[jira] [Commented] (BEAM-115) Beam Runner API

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BEAM-115?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15344778#comment-15344778 ] 

ASF GitHub Bot commented on BEAM-115:
-------------------------------------

GitHub user kennknowles opened a pull request:

    https://github.com/apache/incubator-beam/pull/520

    [BEAM-115] Add ViewFn to SDK and adjust PCollectionView impls

    Be sure to do all of the following to help us incorporate your contribution
    quickly and easily:
    
     - [x] Make sure the PR title is formatted like:
       `[BEAM-<Jira issue #>] Description of pull request`
     - [x] Make sure tests pass via `mvn clean verify`. (Even better, enable
           Travis-CI on your fork and ensure the whole test matrix passes).
     - [x] Replace `<Jira issue #>` in the title with the actual Jira issue
           number, if there is one.
     - [x] If this contribution is large, please file an Apache
           [Individual Contributor License Agreement](https://www.apache.org/licenses/icla.txt).
    
    ---
    
    This is a small adjustment that reflects the language-independent architecture in the Java code, leaving the prior structure in place temporarily for ease of migration.
    


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

    $ git pull https://github.com/kennknowles/incubator-beam ViewFn

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

    https://github.com/apache/incubator-beam/pull/520.patch

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

    This closes #520
    
----
commit 56204137e4dbaaf1ea30770fb7927f27fa777805
Author: Kenneth Knowles <kl...@google.com>
Date:   2016-06-22T15:39:33Z

    Add ViewFn to SDK and adjust PCollectionView impls

----


> Beam Runner API
> ---------------
>
>                 Key: BEAM-115
>                 URL: https://issues.apache.org/jira/browse/BEAM-115
>             Project: Beam
>          Issue Type: Improvement
>          Components: runner-core
>            Reporter: Kenneth Knowles
>            Assignee: Kenneth Knowles
>
> The PipelineRunner API from the SDK is not ideal for the Beam technical vision.
> It has technical limitations:
>  - The user's DAG (even including library expansions) is never explicitly represented, so it cannot be analyzed except incrementally, and cannot necessarily be reconstructed (for example, to display it!).
>  - The flattened DAG of just primitive transforms isn't well-suited for display or transform override.
>  - The TransformHierarchy isn't well-suited for optimizations.
>  - The user must realistically pre-commit to a runner, and its configuration (batch vs streaming) prior to graph construction, since the runner will be modifying the graph as it is built.
>  - It is fairly language- and SDK-specific.
> It has usability issues (these are not from intuition, but derived from actual cases of failure to use according to the design)
>  - The interleaving of apply() methods in PTransform/Pipeline/PipelineRunner is confusing.
>  - The TransformHierarchy, accessible only via visitor traversals, is cumbersome.
>  - The staging of construction-time vs run-time is not always obvious.
> These are just examples. This ticket tracks designing, coming to consensus, and building an API that more simply and directly supports the technical vision.



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