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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-5510) logSync() may block NameNode forever.
Date Wed, 25 Mar 2009 17:52:57 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5510?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12689177#action_12689177
] 

Tsz Wo (Nicholas), SZE commented on HADOOP-5510:
------------------------------------------------

Got a NPE in EditLogBackupOutputStream.flushAndSync(..):
{noformat}
2009-03-24 17:56:09,750 INFO  ipc.Server (Server.java:run(968)) - IPC Server handler 6 on
1441, call startCheckpoint(
NamenodeRegistration(xx.xx.xx.xx:50100, role=Backup Node)) from 127.0.0.1:1485: error: java.io.IOException:
java.lang.NullPointerException
java.io.IOException: java.lang.NullPointerException
	at org.apache.hadoop.hdfs.server.namenode.EditLogBackupOutputStream.flushAndSync(EditLogBackupOutputStream.java:163)
	at org.apache.hadoop.hdfs.server.namenode.EditLogOutputStream.flush(EditLogOutputStream.java:83)
	at org.apache.hadoop.hdfs.server.namenode.FSEditLog.logSync(FSEditLog.java:989)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startCheckpoint(FSNamesystem.java:4395)
	at org.apache.hadoop.hdfs.server.namenode.NameNode.startCheckpoint(NameNode.java:440)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:508)
	at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:959)
	at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:955)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:396)
	at org.apache.hadoop.ipc.Server$Handler.run(Server.java:953)
{noformat}

> logSync() may block NameNode forever.
> -------------------------------------
>
>                 Key: HADOOP-5510
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5510
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.14.0
>            Reporter: Konstantin Shvachko
>
> # {{FSEditLog.logSync()}} first waits until {{isSyncRunning}} is false and then performs
syncing to file streams by calling {{EditLogOutputStream.flush()}}.
> If an exception is thrown after {{isSyncRunning}} is set to {{true}} all threads will
always wait on this condition.
> An {{IOException}} may be thrown by {{EditLogOutputStream.setReadyToFlush()}} or a {{RuntimeException}}
may be thrown by {{EditLogOutputStream.flush()}} or by {{processIOError()}}.
> # The loop that calls {{eStream.flush()}} for multiple {{EditLogOutputStream}}-s is not
synchronized, which means that another thread may encounter an error and modify {{editStreams}}
by say calling {{processIOError()}}. Then the iterating process in {{logSync()}} will break
with {{IndexOutOfBoundException}}.

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