Thanks Bruno for the great points. I see 2 options here =>
1) As Chris suggested, drop the support for dropping records in the partitioner. That way, an empty list could signify the usage of a default partitioner. Also, if the deprecated partition() method returns null thereby signifying the default partitioner, the partitions() can return an empty list i.e default partitioner. 2) OR we treat a null return type of partitions() method to signify the usage of the default partitioner. In the default implementation of partitions() method, if partition() returns null, then even partitions() can return null(instead of an empty list). The RecordCollectorImpl code can also be modified accordingly. @Chris, to your point, we can even drop the support of dropping of records. It came up during KIP discussion, and I thought it might be a useful feature. Let me know what you think. 3) Lastly about the partition number check. I wanted to avoid the throwing of exception so I thought adding it might be a useful feature. But as you pointed out, if it can break backwards compatibility, it's better to remove it. Thanks! Sagar. On Tue, Aug 30, 2022 at 6:32 PM Chris Egerton <chr...@aiven.io.invalid> wrote: > +1 to Bruno's concerns about backward compatibility. Do we actually need > support for dropping records in the partitioner? It doesn't seem necessary > based on the motivation for the KIP. If we remove that feature, we could > handle null and/or empty lists by using the default partitioning, > equivalent to how we handle null return values from the existing partition > method today. > > On Tue, Aug 30, 2022 at 8:55 AM Bruno Cadonna <cado...@apache.org> wrote: > > > Hi Sagar, > > > > Thank you for the updates! > > > > I do not intend to prolong this vote thread more than needed, but I > > still have some points. > > > > The deprecated partition method can return null if the default > > partitioning logic of the producer should be used. > > With the new method partitions() it seems that it is not possible to use > > the default partitioning logic, anymore. > > > > Also, in the default implementation of method partitions(), a record > > that would use the default partitioning logic in method partition() > > would be dropped, which would break backward compatibility since Streams > > would always call the new method partitions() even though the users > > still implement the deprecated method partition(). > > > > I have a last point that we should probably discuss on the PR and not on > > the KIP but since you added the code in the KIP I need to mention it. I > > do not think you should check the validity of the partition number since > > the ProducerRecord does the same check and throws an exception. If > > Streams adds the same check but does not throw, the behavior is not > > backward compatible. > > > > Best, > > Bruno > > > > > > On 30.08.22 12:43, Sagar wrote: > > > Thanks Bruno/Chris, > > > > > > Even I agree that might be better to keep it simple like the way Chris > > > suggested. I have updated the KIP accordingly. I made couple of minor > > > changes to the KIP: > > > > > > 1) One of them being the change of return type of partitions method > from > > > List to Set. This is to ensure that in case the implementation of > > > StreamPartitoner is buggy and ends up returning duplicate > > > partition numbers, we won't have duplicates thereby not trying to send > to > > > the same partition multiple times due to this. > > > 2) I also added a check to send the record only to valid partition > > numbers > > > and log and drop when the partition number is invalid. This is again to > > > prevent errors for cases when the StreamPartitioner implementation has > > some > > > bugs (since there are no validations as such). > > > 3) I also updated the Test Plan section based on the suggestion from > > Bruno. > > > 4) I updated the default implementation of partitions method based on > the > > > great catch from Chris! > > > > > > Let me know if it looks fine now. > > > > > > Thanks! > > > Sagar. > > > > > > > > > On Tue, Aug 30, 2022 at 3:00 PM Bruno Cadonna <cado...