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https://issues.apache.org/jira/browse/FLINK-3089?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16323611#comment-16323611
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Bowen Li commented on FLINK-3089:
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[~xfournet] yes, supporting only TTL in processing time would be another
important assumption I'd like to make!
Implementing TTL in HeapStateBackend can be a bit tricky because of the number
of timers as you mentioned. W.r.t. development plan, I'm think we can probably
add the interface and support TTL in RocksDBStateBackend first. Then we can
decide 1) whether making it a RocksDBStateBackend-only feature, like
incremental checkpointing 2) if we should support TTL in HeapStateBackend, how
to implement it
What do you think?
cc [~srichter] [~aljoscha]
> State API Should Support Data Expiration (State TTL)
> ----------------------------------------------------
>
> 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
> Assignee: Bowen Li
>
> 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 state 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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