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https://issues.apache.org/jira/browse/PIG-3419?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13747131#comment-13747131
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Mark Wagner commented on PIG-3419:
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I'd also be in favor putting this in trunk as opposed to a Tez branch. Although
the motivation for this is Tez, I think we would want this patch in Pig even if
there wasn't Tez support.
A couple short comments for Achal:
* It looks like the build targets that include the META-INF are only executed
when building against hadoopversion=23. The META-INF also don't seem to be
included in the pig.jar and pig-withouthadoop.jar that go in the root
directory. I tried copying in the correct jars, but it seems like something is
still off.
* The changes to the try/catch blocks in MapReduceLauncher break on 23, because
HadoopShims for 23 doesn't throw an exception where 20 does. Maybe that should
be fixed in HadoopShims though.
> Pluggable Execution Engine
> ---------------------------
>
> Key: PIG-3419
> URL: https://issues.apache.org/jira/browse/PIG-3419
> Project: Pig
> Issue Type: New Feature
> Affects Versions: 0.12
> Reporter: Achal Soni
> Assignee: Achal Soni
> Priority: Minor
> Attachments: execengine.patch, finalpatch.patch,
> mapreduce_execengine.patch, stats_scriptstate.patch, test_suite.patch
>
>
> In an effort to adapt Pig to work using Apache Tez
> (https://issues.apache.org/jira/browse/TEZ), I made some changes to allow for
> a cleaner ExecutionEngine abstraction than existed before. The changes are
> not that major as Pig was already relatively abstracted out between the
> frontend and backend. The changes in the attached commit are essentially the
> barebones changes -- I tried to not change the structure of Pig's different
> components too much. I think it will be interesting to see in the future how
> we can refactor more areas of Pig to really honor this abstraction between
> the frontend and backend.
> Some of the changes was to reinstate an ExecutionEngine interface to tie
> together the front end and backend, and making the changes in Pig to delegate
> to the EE when necessary, and creating an MRExecutionEngine that implements
> this interface. Other work included changing ExecType to cycle through the
> ExecutionEngines on the classpath and select the appropriate one (this is
> done using Java ServiceLoader, exactly how MapReduce does for choosing the
> framework to use between local and distributed mode). Also I tried to make
> ScriptState, JobStats, and PigStats as abstract as possible in its current
> state. I think in the future some work will need to be done here to perhaps
> re-evaluate the usage of ScriptState and the responsibilities of the
> different statistics classes. I haven't touched the PPNL, but I think more
> abstraction is needed here, perhaps in a separate patch.
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