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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (BEAM-1925) Make DoFn invocation logic of Python SDK more extensible
Date Mon, 08 May 2017 20:47:04 GMT

    [ https://issues.apache.org/jira/browse/BEAM-1925?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16001496#comment-16001496
] 

ASF GitHub Bot commented on BEAM-1925:
--------------------------------------

Github user sb2nov closed the pull request at:

    https://github.com/apache/beam/pull/2848


> Make DoFn invocation logic of Python SDK more extensible
> --------------------------------------------------------
>
>                 Key: BEAM-1925
>                 URL: https://issues.apache.org/jira/browse/BEAM-1925
>             Project: Beam
>          Issue Type: Improvement
>          Components: sdk-py
>            Reporter: Chamikara Jayalath
>            Assignee: Chamikara Jayalath
>
> DoFn invocation logic of Python SDK is currently in DoFnRunner class.
> https://github.com/apache/beam/blob/master/sdks/python/apache_beam/runners/common.py#L54
> At initialization of this, we parse a DoFn and create local state. We use this state
when invoking DoFn methods process, start_bundle, and finish_bundle. For example, we store
a list of  ArgPlaceholder objects within the state of DoFnRunner to facilitate invocation
of process method.
> We will need to extend this functionality when adding new features to DoFn class (for
example to support Splittable DoFn [1]). So I think it's good to refactor this code to be
more extensible. 
> I think a good approach for this is to add DoFnInvoker and DoFnSignature classes similar
to Java SDK [2].
> In this approach:
> A DoFnSignature captures the signature of a DoFn including methods and arguments.
> A DoFnInvoker implements a particular way DoFn methods will be executed (initially we'll
have simple and per-window invokers [3]).
> A runner uses DoFnRunner to execute methods of a given DoFn. At initialization, DoFnRunner
crates a DoFnSignature and a DoFnInvoker for the given DoFn.
> DoFnSignature and DoFnInvoker methods will be used by SplittableDoFn implementation as
well. 
> [1] https://docs.google.com/document/d/1h_zprJrOilivK2xfvl4L42vaX4DMYGfH1YDmi-s_ozM/edit#heading=h.e6patunrpiql
> [2]https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/reflect/DoFnSignature.java
> [3] https://github.com/apache/beam/blob/master/sdks/python/apache_beam/runners/common.py#L200



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