@apache.org> > > wrote: > > > > > >> Hi, > > >> > > >> I am favour of discarding the sugar for broadcasting and leave the > > >> broadcasting to the implementation as Chris suggests. I think that is > > >> the cleanest option. > > >> > > >> Best, > > >> Bruno > > >> > > >> On 29.08.22 19:50, Chris Egerton wrote: > > >>> Hi all, > > >>> > > >>> I think it'd be useful to be more explicit about broadcasting to all > > >> topic > > >>> partitions rather than add implicit behavior for empty cases (empty > > >>> optional, empty list, etc.). The suggested enum approach would > address > > >> that > > >>> nicely. > > >>> > > >>> It's also worth noting that there's no hard requirement to add sugar > > for > > >>> broadcasting to all topic partitions since the API already provides > the > > >>> number of topic partitions available when calling a stream > partitioner. > > >> If > > >>> we can't find a clean way to add this support, it might be better to > > >> leave > > >>> it out and just let people implement this themselves with a line of > > Java > > >> 8 > > >>> streams: > > >>> > > >>> return IntStream.range(0, > > >>> numPartitions).boxed().collect(Collectors.toList()); > > >>> > > >>> Also worth noting that there may be a bug in the default > implementation > > >> for > > >>> the new StreamPartitioner::partitions method, since it doesn't appear > > to > > >>> correctly pick up on null return values from the partition method and > > >>> translate them into empty lists. > > >>> > > >>> Cheers, > > >>> > > >>> Chris > > >>> > > >>> On Mon, Aug 29, 2022 at 7:32 AM Bruno Cadonna <cado...@apache.org> > > >> wrote: > > >>> > > >>>> Hi Sagar, > > >>>> > > >>>> I do not see an issue with using an empty list together with an > empty > > >>>> Optional. A non-empty Optional that contains an empty list would > just > > >>>> say that there is no partition to which the record should be sent. > If > > >>>> there is no partition, the record is dropped. > > >>>> > > >>>> An empty Optional might be a way to say, broadcast to all > partitions. > > >>>> > > >>>> Alternatively -- to make it more explicit -- you could return an > > object > > >>>> with an enum and a list of partitions. The enum could have values > > SOME, > > >>>> ALL, and NONE. If the value is SOME, the list of partitions contains > > the > > >>>> partitions to which to send the record. If the value of the enum is > > ALL > > >>>> or NONE, the list of partitions is not used and might be even null > > >>>> (since in that case the list should not be used and it would be a > bug > > to > > >>>> use it). > > >>>> > > >>>> Best, > > >>>> Bruno > > >>>> > > >>>> On 24.08.22 20:11, Sagar wrote: > > >>>>> Thank you Bruno/Matthew for your comments. > > >>>>> > > >>>>> I agree using null does seem error prone. However I think using a > > >>>> singleton > > >>>>> list of [-1] might be better in terms of usability, I am saying > this > > >>>>> because the KIP also has a provision to return an empty list to > refer > > >> to > > >>>>> dropping the record. So, an empty optional and an empty list have > > >> totally > > >>>>> different meanings which could get confusing. > > >>>>> > > >>>>> Let me know what you think. > > >>>>> > > >>>>> Thanks! > > >>>>> Sagar. > > >>>>> > > >>>>> > > >>>>> On Wed, Aug 24, 2022 at 7:30 PM Matthew Benedict de Detrich > > >>>>> <matthew.dedetr...@aiven.io.invalid> wrote: > > >>>>> > > >>>>>> I also concur with this, having an Optional in the type makes it > > very > > >>>>>> clear what’s going on and better signifies an absence of value (or > > in > > >>>> this > > >>>>>> case the broadcast value). > > >>>>>> > > >>>>>> -- > > >>>>>> Matthew de Detrich > > >>>>>> Aiven Deutschland GmbH > > >>>>>> Immanuelkirchstraße 26, 10405 Berlin > > >>>>>> Amtsgericht Charlottenburg, HRB 209739 B > > >>>>>> > > >>>>>> Geschäftsführer: Oskari Saarenmaa & Hannu Valtonen > > >>>>>> m: +491603708037 > > >>>>>> w: aiven.io e: matthew.dedetr...@aiven.io > > >>>>>> On 24. Aug 2022, 14:19 +0200, dev@kafka.apache.org, wrote: > > >>>>>>> > > >>>>>>> 2. > > >>>>>>> I would prefer changing the return type of partitions() to > > >>>>>>> Optional<List<Integer>> and using Optional.empty() as the > broadcast > > >>>>>>> value. IMO, The chances that an implementation returns null due > to > > a > > >>>> bug > > >>>>>>> is much higher than that an implementation returns an empty > > Optional > > >>>> due > > >>>>>>> to a bug. > > >>>>>> > > >>>>> > > >>>> > > >>> > > >> > > > > > >
