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Date: Mon, 4 Dec 2006 14:33:22 -0800 (PST)
From: "dhruba borthakur (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Updated: (HADOOP-752) Possible locking issues in HDFS
 Namenode
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     [ http://issues.apache.org/jira/browse/HADOOP-752?page=all ]

dhruba borthakur updated HADOOP-752:
------------------------------------

    Attachment: namenodelocking.patch

Added locking to setReplication, datanodeReport & DFSNodesStatus

> 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
>         Attachments: namenodelocking.patch
>
>
> 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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