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From "Alejandro Abdelnur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1558) changes to OutputFormat to work on temporary directory to enable re-running crashed jobs (Issue: 1121)
Date Thu, 09 Aug 2007 07:55:43 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1558?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12518653

Alejandro Abdelnur commented on HADOOP-1558:

A comment related 1416.

1558 issue/patch is to address the handling of the output directory from working to final

1416 issue is to address the handling of the output of a part from working to final location
with speculative execution considerations.

The OutputHandler (of 1558) provides to the task the base path where to create the part file.

To solve 1416 a similar pattern (of 1558) could be used.

A way of doing it could be by adding to the OutputHandler interface the following methods:

  Path getUncommittedPartFile(JobConf conf, taskId);
  void initializePartFile(JobConf conf, taskId);
  void commitPartFile(JobConf conf, taskId);

The speculative execution logic would invoke init/commit methods and this methods would resolve
any cleanup/discard to be done.

As this is handled in the OutputHandler implementation it will work for non-file base scenarios
as well and transparently from the TT.

> changes to OutputFormat to work on temporary directory to enable re-running crashed jobs
(Issue: 1121)
> ------------------------------------------------------------------------------------------------------
>                 Key: HADOOP-1558
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1558
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: mapred
>         Environment: all
>            Reporter: Alejandro Abdelnur
>             Fix For: 0.15.0
>         Attachments: hadoop-1558-JUL2607-1600.txt
> Add  OutputFormat methods like:
> /** Called to initialize output for this job. */
> void initialize(JobConf job) throws IOException;
> /** Called to finalize output for this job. */
> void commit(JobConf job) throws IOException;
> In the base implemenation for FileSystem output, initialize() might then create a temporary
directory for the job, removing any that already exists, and commit could rename the temporary
output directory to the final name. 
> The existing checkOutputSpecs() would continue to throw an exception if the final output
already exists.

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