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From "Suresh Srinivas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-4182) SecondaryNameNode leaks NameCache entries
Date Tue, 13 Nov 2012 22:00:12 GMT

    [ https://issues.apache.org/jira/browse/HDFS-4182?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13496591#comment-13496591
] 

Suresh Srinivas commented on HDFS-4182:
---------------------------------------

bq. Ya I thought about disabling the NameCache, because it is not really needed. If you think
that would be less of an impact I am happy to switch over to that instead.
NameCache saves the memory used for repeated names in the namespace. Given most of the folks
use same JVM heap sizes for primary and secondary, the optimizations from NameCache may be
necessary. Secondary does not have block map related data and hence uses less java heap than
primary. Despite this leaving it as is probably a good idea.
                
> SecondaryNameNode leaks NameCache entries
> -----------------------------------------
>
>                 Key: HDFS-4182
>                 URL: https://issues.apache.org/jira/browse/HDFS-4182
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: name-node
>    Affects Versions: 0.23.4, 3.0.0, 2.0.2-alpha
>            Reporter: Todd Lipcon
>            Assignee: Robert Joseph Evans
>            Priority: Critical
>         Attachments: HDFS-4182.txt
>
>
> We recently saw an issue where a 2NN ran out of memory, even though it had a relatively
small fsimage. When we looked at the heap dump, we saw that all of the memory had gone to
entries in the NameCache.
> It appears that the NameCache is staying in "initializing" mode forever, and therefore
a long running 2NN leaks entries.

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