[jira] [Commented] (BEAM-175) Leak garbage collection timers in GlobalWindow

["Mark Shields (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BEAM-175?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15227290#comment-15227290 ] 

Mark Shields commented on BEAM-175:
-----------------------------------

Extra problem, for no extra cost:
In the global window we dutifully increment the pane index for each successive pane.
So even if we fix the timer problem we still have state-per-key-till-end-of-time.

Thankfully we don't store 'false' in the trigger finished bits, so we don't have to worry about that for Repeatedly triggers. 

> Leak garbage collection timers in GlobalWindow
> ----------------------------------------------
>
>                 Key: BEAM-175
>                 URL: https://issues.apache.org/jira/browse/BEAM-175
>             Project: Beam
>          Issue Type: Bug
>          Components: runner-core
>            Reporter: Mark Shields
>            Assignee: Mark Shields
>
> Consider the  transform:
>   Window
>     .into(new GlobalWindows())
>     .triggering(
>       Repeatedly.forever(
>         AfterProcessingTime.pastFirstElementInPane().plusDelayOf(...)))
>     .discardingFiredPanes()
> This is a common idiom for 'process elements bunched by arrival time'.
> Currently we create an end-of-window timer per key, which clearly will only fire if the pipeline is drained.
> Better would be to avoid creating end-of-window timers if there's no state which needs to be processed at end-of-window (ie at drain if the Global window).



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