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https://issues.apache.org/jira/browse/HDFS-5828?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13884251#comment-13884251
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Buddy commented on HDFS-5828:
-----------------------------
The reason that it was sometimes succeeding for me is that I was in the
debugger and the node was sometimes going stale (30 seconds). If the node is
not stale, then it always fails.
Also node that logNodeIsNotChosen does not actually log anything, it just
builds the message. The message is not logged in this case.
> 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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