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From "Ming Ma (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-9313) Possible NullPointerException in BlockManager if no excess replica can be chosen
Date Tue, 27 Oct 2015 00:26:27 GMT
Ming Ma created HDFS-9313:
-----------------------------

             Summary: Possible NullPointerException in BlockManager if no excess replica can
be chosen
                 Key: HDFS-9313
                 URL: https://issues.apache.org/jira/browse/HDFS-9313
             Project: Hadoop HDFS
          Issue Type: Bug
            Reporter: Ming Ma


HDFS-8647 makes it easier to reason about various block placement scenarios. Here is one possible
case where BlockManager won't be able to find the excess replica to delete: when storage policy
changes around the same time balancer moves the block. When this happens, it will cause NullPointerException.

{noformat}
java.lang.NullPointerException
	at org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy.adjustSetsWithChosenReplica(BlockPlacementPolicy.java:156)
	at org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseReplicasToDelete(BlockPlacementPolicyDefault.java:978)
{noformat}

Note that it isn't found in any production clusters. Instead, it is found from new unit tests.
In addition, the issue has been there before HDFS-8647.





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