[jira] [Created] (BEAM-801) SplittableParDo must be a pseudo-primitive, not ParDo(OldDoFn)

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

Kenneth Knowles created BEAM-801:
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             Summary: SplittableParDo must be a pseudo-primitive, not ParDo(OldDoFn)
                 Key: BEAM-801
                 URL: https://issues.apache.org/jira/browse/BEAM-801
             Project: Beam
          Issue Type: Bug
          Components: runner-core, runner-direct
            Reporter: Kenneth Knowles


Today, runners-core contains an expansion of {{ParDo(DoFn)}} that implements it via unsupported features of {{ParDo(OldDoFn)}}. This expansion is used by the DirectRunner.

The right approach to provide a ready implementation in runners-core is the one taken by {{GroupAlsoByWindowViaWindowSetDoFn}} where the unsupported features are provided to the constructor of the {{DoFn}}, rather than expected to be passed through the {{ProcessContext}}.

These features are not guaranteed to be part of the public state & timers API of {{DoFn}}, particularly in the case of watermark holds, so it is not prudent to plan on waiting for the new state & timers API and porting over.

These issues create real blockers by causing dependency cycles between implementing {{DoFn}} fully (requires no use of unsupported features), implementing new state and timers (requires new {{DoFn}}), and keeping the hack until new {{DoFn}} has state and timers (requires use of unsupported features).

To break the cycle, the tests that rely on unsupported features are being disabled. They can be re-enabled either by following the design suggested above (probably the most robust approach) or by waiting and porting to new features as they are available.



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