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From "Pete Wyckoff (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-3110) NameNode does logging in critical sections just about everywhere
Date Thu, 27 Mar 2008 21:15:24 GMT
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: 0.16.1, 0.16.0, 0.15.3, 0.15.2, 0.15.1, 0.15.0, 0.14.4, 0.14.3, 0.14.2,
0.14.1, 0.14.0
         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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