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Date: Fri, 24 Jan 2014 15:06:37 +0000 (UTC)
From: "Buddy (JIRA)" <jira@apache.org>
To: hdfs-dev@hadoop.apache.org
Message-ID: <JIRA.12691050.1390575936558.7015.1390575997643@arcas>
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Subject: [jira] [Created] (HDFS-5828) BlockPlacementPolicyWithNodeGroup can
 place multiple replicas on the same node group when
 dfs.namenode.avoid.write.stale.datanode is true
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Buddy created HDFS-5828:
---------------------------

             Summary: BlockPlacementPolicyWithNodeGroup can place multiple replicas on the same node group when dfs.namenode.avoid.write.stale.datanode is true
                 Key: HDFS-5828
                 URL: https://issues.apache.org/jira/browse/HDFS-5828
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: namenode
    Affects Versions: 2.4.0
            Reporter: Buddy


When placing replicas using the replica placement policy BlockPlacementPolicyWithNodeGroup, the number of targets returned should be less than or equal to the number of node groups and no node group should get two replicas of the same block. The Junit test TestReplicationPolicyWithNodeGroup.testChooseMoreTargetsThanNodeGroups verifies this.

However, if the conf property "dfs.namenode.avoid.write.stale.datanode" is set to true, then block placement policy will return more targets than node groups when the number of replicas requested exceeds the number of node groups.

This can be seen by putting:
       CONF.setBoolean(DFS_NAMENODE_AVOID_STALE_DATANODE_FOR_WRITE_KEY, true);

in the setup method for TestReplicationPolicyWithNodeGroup. This will cause testChooseMoreTargetsThanNodeGroups to fail.


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