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https://issues.apache.org/jira/browse/BEAM-1612?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15894345#comment-15894345
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Aljoscha Krettek commented on BEAM-1612:
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Yes, I think finding a solution for bundling is very important.
Right now, I'm afraid we have to manually induce bundling using either count or
time (or both). Making bundling dependent on snapshotting doesn't work because
Flink operators cannot (right now) emit data while snapshotting while a Beam
{{DoFn}} can emit data in the {{@FinishBundle}} method.
> Support real Bundle in Flink runner
> -----------------------------------
>
> Key: BEAM-1612
> URL: https://issues.apache.org/jira/browse/BEAM-1612
> Project: Beam
> Issue Type: Improvement
> Components: runner-flink
> Reporter: Jingsong Lee
> Assignee: Jingsong Lee
>
> The Bundle is very important in the beam model. Users can use the bundle to
> flush buffer, can reuse many heavyweight resources in a bundle. Most IO
> plugins use the bundle to flush.
> Moreover, FlinkRunner can also use Bundle to reduce access to the FlinkState,
> such as first placed in JavaHeap, flush into RocksDbState when invoke
> finishBundle , this can reduce the number of serialization.
> But now FlinkRunner calls the finishBundle every processElement. We need
> support real Bundle.
> I think we can have the following implementations:
> 1.Invoke finishBundle and next startBundle in {{snapshot}} of Flink. But
> sometimes this "Bundle" maybe too big. This depends on the user's checkpoint
> configuration.
> 2.Manually control the size of the bundle. The half-bundle will be flushed to
> a full-bundle by count or eventTime or processTime or {{snapshot}}. We do not
> need to wait, just call the startBundle and finishBundle at the right time.
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