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From "Koji Noguchi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1648) Use RollingFileAppender to limit tasklogs
Date Tue, 06 Apr 2010 16:37:39 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1648?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12854051#action_12854051

Koji Noguchi commented on MAPREDUCE-1648:

When reviewing the patch, please test the performance and make sure we don't re-introduce
the slowness observed at HADOOP-1553.

> Use RollingFileAppender 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
>            Priority: Minor
> 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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