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https://issues.apache.org/jira/browse/FLINK-7883?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16214858#comment-16214858
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Antoine Philippot commented on FLINK-7883:
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Hi [~Zentol],
The {{StoppableFunction}} with {{stop()}} method is similar to {{cancel()}}
method as it close the task/function.
The desired behaviour with {{StoppableFetchingSourceFunction}} (the name can be
changed if it lead to confusion) and the method {{stopFetching}} is to only
stop fetching the source stream without stop or cancel the task/function.
The main reason is to allow kafka offset commit once the savepoint is complete
which is not possible if the function is stop/cancel before.
> Stop fetching source before a cancel with savepoint
> ---------------------------------------------------
>
> Key: FLINK-7883
> URL: https://issues.apache.org/jira/browse/FLINK-7883
> Project: Flink
> Issue Type: Improvement
> Components: DataStream API, Kafka Connector, State Backends,
> Checkpointing
> Affects Versions: 1.4.0, 1.3.2
> Reporter: Antoine Philippot
>
> For a cancel with savepoint command, the JobManager trigger the cancel call
> once the savepoint is finished, but during the savepoint execution, kafka
> source continue to poll new messages which will not be part of the savepoint
> and will be replayed on the next application start.
> A solution could be to stop fetching the source stream task before triggering
> the savepoint.
> I suggest to add an interface {{StoppableFetchingSourceFunction}} with a
> method {{stopFetching}} that existant SourceFunction implementations could
> implement.
> We can add a {{stopFetchingSource}} property in
> {{CheckpointOptions}} class to pass the desired behaviour from
> {{JobManager.handleMessage(CancelJobWithSavepoint)}} to
> {{SourceStreamTask.triggerCheckpoint}}
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