> Thanks. >>> >>> >>> >>> Jiangjie (Becket) Qin >>> >>> >>> > >>> >>> >> >> >>-- >>-- Guozhang >
