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https://issues.apache.org/jira/browse/HDFS-9249?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14960660#comment-14960660
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Wei-Chiu Chuang commented on HDFS-9249:
---------------------------------------

Hi [~steve_l],
thanks for the long and detailed guideline :) I am relatively new to the Hadoop 
world so I did not get it right the first time.

I am now able to trigger the NPE by setting 
    c.set("hadoop.security.authentication", "kerberos");
    c.set("dfs.namenode.keytab.file", "");
for the backup node, while the primary name node is still configured in simple 
auth mode.

If I apply the patch, it will then throw IOException "Running in secure mode, 
but config doesn't have a key tab" instead of NPE.

Now, this does not imply this is what caused the NPE in the original jenkins 
job, but it does show the patch can shutdown relatively gracefully.

> NPE thrown if an IOException is thrown in NameNode.<init>
> ---------------------------------------------------------
>
>                 Key: HDFS-9249
>                 URL: https://issues.apache.org/jira/browse/HDFS-9249
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 2.7.1
>            Reporter: Wei-Chiu Chuang
>            Assignee: Wei-Chiu Chuang
>            Priority: Minor
>              Labels: supportability
>         Attachments: HDFS-9249.001.patch
>
>
> This issue was found when running test case 
> TestBackupNode.testCheckpointNode, but upon closer look, the problem is not 
> due to the test case.
> Looks like an IOException was thrown in
>     try {
>       initializeGenericKeys(conf, nsId, namenodeId);
>       initialize(conf);
>       try {
>         haContext.writeLock();
>         state.prepareToEnterState(haContext);
>         state.enterState(haContext);
>       } finally {
>         haContext.writeUnlock();
>       }
> causing the namenode to stop, but the namesystem was not yet properly 
> instantiated, causing NPE.
> I tried to reproduce locally, but to no avail.
> Because I could not reproduce the bug, and the log does not indicate what 
> caused the IOException, I suggest make this a supportability JIRA to log the 
> exception for future improvement.
> Stacktrace
> java.lang.NullPointerException: null
> at 
> org.apache.hadoop.hdfs.server.namenode.NameNode.getFSImage(NameNode.java:906)
> at org.apache.hadoop.hdfs.server.namenode.BackupNode.stop(BackupNode.java:210)
> at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:827)
> at 
> org.apache.hadoop.hdfs.server.namenode.BackupNode.<init>(BackupNode.java:89)
> at 
> org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1474)
> at 
> org.apache.hadoop.hdfs.server.namenode.TestBackupNode.startBackupNode(TestBackupNode.java:102)
> at 
> org.apache.hadoop.hdfs.server.namenode.TestBackupNode.testCheckpoint(TestBackupNode.java:298)
> at 
> org.apache.hadoop.hdfs.server.namenode.TestBackupNode.testCheckpointNode(TestBackupNode.java:130)
> The last few lines of log:
> 2015-10-14 19:45:07,807 INFO namenode.NameNode 
> (NameNode.java:createNameNode(1422)) - createNameNode [-checkpoint]
> 2015-10-14 19:45:07,807 INFO impl.MetricsSystemImpl 
> (MetricsSystemImpl.java:init(158)) - CheckpointNode metrics system started 
> (again)
> 2015-10-14 19:45:07,808 INFO namenode.NameNode 
