[jira] [Closed] (BEAM-4242) Wait.on() is O(n)

["Eugene Kirpichov (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/BEAM-4242?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Eugene Kirpichov closed BEAM-4242.
----------------------------------
       Resolution: Fixed
    Fix Version/s: 2.5.0

> Wait.on() is O(n)
> -----------------
>
>                 Key: BEAM-4242
>                 URL: https://issues.apache.org/jira/browse/BEAM-4242
>             Project: Beam
>          Issue Type: Bug
>          Components: sdk-java-core
>            Reporter: Eugene Kirpichov
>            Assignee: Eugene Kirpichov
>            Priority: Major
>             Fix For: 2.5.0
>
>          Time Spent: 1h 10m
>  Remaining Estimate: 0h
>
> Wait.on() uses a NeverTrigger and a Sample.any(1) as an implementation detail.
> Unfortunately, Sample.any() relies on combiner lifting for performance - otherwise all values end up grouped onto the same worker which is not acceptable if the signal PCollection is large.
> Not all runners support combiner lifting at all; and even those that do (e.g. Dataflow) don't guarantee it. In the case of a very large user's pipeline, combiner lifting was not performed because it's only supported for DefaultTrigger, but not for NeverTrigger.
> This should be fixed by modifying Wait to not rely on combiner lifting for performance, e.g. by a "manual" precombine (emit 1 value per bundle).
> CC: [~mkhadikov]



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