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https://issues.apache.org/jira/browse/BEAM-3499?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Eugene Kirpichov closed BEAM-3499.
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Resolution: Fixed
Fix Version/s: 2.3.0
> Watch can make no progress if a single poll takes more than checkpoint
> interval
> -------------------------------------------------------------------------------
>
> Key: BEAM-3499
> URL: https://issues.apache.org/jira/browse/BEAM-3499
> Project: Beam
> Issue Type: Bug
> Components: sdk-java-core
> Reporter: Eugene Kirpichov
> Assignee: Eugene Kirpichov
> Priority: Major
> Fix For: 2.3.0
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> E.g. when using it to poll a filepattern with hundreds of thousands of files,
> a single poll may take >10 seconds (default checkpoint interval in
> OutputAndTimeBoundedSplittableProcessElementInvoker). Because of that, the
> tracker (GrowthTracker) gets checkpointed before anything is added to it,
> i.e. before
> [https://github.com/apache/beam/blob/0d918b7cab8c4ccb2b5e050501327912161d40a7/sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/Watch.java#L727,]
> at a moment when it doesn't contain any useful information, so the residual
> checkpoint state is as empty as the initial one. When we resume from the
> residual checkpoint, the situation simply repeats - until we get lucky enough
> to either take <10s to poll, or to not be asked to checkpoint for >10s (e.g.
> cause the checkpointing thread isn't scheduled).
> One possible fix to this is to change the SDF checkpointing strategy to have
> a progress guarantee: e.g., start counting time from the moment the first
> block is claimed, or allow the tracker to refuse checkpointing if nothing is
> claimed yet, or something like that.
>
> A workaround for users of this (primarily via FileIO.match().continuously())
> is to shard their filepattern into a set of finer-granularity filepatterns
> matching fewer files, so that each match call takes less than 10 seconds.
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