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Date: Wed, 21 Apr 2010 23:26:49 -0400 (EDT)
From: "Guilin Sun (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Subject: [jira] Updated: (MAPREDUCE-1648) Use rolling to limit tasklogs
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     [ https://issues.apache.org/jira/browse/MAPREDUCE-1648?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Guilin Sun updated MAPREDUCE-1648:
----------------------------------

     Original Estimate: 0h
    Remaining Estimate: 0h
              Priority: Major  (was: Minor)

That's great!
Currentlly, this patch was already through QA, I am going to attach design document first this week.
Thank you, Vinod!

> Use rolling to limit tasklogs
> -----------------------------
>
>                 Key: MAPREDUCE-1648
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1648
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: tasktracker
>            Reporter: Guilin Sun
>         Attachments: syslog.patch
>
>   Original Estimate: 0h
>  Remaining Estimate: 0h
>
> There are at least two types of task-logs: syslog and stdlog
> Task-Jvm outputs syslog by log4j with TaskLogAppender, TaskLogAppender looks just like "tail -c", it stores last N byte/line logs in memory(via queue), and do real output only if all logs is commit and Appender is going to close.
> The common problem of TaskLogAppender and 'tail -c'  is keep everything in memory and user can't see any log output while task is in progress.
> So I'm going to try RollingFileAppender  instead of  TaskLogAppender, use MaxFileSize&MaxBackupIndex to limit log file size.
> RollingFileAppender is also suitable for stdout/stderr, just redirect stdout/stderr to log4j via LoggingOutputStream, no client code have to be changed, and RollingFileAppender seems better than 'tail -c' too.

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