Thomas Groh created BEAM-452:
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Summary: Implement DoFn per-instance setup and teardown methods
Key: BEAM-452
URL: https://issues.apache.org/jira/browse/BEAM-452
Project: Beam
Issue Type: Bug
Components: runner-dataflow, runner-direct, runner-flink,
runner-spark, sdk-java-core
Reporter: Thomas Groh
Assignee: Thomas Groh
https://docs.google.com/document/d/1LLQqggSePURt3XavKBGV7SZJYQ4NW8yCu63lBchzMRk/edit
BEAM-38 permits DoFns to be reused across bundles. DoFn instances may need to
do per-instance setup and teardown, and to avoid redoing the work per-bundle,
the system should provide hooks to call before a DoFn is first used and after
it will no longer be used.
DoFn#setup is called before any other calls to DoFn methods. DoFn#teardown is
called after any method throws an exception, or when the runner will no longer
use a DoFn instance (e.g. when it evicts it from a cache).
Runners must call these methods appropriately in all cases (including if a DoFn
is used exactly once, for a single bundle, and discarded).
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