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https://issues.apache.org/jira/browse/HDFS-13120?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16357594#comment-16357594
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Xiaoyu Yao commented on HDFS-13120:
-----------------------------------
Thanks [~kihwal] for reporting the break. I will make the adjustment for the
unit test like I did for branch-2.7.
> Snapshot diff could be corrupted after concat
> ---------------------------------------------
>
> Key: HDFS-13120
> URL: https://issues.apache.org/jira/browse/HDFS-13120
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode, snapshots
> Affects Versions: 2.7.0
> Reporter: Xiaoyu Yao
> Assignee: Xiaoyu Yao
> Priority: Major
> Fix For: 3.1.0, 2.10.0, 2.9.1, 3.0.1, 2.8.4, 2.7.6
>
> Attachments: HDFS-13120.001.patch, HDFS-13120.002.patch
>
>
> The snapshot diff can be corrupted after concat files. This could lead to
> Assertion upon DeleteSnapshot and getSnapshotDiff operations later.
> For example, we have seen customers hit stack trace similar to the one below
> but during loading edit entry of DeleteSnapshotOp. After the investigation,
> we found this is a regression caused by HDFS-3689 where the snapshot diff is
> not fully cleaned up after concat.
> I will post the unit test to repro this and fix for it shortly.
> {code}
> org.apache.hadoop.ipc.RemoteException(java.lang.AssertionError): Element
> already exists: element=0.txt, CREATED=[0.txt, 1.txt, 2.txt]
> at org.apache.hadoop.hdfs.util.Diff.insert(Diff.java:196)
> at org.apache.hadoop.hdfs.util.Diff.create(Diff.java:216)
> at org.apache.hadoop.hdfs.util.Diff.combinePosterior(Diff.java:463)
> at
> org.apache.hadoop.hdfs.server.namenode.snapshot.DirectoryWithSnapshotFeature$DirectoryDiff.combinePosteriorAndCollectBlocks(DirectoryWithSnapshotFeature.java:205)
> at
> org.apache.hadoop.hdfs.server.namenode.snapshot.DirectoryWithSnapshotFeature$DirectoryDiff.combinePosteriorAndCollectBlocks(DirectoryWithSnapshotFeature.java:162)
> at
> org.apache.hadoop.hdfs.server.namenode.snapshot.AbstractINodeDiffList.deleteSnapshotDiff(AbstractINodeDiffList.java:100)
> at
> org.apache.hadoop.hdfs.server.namenode.snapshot.DirectoryWithSnapshotFeature.cleanDirectory(DirectoryWithSnapshotFeature.java:728)
> at
> org.apache.hadoop.hdfs.server.namenode.INodeDirectory.cleanSubtree(INodeDirectory.java:830)
> at
> org.apache.hadoop.hdfs.server.namenode.snapshot.DirectorySnapshottableFeature.removeSnapshot(DirectorySnapshottableFeature.java:237)
> at
> org.apache.hadoop.hdfs.server.namenode.INodeDirectory.removeSnapshot(INodeDirectory.java:292)
> at
> org.apache.hadoop.hdfs.server.namenode.snapshot.SnapshotManager.deleteSnapshot(SnapshotManager.java:321)
> at
> org.apache.hadoop.hdfs.server.namenode.FSDirSnapshotOp.deleteSnapshot(FSDirSnapshotOp.java:249)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.deleteSnapshot(FSNamesystem.java:6566)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.deleteSnapshot(NameNodeRpcServer.java:1823)
> at
> org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.deleteSnapshot(ClientNamenodeProtocolServerSideTranslatorPB.java:1200)
> at
> org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
> at
> org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:524)
> at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:1007)
> at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:873)
> at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:819)
> 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:1965)
> at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2679)
> {code}
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