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https://issues.apache.org/jira/browse/HDFS-8770?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15002599#comment-15002599
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Xiao Chen commented on HDFS-8770:
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Hi [~aderen],
Thanks for reporting the issue and providing a patch. The fix makes sense to me.
Could you add a unit test to reproduce the scenario that you're trying to fix?
> ReplicationMonitor thread received Runtime exception: NullPointerException
> when BlockManager.chooseExcessReplicates
> -------------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-8770
> URL: https://issues.apache.org/jira/browse/HDFS-8770
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 2.6.0, 2.7.0
> Reporter: ade
> Assignee: ade
> Priority: Critical
> Attachments: HDFS-8770_v1.patch
>
>
> Namenode shutdown when ReplicationMonitor thread received Runtime exception:
> {quote}
> 2015-07-08 16:43:55,167 ERROR
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager:
> ReplicationMonitor thread received Runtime exception.
> java.lang.NullPointerException
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy.adjustSetsWithChosenReplica(BlockPlacementPolicy.java:189)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.chooseExcessReplicates(BlockManager.java:2911)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.processOverReplicatedBlock(BlockManager.java:2849)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.processMisReplicatedBlock(BlockManager.java:2780)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.rescanPostponedMisreplicatedBlocks(BlockManager.java:1931)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager$ReplicationMonitor.run(BlockManager.java:3628)
> at java.lang.Thread.run(Thread.java:744)
> {quote}
> We use hadoop-2.6.0 configured with heterogeneous storages and
> setStoragePolicy some path One_SSD. When a block has excess replicated like 2
> SSD replica on different rack(exactlyOne set) and 2 Disk on same
> rack(moreThanOne set), BlockPlacementPolicyDefault.chooseReplicaToDelete
> return null because only moreThanOne set be chosen to find SSD replica
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