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From "ASF GitHub Bot (JIRA)" <>
Subject [jira] [Commented] (BEAM-1316) DoFn#startBundle should not be able to output
Date Wed, 26 Apr 2017 01:22:04 GMT


ASF GitHub Bot commented on BEAM-1316:

GitHub user tgroh opened a pull request:

    [BEAM-1316] Forbid output in StartBundle

    Be sure to do all of the following to help us incorporate your contribution
    quickly and easily:
     - [ ] Make sure the PR title is formatted like:
       `[BEAM-<Jira issue #>] Description of pull request`
     - [ ] Make sure tests pass via `mvn clean verify`. (Even better, enable
           Travis-CI on your fork and ensure the whole test matrix passes).
     - [ ] Replace `<Jira issue #>` in the title with the actual Jira issue
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     - [ ] If this contribution is large, please file an Apache
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    TODO: Add comments, audit any other context creation.

You can merge this pull request into a Git repository by running:

    $ git pull no_start_bundle_output

Alternatively you can review and apply these changes as the patch at:

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #2695
commit 5d369da267405911e534e49ad74fdb64bc2c3150
Author: Thomas Groh <>
Date:   2017-04-26T01:20:21Z

    Forbid output in StartBundle


> DoFn#startBundle should not be able to output
> ---------------------------------------------
>                 Key: BEAM-1316
>                 URL:
>             Project: Beam
>          Issue Type: Bug
>          Components: sdk-java-core
>            Reporter: Thomas Groh
>            Assignee: Thomas Groh
>             Fix For: First stable release
> While within startBundle and finishBundle, the window in which elements are output is
not generally defined. Elements must always be output from within a windowed context, or the
{{WindowFn}} used by the {{PCollection}} may not operate appropriately.
> startBundle and finishBundle are suitable for operational duties, similarly to {{setup}}
and {{teardown}}, but within the scope of some collection of input elements. This includes
actions such as clearing field state within a DoFn and ensuring all live RPCs complete successfully
before committing inputs.
> Sometimes it might be reasonable to output from {{@FinishBundle}} but it is hard to imagine
a situation where output from {{@StartBundle}} is useful in a way that doesn't seriously abuse

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