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https://issues.apache.org/jira/browse/HDFS-14081?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16687526#comment-16687526
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Xiao Chen commented on HDFS-14081:
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Thanks [~shwetayakkali] for the patch and [~kihwal] for the suggestion.
Please don't set Fix Versions - it's supposed to be used by committers to
reflect which branch a patch is actually checked in.
[~kihwal]'s suggestion makes sense - some queues only make sense for ANN, we
may as well bump FSN#metaSave to be active-only. Though I'm not sure that is
what we see here exactly (and the NPE itself feels it warrants some
improvement) ...
When discussing with [~shwetayakkali], one part of code I found interesting is
{{BlockManager#rescanPostponedMisreplicatedBlocks}} checks {{BlockInfo}}
nullity, where {{BlockManager#dumpBlockMeta}} does not. They're all protected
by FSN write locks, but the missing null check seemed like a bug. Please let me
know if I missed anything.
> hdfs dfsadmin -metasave metasave_test results NPE
> -------------------------------------------------
>
> Key: HDFS-14081
> URL: https://issues.apache.org/jira/browse/HDFS-14081
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: hdfs
> Affects Versions: 3.2.1
> Reporter: Shweta
> Assignee: Shweta
> Priority: Major
> Attachments: HDFS-14081.001.patch
>
>
> Race condition is encountered while adding Block to
> postponedMisreplicatedBlocks which in turn tried to retrieve Block from
> BlockManager in which it may not be present.
> This happens in HA, metasave in first NN succeeded but failed in second NN,
> StackTrace showing NPE is as follows:
> {code}
> 2018-07-12 21:39:09,783 WARN org.apache.hadoop.ipc.Server: IPC Server handler
> 24 on 8020, call Call#1 Retry#0
> org.apache.hadoop.hdfs.protocol.ClientProtocol.metaSave from
> 172.26.9.163:602342018-07-12 21:39:09,783 WARN org.apache.hadoop.ipc.Server:
> IPC Server handler 24 on 8020, call Call#1 Retry#0
> org.apache.hadoop.hdfs.protocol.ClientProtocol.metaSave from
> 172.26.9.163:60234java.lang.NullPointerException at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.chooseSourceDatanodes(BlockManager.java:2175)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.dumpBlockMeta(BlockManager.java:830)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.metaSave(BlockManager.java:762)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.metaSave(FSNamesystem.java:1782)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.metaSave(FSNamesystem.java:1766)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.metaSave(NameNodeRpcServer.java:1320)
> at
> org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.metaSave(ClientNamenodeProtocolServerSideTranslatorPB.java:928)
> at
> org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
> at
> org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:523)
> at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:991) at
> org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:869) at
> org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:815) 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:1685)
> at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2675) {code}
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