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https://issues.apache.org/jira/browse/HDFS-11225?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15735270#comment-15735270
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Wei-Chiu Chuang commented on HDFS-11225:
----------------------------------------
Thanks [~linyiqun] for confirming this issue. Yes I think this is by design an
issue since snapshot was introduced in 2.4, and we've observed the same
incidence on multiple version of CDH. Have you dig into it and want to
contribute a patch?
> NameNode crashed because deleteSnapshot held FSNamesystem lock too long
> -----------------------------------------------------------------------
>
> Key: HDFS-11225
> URL: https://issues.apache.org/jira/browse/HDFS-11225
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 2.4.0
> Environment: CDH5.8.2
> Reporter: Wei-Chiu Chuang
> Priority: Critical
> Labels: high-availability
>
> The deleteSnapshot operation is synchronous. In certain situations this
> operation may hold FSNamesystem lock for too long, bringing almost every
> NameNode operation to a halt.
> We have observed one incidence where it took so long that ZKFC believes the
> NameNode is down. All other IPC threads were waiting to acquire FNamesystem
> lock.
> Relevant log:
> {noformat}
> Thread 154 (IPC Server handler 86 on 8020):
> State: RUNNABLE
> Blocked count: 2753455
> Waited count: 89201773
> Stack:
>
> org.apache.hadoop.hdfs.server.namenode.INode$BlocksMapUpdateInfo.addDeleteBlock(INode.java:879)
>
> org.apache.hadoop.hdfs.server.namenode.INodeFile.destroyAndCollectBlocks(INodeFile.java:508)
>
> org.apache.hadoop.hdfs.server.namenode.INodeDirectory.destroyAndCollectBlocks(INodeDirectory.java:763)
>
> org.apache.hadoop.hdfs.server.namenode.INodeDirectory.destroyAndCollectBlocks(INodeDirectory.java:763)
>
> org.apache.hadoop.hdfs.server.namenode.INodeDirectory.destroyAndCollectBlocks(INodeDirectory.java:763)
>
> org.apache.hadoop.hdfs.server.namenode.INodeDirectory.destroyAndCollectBlocks(INodeDirectory.java:763)
>
> org.apache.hadoop.hdfs.server.namenode.INodeReference.destroyAndCollectBlocks(INodeReference.java:339)
>
> org.apache.hadoop.hdfs.server.namenode.INodeReference$WithName.destroyAndCollectBlocks(INodeReference.java:606)
>
> org.apache.hadoop.hdfs.server.namenode.snapshot.DirectoryWithSnapshotFeature$ChildrenDiff.destroyDeletedList(DirectoryWithSnapshotFeature.java:119)
>
> org.apache.hadoop.hdfs.server.namenode.snapshot.DirectoryWithSnapshotFeature$ChildrenDiff.access$400(DirectoryWithSnapshotFeature.java:61)
>
> org.apache.hadoop.hdfs.server.namenode.snapshot.DirectoryWithSnapshotFeature$DirectoryDiff.destroyDiffAndCollectBlocks(DirectoryWithSnapshotFeature.java:319)
>
> org.apache.hadoop.hdfs.server.namenode.snapshot.DirectoryWithSnapshotFeature$DirectoryDiff.destroyDiffAndCollectBlocks(DirectoryWithSnapshotFeature.java:167)
>
> org.apache.hadoop.hdfs.server.namenode.snapshot.AbstractINodeDiffList.deleteSnapshotDiff(AbstractINodeDiffList.java:83)
>
> org.apache.hadoop.hdfs.server.namenode.snapshot.DirectoryWithSnapshotFeature.cleanDirectory(DirectoryWithSnapshotFeature.java:745)
>
> org.apache.hadoop.hdfs.server.namenode.INodeDirectory.cleanSubtree(INodeDirectory.java:776)
>
> org.apache.hadoop.hdfs.server.namenode.INodeDirectory.cleanSubtreeRecursively(INodeDirectory.java:747)
>
> org.apache.hadoop.hdfs.server.namenode.snapshot.DirectoryWithSnapshotFeature.cleanDirectory(DirectoryWithSnapshotFeature.java:747)
