[jira] [Commented] (BEAM-260) Know the getSideInputWindow upper bound so can gc side input state

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

    [ https://issues.apache.org/jira/browse/BEAM-260?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15275128#comment-15275128 ] 

Aljoscha Krettek commented on BEAM-260:
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I thought about this as well while working on the Flink Streaming side input support. Could it be enough to have something like {{WindowFn.getSideInputCleanupTime(BoundedWindow)}} that tells you when you can GC a side input window based on the main-input watermark. This would be called on the WindowFn of the side input, since it knows how the main-input windows are mapped to side inputs.

> Know the getSideInputWindow upper bound so can gc side input state
> ------------------------------------------------------------------
>
>                 Key: BEAM-260
>                 URL: https://issues.apache.org/jira/browse/BEAM-260
>             Project: Beam
>          Issue Type: Bug
>          Components: beam-model
>            Reporter: Mark Shields
>            Assignee: Frances Perry
>
> We currently have no static knowledge about the getSideInputWindow function, and runners are thus forced to hold on to all side input state / elements in case a future element reaches back into an earlier side input element.
> Maybe we need an upper bound on lag from current to result of getSideInputWindow so we can have a progressing gc horizon as we do for  GKB window state. 



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