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https://issues.apache.org/jira/browse/FLINK-17122?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Konstantin Knauf updated FLINK-17122:
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Issue Type: Improvement (was: Wish)
As part of https://issues.apache.org/jira/browse/FLINK-22029 the "Wish" issue
type will be dropped. I changed this one to "Improvement" instead.
> Support InputSelectable and BoundedMultiInput operators with checkpointing
> --------------------------------------------------------------------------
>
> Key: FLINK-17122
> URL: https://issues.apache.org/jira/browse/FLINK-17122
> Project: Flink
> Issue Type: Improvement
> Components: Runtime / Checkpointing, Runtime / Network
> Affects Versions: 1.9.2, 1.10.0
> Reporter: Piotr Nowojski
> Priority: Major
>
> Currently when user defined some {{InputSelectable}} or {{BoundedMultiInput}}
> operators, checkpointing is not supported. Main problem is the that
> combination of {{InputSelectable}} and barrier alignment can lead to
> deadlocks (checkpoint barrier stuck on not selected channel).
> Problem could be somehow mitigated via unaligned checkpoints (FLINK-14551),
> but not fully. Even with unaligned checkpoints, checkpoint barriers can be
> stuck in the job graph if there is a {{flatMap}} operator (or non {{flatMap}}
> operator but if records are spanning multiple buffers), blocked in the middle
> of processing by some down stream input selection. In such case we are not
> able to perform unaligned checkpoint.
> Potential solution could be using persistent communication channels or
> detecting before mentioned situations and avoid the dead lock by spilling
> excess data.
> As most of the problems are with input selections that are randomly flipping,
> there might be some partial solution for more trivial cases, like reading one
> side of an input fully before the other.
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