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