Hello Hao, Thanks for the proposal, I have some preference among the options here so I will copy them here:
I'm now thinking if it's better to not add this new config on each of the Window interfaces, but instead add that at the KGroupedStream#windowedBy function. Also instead of adding just a boolean flag, maybe we can add a Configured class like Grouped, Suppressed, etc, e.g. let's call it a Emitted which for now would just have a single construct as Emitted.atWindowClose whose semantics is the same as emitFinal == true. I think the benefits are: 1) you do not need to modify multiple Window classes, but just overload one windowedBy function with a second param. This is less of a scope for now, and also more extensible for any future changes. 2) With a config interface, we maintain its extensibility as well as being able to reuse this Emitted interface for other operators if we wanted to expand to. ---------------------------- So in general I'm leaning towards option 2). For that, some more detailed comments: 1) If we want to reuse that config object for other non-window stateful operations, I think naming it as `EmitConfig` is probably better than `WindowConfig`. 2) I saw your PR (https://github.com/apache/kafka/pull/11892) that you are also proposing to add new stores into the public factory Stores, but it's not included in the KIP. Is that intentional? Personally I think that although we may eventually want to add a new store type to the public APIs, for this KIP maybe we do not have to add them but can delay for later after we've learned the best way to layout. LMK what do you think? Guozhang On Fri, Mar 11, 2022 at 2:13 PM Hao Li <h...@confluent.io.invalid> wrote: > Hi Dev team, > > I'd like to start a discussion thread on Kafka Streams KIP-825: > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-825%3A+introduce+a+new+API+to+control+when+aggregated+results+are+produced > > This KIP is aimed to add new APIs to support outputting final aggregated > results for windowed aggregations. I listed several options there and I'm > looking forward to your feedback. > > Thanks, > Hao > -- -- Guozhang
