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https://issues.apache.org/jira/browse/HDFS-5010?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kihwal Lee updated HDFS-5010:
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Attachment: HDFS-5010.patch
HDFS-5010.b023.patch
The new patches also removes the getCurrentUser() call during block token
generation. BlockTokenSecretManager already has a method that accepts user
name. I made BlockManager call FSNamesystem.getRemoteUser() and pass the short
name to the method. Balancer also generates block tokens, but the cached UGI
won't be used since it is not part of RPC service.
> Reduce the frequency of getCurrentUser() calls from namenode
> ------------------------------------------------------------
>
> Key: HDFS-5010
> URL: https://issues.apache.org/jira/browse/HDFS-5010
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode, performance
> Affects Versions: 2.1.0-beta, 0.23.9
> Reporter: Kihwal Lee
> Assignee: Kihwal Lee
> Attachments: HDFS-5010.b023.patch, HDFS-5010.patch, HDFS-5010.patch
>
>
> According to the "worst" jstack of a busy namenode I took, there were 29
> BLOCKED handler threads. All of them were blocked on the UGI class lock. Here
> is the breakdown:
> - 2 ensureInitialized() - from non static synchronized methods. HADOOP-9748
> will unblock these.
> - 27 getCurrentUser()
> Among the 27 threads that were blocked at getCurrentUser(),
> - 18 FSPermissionChecker() - from FSNamesystem#getPermissionChecker() in most
> namenode RPC methods
> - 8 BlockTokenSecretManager#generateToken() - getBlockLocations()
> - 1 NameNodeRpcServer.mkdirs
> I think FSPermissionChecker can be modified to be created with a passed in
> UGI. FSNamesystem can the one already stored in RPC server by calling
> getRemoteUser(). This will eliminate a bulk of getCurrentUser() calls from
> namenode RPC handlers. A similar change can be made to mkdirs. Block token
> generation is not as straightforward. Even without it we can eliminate
> majority of the calls.
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