Kihwal Lee created HDFS-5010:
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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.
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