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https://issues.apache.org/jira/browse/MAPREDUCE-1648?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12855707#action_12855707
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Vinod K V commented on MAPREDUCE-1648:
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Sorry for overlooking this issue till far.
bq. When reviewing the patch, please test the performance and make sure we
don't re-introduce the slowness observed at HADOOP-1553.
This is a must.
Even before that, I don't think this approach will work at all when we consider
streaming and pipes jobs also. So far, we have been capturing stderr of
streaming tasks and stdout and stderr of pipes jobs into stdout/stderr files in
userlogs/$attemptid/. From the first look of the patch, it seems to me that
this behaviour is completely gone and the jvm's output and error are now being
redirected to /dev/null. The same behaviour for the subsequently spawned
streaming or pipes processes is expected but seems thrown away in this patch.
Even if we fix the above, I am not really sure this will solve the overall
feature of limiting logs simply because simply switching/rotating log files in
the jvm process will not do the same for the streaming/pipes tasks. I think the
approach outlined at MAPREDUCE-1100 for truncating logs after the tasks
finishes is the solutions given all these limitations. Thoughts?
> 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
> Attachments: syslog.patch
>
>
> 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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