[jira] [Closed] (FLINK-12142) Add beforeSnapshot method to StreamOperator interface

["Aljoscha Krettek (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-12142?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Aljoscha Krettek closed FLINK-12142.
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    Resolution: Not A Problem

> Add beforeSnapshot method to StreamOperator interface
> -----------------------------------------------------
>
>                 Key: FLINK-12142
>                 URL: https://issues.apache.org/jira/browse/FLINK-12142
>             Project: Flink
>          Issue Type: New Feature
>          Components: Runtime / Checkpointing
>            Reporter: Gyula Fora
>            Priority: Trivial
>
> Right now, when a stream task receives a triggerCheckpoint call, it immediately forwards the checkpoint barrier and performs the checkpoint operation under the checkpoint lock.
> This mechanism doesn't allow the stream operations to implement any logic that should be performed before the snapshot is triggered in order to ensure state consistency.
> Some examples would be:
>  * Flushing any state (or other kind of) cache that is implemented in the operator layer
>  * Wait for pending operations (maybe with a different async execution model)
> The method could for instance look simply like this in the StreamOperator interface:
>  {{default void beforeSnapshot(long checkpointId, long timestamp) throws Exception {};}} 
> This method should then be called before the barrier is sent downstream still outside the checkpoint lock.



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