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https://issues.apache.org/jira/browse/HADOOP-9749?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13713803#comment-13713803
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Kihwal Lee commented on HADOOP-9749:
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I think this will be less critical for namenode with HDFS-5010. Other RPC
servers will still benefit.
> Remove synchronization for UGI.getCurrentUser
> ---------------------------------------------
>
> Key: HADOOP-9749
> URL: https://issues.apache.org/jira/browse/HADOOP-9749
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: security
> Affects Versions: 0.23.0, 2.0.0-alpha, 3.0.0
> Reporter: Daryn Sharp
> Assignee: Daryn Sharp
> Priority: Critical
>
> HADOOP-7854 added synchronization to {{getCurrentUser}} due to
> {{ConcurrentModificationExceptions}}. This degrades NN call handler
> performance.
> The problem was not well understood at the time, but it's caused by a
> collision between relogin and {{getCurrentUser}} due to a bug in
> {{Krb5LoginModule}}. Avoiding the collision will allow removal of the
> synchronization.
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