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From "Wei-Chiu Chuang (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-10729) NameNode crashes when loading edits because max directory items is exceeded
Date Mon, 08 Aug 2016 02:36:20 GMT
Wei-Chiu Chuang created HDFS-10729:
--------------------------------------

             Summary: NameNode crashes when loading edits because max directory items is exceeded
                 Key: HDFS-10729
                 URL: https://issues.apache.org/jira/browse/HDFS-10729
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: namenode
    Affects Versions: 2.7.2
            Reporter: Wei-Chiu Chuang
            Assignee: Wei-Chiu Chuang
            Priority: Critical


We encountered a bug where Standby NameNode crashes due to an NPE when loading edits.

{noformat}
2016-08-05 15:06:00,983 ERROR org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader: Encountered
exception on operation AddOp [length=0, inodeId=789272719, path=[path], replication=3, mtime=1470379597935,
atime=1470379597935, blockSize=134217728, blocks=[], permissions=bdi:supergroup:rw-r--r--,
aclEntries=null, clientName=DFSClient_NONMAPREDUCE_1495395702_1, clientMachine=10.210.119.136,
overwrite=true, RpcClientId=a1512eeb-65e4-43dc-8aa8-d7a1af37ed30, RpcCallId=417, storagePolicyId=0,
opCode=OP_ADD, txid=4212503758]
java.lang.NullPointerException
        at org.apache.hadoop.hdfs.server.namenode.FSDirectory.getFileEncryptionInfo(FSDirectory.java:2914)
        at org.apache.hadoop.hdfs.server.namenode.FSDirectory.createFileStatus(FSDirectory.java:2469)
        at org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.applyEditLogOp(FSEditLogLoader.java:375)
        at org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.loadEditRecords(FSEditLogLoader.java:230)
        at org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.loadFSEdits(FSEditLogLoader.java:139)
        at org.apache.hadoop.hdfs.server.namenode.FSImage.loadEdits(FSImage.java:829)
        at org.apache.hadoop.hdfs.server.namenode.FSImage.loadEdits(FSImage.java:810)
        at org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer.doTailEdits(EditLogTailer.java:232)
        at org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer$EditLogTailerThread.doWork(EditLogTailer.java:331)
        at org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer$EditLogTailerThread.access$200(EditLogTailer.java:284)
        at org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer$EditLogTailerThread$1.run(EditLogTailer.java:301)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:360)
        at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1651)
        at org.apache.hadoop.security.SecurityUtil.doAsLoginUserOrFatal(SecurityUtil.java:410)
        at org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer$EditLogTailerThread.run(EditLogTailer.java:297)
{noformat}

The NameNode crashes and can not be restarted. After some research, we turned on debug log
of org.apache.hadoop.hdfs.StateChange, restart the NN, and we saw the following exception
which induced NPE:

{noformat}
16/08/07 18:51:15 DEBUG hdfs.StateChange: DIR* FSDirectory.unprotectedAddFile: exception when
add [path] to the file system
org.apache.hadoop.hdfs.protocol.FSLimitException$MaxDirectoryItemsExceededException: The directory
item limit of [path] is exceeded: limit=1048576 items=1049332
        at org.apache.hadoop.hdfs.server.namenode.FSDirectory.verifyMaxDirItems(FSDirectory.java:2060)
        at org.apache.hadoop.hdfs.server.namenode.FSDirectory.addChild(FSDirectory.java:2112)
        at org.apache.hadoop.hdfs.server.namenode.FSDirectory.addLastINode(FSDirectory.java:2081)
        at org.apache.hadoop.hdfs.server.namenode.FSDirectory.addINode(FSDirectory.java:1900)
        at org.apache.hadoop.hdfs.server.namenode.FSDirectory.unprotectedAddFile(FSDirectory.java:368)
        at org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.applyEditLogOp(FSEditLogLoader.java:365)
        at org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.loadEditRecords(FSEditLogLoader.java:230)
        at org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.loadFSEdits(FSEditLogLoader.java:139)
        at org.apache.hadoop.hdfs.server.namenode.FSImage.loadEdits(FSImage.java:829)
        at org.apache.hadoop.hdfs.server.namenode.FSImage.loadEdits(FSImage.java:810)
        at org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer.doTailEdits(EditLogTailer.java:232)
        at org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer$1.run(EditLogTailer.java:188)
        at org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer$1.run(EditLogTailer.java:182)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:415)
        at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1671)
        at org.apache.hadoop.security.SecurityUtil.doAsUser(SecurityUtil.java:445)
        at org.apache.hadoop.security.SecurityUtil.doAsLoginUser(SecurityUtil.java:426)
        at org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer.catchupDuringFailover(EditLogTailer.java:182)
        at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startActiveServices(FSNamesystem.java:1205)
        at org.apache.hadoop.hdfs.server.namenode.NameNode$NameNodeHAContext.startActiveServices(NameNode.java:1762)
        at org.apache.hadoop.hdfs.server.namenode.ha.ActiveState.enterState(ActiveState.java:61)
        at org.apache.hadoop.hdfs.server.namenode.ha.HAState.setStateInternal(HAState.java:64)
        at org.apache.hadoop.hdfs.server.namenode.ha.StandbyState.setState(StandbyState.java:49)
        at org.apache.hadoop.hdfs.server.namenode.NameNode.transitionToActive(NameNode.java:1635)
        at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.transitionToActive(NameNodeRpcServer.java:1351)
        at org.apache.hadoop.ha.protocolPB.HAServiceProtocolServerSideTranslatorPB.transitionToActive(HAServiceProtocolServerSideTranslatorPB.java:107)
        at org.apache.hadoop.ha.proto.HAServiceProtocolProtos$HAServiceProtocolService$2.callBlockingMethod(HAServiceProtocolProtos.java:4460)
        at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:617)
        at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:1060)
        at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2086)
        at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2082)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:415)
        at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1671)
        at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2080)
{noformat}

The exception is thrown, caught and logged at debug level in {{FSDirectory#unprotectedAddFile}}.
Afterwards, a null is returned, which is used and subsequently caused NPE. HDFS-7567 reported
a similar bug, but it was deemed the NPE could only be thrown if edit is corrupt. However,
here we see an example where NPE could be thrown without corrupt edits.

Looks like the maximum number of items per directory is exceeded. This is similar to HDFS-6102
and HDFS-7482, but this happens at loading edits, rather than loading fsimage. 

A possible workaround is to increas the value of {{dfs.namenode.fs-limits.max-directory-items}}
to 6400000. But I am not sure if it would cause any side effects.



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