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https://issues.apache.org/jira/browse/FLINK-3089?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15897007#comment-15897007
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Aljoscha Krettek commented on FLINK-3089:
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Copying over my comment from FLINK-3946:
{quote}
I thought about this when adding the StateDescriptor interface a while back.
This would be the place to put a configuration value for the expiry. The state
backend would have to be given access to the internal timer service and it
would need to register timers for state that has expiry.
In order to make this pleasant we also need to abstract away the
processing-time and event-time timers behind interfaces. Right now, the window
operator has custom code to deal with watermark-based timers but if several
components start requiring this functionality we should put it behind a good
interface and let the AbstractStreamOperator handle it.
{quote}
> OperatorState timeout
> ---------------------
>
> Key: FLINK-3089
> URL: https://issues.apache.org/jira/browse/FLINK-3089
> Project: Flink
> Issue Type: New Feature
> Components: DataStream API, State Backends, Checkpointing
> Reporter: Niels Basjes
>
> In some usecases (webanalytics) there is a need to have a state per visitor
> on a website (i.e. keyBy(sessionid) ).
> At some point the visitor simply leaves and no longer creates new events (so
> a special 'end of session' event will not occur).
> The only way to determine that a visitor has left is by choosing a timeout,
> like "After 30 minutes no events we consider the visitor 'gone'".
> Only after this (chosen) timeout has expired should we discard this state.
> In the Trigger part of Windows we can set a timer and close/discard this kind
> of information. But that introduces the buffering effect of the window (which
> in some scenarios is unwanted).
> What I would like is to be able to set a timeout on a specific OperatorState
> value which I can update afterwards.
> This makes it possible to create a map function that assigns the right value
> and that discards the state automatically.
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