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https://issues.apache.org/jira/browse/BEAM-2680?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17179860#comment-17179860
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Beam JIRA Bot commented on BEAM-2680:
-------------------------------------
This issue is P2 but has been unassigned without any comment for 60 days so it
has been labeled "stale-P2". If this issue is still affecting you, we care!
Please comment and remove the label. Otherwise, in 14 days the issue will be
moved to P3.
Please see https://beam.apache.org/contribute/jira-priorities/ for a detailed
explanation of what these priorities mean.
> Improve scalability of the Watch transform
> ------------------------------------------
>
> Key: BEAM-2680
> URL: https://issues.apache.org/jira/browse/BEAM-2680
> Project: Beam
> Issue Type: Bug
> Components: sdk-java-core
> Reporter: Eugene Kirpichov
> Priority: P2
> Labels: stale-P2
>
> [https://github.com/apache/beam/pull/3565] introduces the Watch transform
> [http://s.apache.org/beam-watch-transform].
> The implementation leaves several scalability-related TODOs:
> 1) The state stores hashes and timestamps of outputs that have already been
> output and should be omitted from future polls. We could garbage-collect this
> state, e.g. dropping elements from "completed" and from addNewAsPending() if
> their timestamp is more than X behind the watermark.
> 2) When a poll returns a huge number of elements, we don't necessarily have
> to add all of them into state.pending - instead we could add only N oldest
> elements and ignore others, relying on future poll rounds to provide them, in
> order to avoid blowing up the state. Combined with garbage collection of
> GrowthState.completed, this would make the transform scalable to very large
> poll results.
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