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https://issues.apache.org/jira/browse/HDFS-9958?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15262494#comment-15262494
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Daryn Sharp commented on HDFS-9958:
-----------------------------------
+1 Looks goods. Will file a followup for other improvements.
Regarding whether the client should pass the storage id or not, with the
current design it definitely should not. The client requests a block from the
datanode. The datanode serves from whatever storage it's on. Now let's say
the client thinks the block is on S1, but it's really on S3. The storage
cannot be honored. Only the DN should report the storage because it's
authoritative.
> 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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