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https://issues.apache.org/jira/browse/HDFS-9249?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14986491#comment-14986491
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Wei-Chiu Chuang commented on HDFS-9249:
---------------------------------------
(1) It is not intuitive initially because of the throw-catch control flow. When
BackupNode is being instantiated, NameNode.NameNode() calls
BackupNode.initialize().
BackupNode.initialize() also instantiates namesystem object, but if an
IOException is thrown before namesystem is instantiated, the controls goes to
the catch block in NameNode.initialize(), which in turn calls NameNode.stop().
NameNode.stop() then attempts to call an method of namesystem object despite
namesystem object is not instantiated.
(2) I am not sure why this is happening. I tested the test case on both Mac and
Linux and both turned out fine. The Hadoop QA also did not see the unexpected
exception thrown.
Thanks
> 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, HDFS-9249.002.patch,
> HDFS-9249.003.patch, HDFS-9249.004.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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