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https://issues.apache.org/jira/browse/FLINK-4415?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aljoscha Krettek updated FLINK-4415:
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Assignee: Kostas Kloudas
> Enhance Trigger Interface with onFire() and onCleanup()
> -------------------------------------------------------
>
> Key: FLINK-4415
> URL: https://issues.apache.org/jira/browse/FLINK-4415
> Project: Flink
> Issue Type: Sub-task
> Components: Streaming
> Reporter: Aljoscha Krettek
> Assignee: Kostas Kloudas
>
> Currently, when a {{Trigger}} returns {{PURGE}} (or {{FIRE_AND_PURGE}}) the
> window state, trigger state and timer state are completely deleted. Some use
> cases might only want to have the window contents deleted. In addition,
> triggers have no way of reacting to garbage collection, i.e. the time when
> allowed lateness expires and we completely clean up everything.
> I want to propose to add these two new methods:
> {code}
> void onFire(...)
> boolean onCleanup(...)
> {code}
> The {{onFire()}} is called when a window fires and we emit data. This gives
> the trigger the chance to reset/cleanup state. {{onCleanup()}} gives the
> trigger the chance to emit one final result before everything is purged, and
> also allows to cleanup data, i.e. it also replaces {{clear()}}. The window
> operator will not purge window state and timers anymore but call
> {{Trigger.onFire()}} to give it a chance to decide whether to delete state
> and timers.
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