[jira] [Created] (HDFS-5010) Reduce the frequency of getCurrentUser() calls from namenode

["Kihwal Lee (JIRA)" <ji...@apache.org>]

Kihwal Lee created HDFS-5010:
--------------------------------

             Summary: 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
            Reporter: Kihwal Lee


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. This Jira 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.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira