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From "Kuhu Shukla (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9958) BlockManager#createLocatedBlocks can throw NPE for corruptBlocks on failed storages.
Date Thu, 28 Apr 2016 18:45:12 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9958?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15262709#comment-15262709
] 

Kuhu Shukla commented on HDFS-9958:
-----------------------------------

[~brahmareddy] I am apprehensive of using an ArrayList instead of the plain array since when
I looked at an old thread for this code, it talked about how using lists will not be as fast.
I can try and dig that out.

> BlockManager#createLocatedBlocks can throw NPE for corruptBlocks on failed storages.
> ------------------------------------------------------------------------------------
>
>                 Key: HDFS-9958
>                 URL: https://issues.apache.org/jira/browse/HDFS-9958
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 2.7.2
>            Reporter: Kuhu Shukla
>            Assignee: Kuhu Shukla
>         Attachments: HDFS-9958-Test-v1.txt, HDFS-9958.001.patch, HDFS-9958.002.patch,
HDFS-9958.003.patch, HDFS-9958.004.patch, HDFS-9958.005.patch
>
>
> In a scenario where the corrupt replica is on a failed storage, before it is taken out
of blocksMap, there is a race which causes the creation of LocatedBlock on a {{machines}}
array element that is not populated. 
> Following is the root cause,
> {code}
> final int numCorruptNodes = countNodes(blk).corruptReplicas();
> {code}
> countNodes only looks at nodes with storage state as NORMAL, which in the case where
corrupt replica is on failed storage will amount to numCorruptNodes being zero. 
> {code}
> final int numNodes = blocksMap.numNodes(blk);
> {code}
> However, numNodes will count all nodes/storages irrespective of the state of the storage.
Therefore numMachines will include such (failed) nodes. The assert would fail only if the
system is enabled to catch Assertion errors, otherwise it goes ahead and tries to create LocatedBlock
object for that is not put in the {{machines}} array.
> Here is the stack trace:
> {code}
> java.lang.NullPointerException
> 	at org.apache.hadoop.hdfs.server.blockmanagement.DatanodeStorageInfo.toDatanodeInfos(DatanodeStorageInfo.java:45)
> 	at org.apache.hadoop.hdfs.server.blockmanagement.DatanodeStorageInfo.toDatanodeInfos(DatanodeStorageInfo.java:40)
> 	at org.apache.hadoop.hdfs.protocol.LocatedBlock.<init>(LocatedBlock.java:84)
> 	at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.createLocatedBlock(BlockManager.java:878)
> 	at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.createLocatedBlock(BlockManager.java:826)
> 	at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.createLocatedBlockList(BlockManager.java:799)
> 	at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.createLocatedBlocks(BlockManager.java:899)
> 	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getBlockLocationsInt(FSNamesystem.java:1849)
> 	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getBlockLocations(FSNamesystem.java:1799)
> 	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getBlockLocations(FSNamesystem.java:1712)
> 	at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.getBlockLocations(NameNodeRpcServer.java:588)
> 	at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.getBlockLocations(ClientNamenodeProtocolServerSideTranslatorPB.java:365)
> 	at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
> 	at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:616)
> 	at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:982)
> 	at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2049)
> 	at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2045)
> 	at java.security.AccessController.doPrivileged(Native Method)
> 	at javax.security.auth.Subject.doAs(Subject.java:415)
> 	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)
> 	at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2043)
> {code}



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