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https://issues.apache.org/jira/browse/HDFS-10715?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15405391#comment-15405391
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Guangbin Zhu commented on HDFS-10715:
-------------------------------------
Thanks Akira, I'll fix it and submit another patch.
> NPE when applying AvailableSpaceBlockPlacementPolicy
> ----------------------------------------------------
>
> Key: HDFS-10715
> URL: https://issues.apache.org/jira/browse/HDFS-10715
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 2.8.0
> Environment: cdh5.8.0
> Reporter: Guangbin Zhu
> Attachments: HDFS-10715.001.patch, HDFS-10715.002.patch
>
>
> As HDFS-8131 introduced an AvailableSpaceBlockPlacementPolicy, but In some
> cases, it caused NPE.
> Here are my namenode daemon logs :
> 2016-08-02 13:05:03,271 WARN org.apache.hadoop.ipc.Server: IPC Server handler
> 13 on 8020, call org.apache.hadoop.hdfs.protocol.ClientProtocol.addBlock from
> 10.132.89.79:14001 Call#56 Retry#0
> java.lang.NullPointerException
> at
> org.apache.hadoop.hdfs.server.blockmanagement.AvailableSpaceBlockPlacementPolicy.compareDataNode(AvailableSpaceBlockPlacementPolicy.java:95)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.AvailableSpaceBlockPlacementPolicy.chooseDataNode(AvailableSpaceBlockPlacementPolicy.java:80)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseRandom(BlockPlacementPolicyDefault.java:691)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseRandom(BlockPlacementPolicyDefault.java:665)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseLocalRack(BlockPlacementPolicyDefault.java:572)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseTargetInOrder(BlockPlacementPolicyDefault.java:457)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseTarget(BlockPlacementPolicyDefault.java:367)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseTarget(BlockPlacementPolicyDefault.java:242)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseTarget(BlockPlacementPolicyDefault.java:114)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseTarget(BlockPlacementPolicyDefault.java:130)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.chooseTarget4NewBlock(BlockManager.java:1606)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:3315)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.addBlock(NameNodeRpcServer.java:679)
> at
> org.apache.hadoop.hdfs.server.namenode.AuthorizationProviderProxyClientProtocol.addBlock(AuthorizationProviderProxyClientProtocol.java:214)
> at
> org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.addBlock(ClientNamenodeProtocolServerSideTranslatorPB.java:489)
> at
> org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
> at
> org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:617)
> at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:1073)
> at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2086)
> at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2082)
> at java.security.AccessController.doPrivileged(Native Method)
> at javax.security.auth.Subject.doAs(Subject.java:422)
> at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1693)
> at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2080)
> I reviewed the source code, and found the bug in method chooseDataNode.
> clusterMap.chooseRandom may return null, which cannot compare using equals
> a.equals(b) method.
> Though this exception can be caught, and then retry another call. I think
> this bug should be fixed.
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