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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-752) Possible locking issues in HDFS Namenode
Date Tue, 28 Nov 2006 05:53:21 GMT
Possible locking issues in HDFS Namenode

                 Key: HADOOP-752
                 URL: http://issues.apache.org/jira/browse/HADOOP-752
             Project: Hadoop
          Issue Type: Bug
          Components: dfs
            Reporter: dhruba borthakur
         Assigned To: dhruba borthakur

I have been investigating the cause of random Namenode memory corruptions/memory overflows,
etc. Please comment.

 1. The functions datanodeReport() and DFSNodesStatus() do not acquire the global lock.
   This can race with another thread invoking registerDatanode(). registerDatanode()
   can remove a datanode (thru wipeDatanode()) while the datanodeReport thread is
   traversing the list of datanodes. This can cause exceptions to occur.

 2. The blocksMap is protected by the global lock. The setReplication() call does not acquire
   the global lock when it calls proccessOverReplicatedBlock(). This can cause corruption
in blockMap.

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