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Posted to commits@beam.apache.org by "Ryan Skraba (JIRA)" <ji...@apache.org> on 2016/12/22 16:46:58 UTC

[jira] [Created] (BEAM-1206) PCollections used as a sideInput are unnecessarily re-evaluated.

Ryan Skraba created BEAM-1206:
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             Summary: PCollections used as a sideInput are unnecessarily re-evaluated.
                 Key: BEAM-1206
                 URL: https://issues.apache.org/jira/browse/BEAM-1206
             Project: Beam
          Issue Type: Bug
          Components: runner-spark
    Affects Versions: 0.4.0-incubating
            Reporter: Ryan Skraba
            Assignee: Amit Sela


The SparkRunner keeps track of "leaf" transforms in the job graph and ensures that they have been executed when the pipeline is run.

However, when a PCollection is used as a sideInput, it is evaluated *once* to get the materialized values but is still considered a leaf node.  It is evaluated a second time at the end of the Spark job, which is unnecessary (and can cause unexpected behaviour).

One of the symptoms of this bug is that `Sink`s will create spurious writers that execute, but are never finalized.  Specifically the HDFSFileSink will _always_ die with a `Writer results and output files do not match` error.



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