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https://issues.apache.org/jira/browse/MAPREDUCE-2506?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13035065#comment-13035065
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Owen O'Malley commented on MAPREDUCE-2506:
------------------------------------------
This patch creates a ContextFactory class that provides two functions:
{code}
public static JobContext cloneContext(JobContext original,
Configuration conf
) throws IOException,
InterruptedException;
public static <K1,V1,K2,V2> Mapper<K1,V1,K2,V2>.Context
cloneMapContext(MapContext<K1,V1,K2,V2> context,
Configuration conf,
RecordReader<K1,V1> reader,
RecordWriter<K2,V2> writer
) throws IOException, InterruptedException;
{code}
This first clones JobContexts, TaskAttemptContexts, and MapContexts. The
contexts are the same, except they have a new configuration.
The second method allows additional hooks to replace the reader and writer for
the context.
> Create a compatible interface for frameworks that need to clone MapReduce
> context objects.
> ------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-2506
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-2506
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Reporter: Owen O'Malley
> Attachments: ContextFactory.java, ContextFactory.java, mr-2506.patch
>
>
> In 0.21 we moved the org.apache.hadoop.mapreduce context objects to
> interfaces.
> That made the APIs much better, but broke backwards compatibility for
> frameworks that need to clone them.
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