>
> org.apache.hadoop.hdfs.server.namenode.INodeDirectory.cleanSubtree(INodeDirectory.java:776)
>
> org.apache.hadoop.hdfs.server.namenode.INodeDirectory.cleanSubtreeRecursively(INodeDirectory.java:747)
>
> org.apache.hadoop.hdfs.server.namenode.INodeDirectory.cleanSubtree(INodeDirectory.java:789)
> {noformat}
> After the ZKFC determined NameNode was down and advanced epoch, the NN
> finished deleting snapshot, and sent the edit to journal nodes, but it was
> rejected because epoch was updated. See the following stacktrace:
> {noformat}
> 10.0.16.21:8485: IPC's epoch 17 is less than the last promised epoch 18
> at
> org.apache.hadoop.hdfs.qjournal.server.Journal.checkRequest(Journal.java:429)
> at
> org.apache.hadoop.hdfs.qjournal.server.Journal.checkWriteRequest(Journal.java:457)
> at
> org.apache.hadoop.hdfs.qjournal.server.Journal.journal(Journal.java:352)
> at
> org.apache.hadoop.hdfs.qjournal.server.JournalNodeRpcServer.journal(JournalNodeRpcServer.java:149)
> at
> org.apache.hadoop.hdfs.qjournal.protocolPB.QJournalProtocolServerSideTranslatorPB.journal(QJournalProtocolServerSideTranslatorPB.java:158)
> at
> org.apache.hadoop.hdfs.qjournal.protocol.QJournalProtocolProtos$QJournalProtocolService$2.callBlockingMethod(QJournalProtocolProtos.java:25421)
> at
> org.apache.hadoop.ipc.ProtobufRpcEngine$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)
> at
> org.apache.hadoop.hdfs.qjournal.client.QuorumException.create(QuorumException.java:81)
> at
> org.apache.hadoop.hdfs.qjournal.client.QuorumCall.rethrowException(QuorumCall.java:223)
> at
> org.apache.hadoop.hdfs.qjournal.client.AsyncLoggerSet.waitForWriteQuorum(AsyncLoggerSet.java:142)
> at
> org.apache.hadoop.hdfs.qjournal.client.QuorumOutputStream.flushAndSync(QuorumOutputStream.java:107)
> at
> org.apache.hadoop.hdfs.server.namenode.EditLogOutputStream.flush(EditLogOutputStream.java:113)
> at
> org.apache.hadoop.hdfs.server.namenode.EditLogOutputStream.flush(EditLogOutputStream.java:107)
> at
> org.apache.hadoop.hdfs.server.namenode.JournalSet$JournalSetOutputStream$8.apply(JournalSet.java:533)
> at
> org.apache.hadoop.hdfs.server.namenode.JournalSet.mapJournalsAndReportErrors(JournalSet.java:393)
> at
> org.apache.hadoop.hdfs.server.namenode.JournalSet.access$100(JournalSet.java:57)
> at
> org.apache.hadoop.hdfs.server.namenode.JournalSet$JournalSetOutputStream.flush(JournalSet.java:529)
> at
> org.apache.hadoop.hdfs.server.namenode.FSEditLog.logSync(FSEditLog.java:641)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.deleteSnapshot(FSNamesystem.java:8507)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.deleteSnapshot(NameNodeRpcServer.java:1469)
> at
> org.apache.hadoop.hdfs.server.namenode.AuthorizationProviderProxyClientProtocol.deleteSnapshot(AuthorizationProviderProxyClientProtocol.java:717)
> at
> org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.deleteSnapshot(ClientNamenodeProtocolServerSideTranslatorPB.java:1061)
> 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)
> {noformat}
> Finally NameNode shut itself down because it had too many quorum errors.
> Setting priority to critical because it resulted in NameNode crash.
> We think deleteSnapshot should be made asynchronous. It should delete the
> root of snapshot directory, and then put the rest of work into an
> asynchronous thread. Credit: [~yzhangal] for proposing this idea.
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