Eugene Kirpichov created BEAM-1314:
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Summary: DoFn per-key lifecycle (Setup/Teardown)
Key: BEAM-1314
URL: https://issues.apache.org/jira/browse/BEAM-1314
Project: Beam
Issue Type: Improvement
Components: beam-model
Reporter: Eugene Kirpichov
Assignee: Frances Perry
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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