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From "Raghu Angadi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3110) NameNode does logging in critical sections just about everywhere
Date Thu, 27 Mar 2008 21:37:25 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3110?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12582798#action_12582798
] 

Raghu Angadi commented on HADOOP-3110:
--------------------------------------

Even if there are no benchmarks, any guesses as to order of improvement in NameNode performance
if we got rid of 50% of messages? 

> NameNode does logging in critical sections just about everywhere
> ----------------------------------------------------------------
>
>                 Key: HADOOP-3110
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3110
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: dfs
>    Affects Versions: 0.14.0, 0.14.1, 0.14.2, 0.14.3, 0.14.4, 0.15.0, 0.15.1, 0.15.2,
0.15.3, 0.16.0, 0.16.1
>         Environment: All
>            Reporter: Pete Wyckoff
>
> e.g., FSNameSystem.addStoredBlock (but almost every method has logging in its critical
sections)
> This method is synchronized and it's spitting something out to Log.info every block stored.
Normally not a big deal, but since this is in the name node and these are critical sections...
> We shouldn't even do any logging at all in critical sections, so even the info and warn
are bad.  But, in many places in the code, it would be hard to tease these out (although eventually
they really should be), but the system could start using something like an AsyncAppender and
see how it improves performance. 
> Even though the log may have a buffer, the writing and doing the formatting and stuff
cause a drag on performance with 100s/1000s of machines trying to talk to the name node.
> At a minimum, the most often  triggered Log.info could be changed to Log.debug.
> for reference: http://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/AsyncAppender.html

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