> (NameNode.java:setClientNamenodeAddress(402)) - fs.defaultFS is 
> hdfs://localhost:37835
> 2015-10-14 19:45:07,808 INFO namenode.NameNode 
> (NameNode.java:setClientNamenodeAddress(422)) - Clients are to use 
> localhost:37835 to access this namenode/service.
> 2015-10-14 19:45:07,810 INFO hdfs.MiniDFSCluster 
> (MiniDFSCluster.java:shutdown(1708)) - Shutting down the Mini HDFS Cluster
> 2015-10-14 19:45:07,810 INFO namenode.FSNamesystem 
> (FSNamesystem.java:stopActiveServices(1298)) - Stopping services started for 
> active state
> 2015-10-14 19:45:07,811 INFO namenode.FSEditLog 
> (FSEditLog.java:endCurrentLogSegment(1228)) - Ending log segment 1
> 2015-10-14 19:45:07,811 INFO namenode.FSNamesystem 
> (FSNamesystem.java:run(5306)) - NameNodeEditLogRoller was interrupted, exiting
> 2015-10-14 19:45:07,811 INFO namenode.FSEditLog 
> (FSEditLog.java:printStatistics(703)) - Number of transactions: 3 Total time 
> for transactions(ms): 0 Number of transactions batched in Syncs: 0 Number of 
> syncs: 4 SyncTimes(ms): 2 1 
> 2015-10-14 19:45:07,811 INFO namenode.FSNamesystem 
> (FSNamesystem.java:run(5373)) - LazyPersistFileScrubber was interrupted, 
> exiting
> 2015-10-14 19:45:07,822 INFO namenode.FileJournalManager 
> (FileJournalManager.java:finalizeLogSegment(142)) - Finalizing edits file 
> /data/jenkins/workspace/CDH5.5.0-Hadoop-HDFS-2.6.0/hadoop-hdfs-project/hadoop-hdfs/target/test/data/dfs/name1/current/edits_inprogress_0000000000000000001
>  -> 
> /data/jenkins/workspace/CDH5.5.0-Hadoop-HDFS-2.6.0/hadoop-hdfs-project/hadoop-hdfs/target/test/data/dfs/name1/current/edits_0000000000000000001-0000000000000000003
> 2015-10-14 19:45:07,835 INFO namenode.FileJournalManager 
> (FileJournalManager.java:finalizeLogSegment(142)) - Finalizing edits file 
> /data/jenkins/workspace/CDH5.5.0-Hadoop-HDFS-2.6.0/hadoop-hdfs-project/hadoop-hdfs/target/test/data/dfs/name2/current/edits_inprogress_0000000000000000001
>  -> 
> /data/jenkins/workspace/CDH5.5.0-Hadoop-HDFS-2.6.0/hadoop-hdfs-project/hadoop-hdfs/target/test/data/dfs/name2/current/edits_0000000000000000001-0000000000000000003
> 2015-10-14 19:45:07,836 INFO blockmanagement.CacheReplicationMonitor 
> (CacheReplicationMonitor.java:run(169)) - Shutting down 
> CacheReplicationMonitor
> 2015-10-14 19:45:07,836 INFO ipc.Server (Server.java:stop(2485)) - Stopping 
> server on 37835
> 2015-10-14 19:45:07,837 INFO ipc.Server (Server.java:run(718)) - Stopping IPC 
> Server listener on 37835
> 2015-10-14 19:45:07,837 INFO ipc.Server (Server.java:run(844)) - Stopping IPC 
> Server Responder
> 2015-10-14 19:45:07,837 INFO blockmanagement.BlockManager 
> (BlockManager.java:run(3781)) - Stopping ReplicationMonitor.
> 2015-10-14 19:45:07,838 WARN blockmanagement.DecommissionManager 
> (DecommissionManager.java:run(78)) - Monitor interrupted: 
> java.lang.InterruptedException: sleep interrupted
> 2015-10-14 19:45:07,844 INFO namenode.FSNamesystem 
> (FSNamesystem.java:stopActiveServices(1298)) - Stopping services started for 
> active state
> 2015-10-14 19:45:07,845 INFO namenode.FSNamesystem 
> (FSNamesystem.java:stopStandbyServices(1386)) - Stopping services started for 
> standby state
> 2015-10-14 19:45:07,848 INFO mortbay.log (Slf4jLog.java:info(67)) - Stopped 
> HttpServer2$SelectChannelConnectorWithSafeStartup@localhost:0



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