Buddy created HDFS-5828:
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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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