[ https://issues.apache.org/jira/browse/HDFS-9313?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14976853#comment-14976853 ]
Ming Ma commented on HDFS-9313: ------------------------------- Thanks [~zhz]. If it continues, given no state has changed or no alternative approach is taken, it will just keep looping. > 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 > Assignee: Ming Ma > Attachments: HDFS-9313-2.patch, HDFS-9313.patch > > > 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. -- This message was sent by Atlassian JIRA (v6.3.4#6332)