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https://issues.apache.org/jira/browse/MAPREDUCE-5812?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13974413#comment-13974413
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Jason Lowe commented on MAPREDUCE-5812:
---------------------------------------
Thanks for the patch, Mohammad. Speaking of backwards compatibility concerns,
I'd be a bit worried to call setupTask when we're not actually a task but an
AM, since we've never before called setupTask from the AM. Also we'd be
calling it before setupJob which is a change from prior behavior.
Since OutputCommitter is an abstract class I think it would be more
straightforward to implement proposal 1 which we can do in a
backwards-compatible way like this:
{code}
public abstract class OutputCommitter {
[...]
/**
* @deprecated Use {@link #isRecoverySupported(JobContext)} instead
*/
@Deprecated
public boolean isRecoverySupported() {
return false;
}
public boolean isRecoverySupported(JobContext jobContext) {
// default implementation calls original method for backwards-compatibility
return isRecoverySupported();
}
[...]
}
{code}
A custom committer can override the new method form and examine the
configuration available via the job context when making a recovery decision.
> Make task context available to OutputCommitter.isRecoverySupported()
> ---------------------------------------------------------------------
>
> Key: MAPREDUCE-5812
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5812
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: mr-am
> Affects Versions: 2.3.0
> Reporter: Mohammad Kamrul Islam
> Assignee: Mohammad Kamrul Islam
> Fix For: 2.5.0
>
> Attachments: MAPREDUCE-5812.1.patch
>
>
> Background
> ==========
> The system like Hive provides its version of OutputCommitter. The custom
> implementation of isRecoverySupported() requires task context. From
> taskContext:getConfiguration(), hive checks if hive-defined specific
> property is set or not. Based on the property value, it returns true or
> false. However, in the current OutputCommitter:isRecoverySupported(), there
> is no way of getting task config. As a result, user can't turn on/off the
> MRAM recovery feature.
> Proposed resolution:
> ===============
> 1. Pass Task Context into isRecoverySupported() method.
> Pros: Easy and clean
> Cons: Possible backward compatibility issue due to aPI changes. (Is it true?)
> 2. Call outputCommitter.setupTask(taskContext) from MRAM: The new
> OutputCommitter will store the context in the class level variable and use it
> from isRecoverySupported()
> Props: No API changes. No backward compatibility issue. This call can be made
> from MRAppMaster.getOutputCommitter() method for old API case.
> Cons: Might not be very clean solution due to class level variable.
> Please give your comments.
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