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https://issues.apache.org/jira/browse/BEAM-12654?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17418236#comment-17418236
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Beam JIRA Bot commented on BEAM-12654:
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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.
> FileIO can produce duplicates in output files
> ---------------------------------------------
>
> Key: BEAM-12654
> URL: https://issues.apache.org/jira/browse/BEAM-12654
> Project: Beam
> Issue Type: Bug
> Components: sdk-java-core
> Reporter: Jozef Vilcek
> Priority: P2
> Labels: stale-P2
>
> FileIO can produce duplicates in output files - depending on a runner.
> Concrete example for Spark when executing as batch:
> When using FileIO with specific number of shards, it will use default
> sharding function which is a round robin shard assignment with random seed.
> In multistage pipeline, data between stages are hold by shuffle service until
> downstream stage request it for further computations. If shuffle results
> computed with this seeded shard function are lost - e.g. shuffle service
> fails because of HW error - then Spark will attempt to recover data by
> computing them again from source data. As a result of a random seed sharding,
> this will assign different shard - and therefore key to the element.
> More details are discussed in this thread:
> https://lists.apache.org/thread.html/r5e91d1996479defbf5e896dca3cf237ee2d9b59396cb3c4edf619df1%40%3Cdev.beam.apache.org%3E
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