[jira] [Commented] (BEAM-1314) DoFn per-key lifecycle (Setup/Teardown)

["Kenneth Knowles (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BEAM-1314?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17546269#comment-17546269 ] 

Kenneth Knowles commented on BEAM-1314:
---------------------------------------

This issue has been migrated to https://github.com/apache/beam/issues/18150

> DoFn per-key lifecycle (Setup/Teardown)
> ---------------------------------------
>
>                 Key: BEAM-1314
>                 URL: https://issues.apache.org/jira/browse/BEAM-1314
>             Project: Beam
>          Issue Type: Wish
>          Components: beam-model
>            Reporter: Eugene Kirpichov
>            Priority: P3
>
> DoFn's that use state and timers are implicitly per-key. Setup/Teardown methods are usually used to establish expensive resources - long-standing connections and such.
> For per-key DoFn's, we'd often want to use these per-key, so it'd be good to have ability in the model to ask that there be 1 instance of the DoFn per key, reused between e.g. different timer or trigger firings for this key, but not used for other keys.
> E.g. this would be particularly useful for Splittable DoFn - for its ability to reuse expensive resources between checkpoints.



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