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https://issues.apache.org/jira/browse/BEAM-8848?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kenneth Knowles updated BEAM-8848:
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Labels: stale-assigned (was: )
> Flink: Memory efficient GBK implementation for batch runner
> -----------------------------------------------------------
>
> Key: BEAM-8848
> URL: https://issues.apache.org/jira/browse/BEAM-8848
> Project: Beam
> Issue Type: Improvement
> Components: runner-flink
> Reporter: David Morávek
> Assignee: David Morávek
> Priority: P2
> Labels: stale-assigned
>
> In current batch runner, all the values for a single key need to fit in
> memory, because the resulting GBK iterable is materialized using "List" data
> structure.
> Implications:
> - This blocks user from using custom sharding in most of the IOs, as the
> whole shard needs to fit in memory.
> - Frequent OOM failures in case of skewed data (pipeline should be running
> slow instead of failing). This is super hard to debug for inexperienced user.
> We can do way better for non-merging windows, the same way we do for Spark
> runner. Only drawback is, that this implementation does not support result
> re-iterations. We'll support turning this implementation on and off, if user
> needs to trade off reiterations for memory efficiency.
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