I didn't see user API or SDK changes that I would expect in this proposal. Maybe I missed it? The main big win for state batching in the runners core trigger & window implementation is batching requests across a whole bundle. Certainly across elements. This probably requires something like either:
- a user API change (to have something like this: https://github.com/apache/beam/blob/f47a9424723e20abf807098dd6e9eef6e74c16cc/runners/core-java/src/main/java/org/apache/beam/runners/core/triggers/AfterAllStateMachine.java#L52 ) - the SDK to use metadata/annotations (like this: https://github.com/apache/beam/blob/f47a9424723e20abf807098dd6e9eef6e74c16cc/sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/DoFn.java#L420) instead That will allow the hints to be gathered across multiple elements. And it would see the Fn API streaming protocol might mean the implementation is different than it is in ReduceFnRunner. Kenn On Mon, Jun 14, 2021 at 2:46 PM Luke Cwik <lc...@google.com> wrote: > The third approach prevents you from batching across state keys which > would be the most common type of batching. > > On Thu, May 6, 2021 at 3:13 PM Rui Wang <ruw...@google.com> wrote: > >> At this moment, the third approach in the doc is preferred. To recap, the >> third approach is the one that only changes FnApi by adding a repeated >> field in the state request to support batching over FnApi. >> >> This approach has the following benefits: >> 1. Avoid double requests problem introduced by prefetching (prefetching >> needs two requests, one for prefetch and one for blocking fetch). >> 2. This approach does not conflict with prefetching so no backward >> compatibility issue even when we want to add prefetching in FnApi. So this >> approach can be a good starting point. >> >> The caveat though is this approach does not support smart prefetching >> (which needs runners support). However we can add that in the future if >> necessary and that won't conflict with existing design. >> >> Please let us know if you have any objection before the implementation. >> >> >> -Rui >> >> On Mon, Mar 22, 2021 at 12:27 PM Rui Wang <amaliu...@apache.org> wrote: >> >>> Hi Community, >>> >>> Andrew Crites and I drafted a document to discuss how to support state >>> prefetching and batching over FnApi, which seems a missing functionality in >>> FnApi. This will help us support Java state readLater() Api over FnApi. >>> >>> Please see: >>> https://docs.google.com/document/d/1Z3a5YOZyYsN8MeS6hRhCXX31m9bKCXSOtjKSl7wX40c/edit?usp=sharing&resourcekey=0-eiNl525kmb3Av2bqgCsZUA >>> >>> >>> -Rui >>> >>
