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HDFS, mail # dev - Probably a bug in FsEditLog


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Re: Probably a bug in FsEditLog
Harsh J 2013-04-08, 09:24
Anty,

Worth checking if you can spot the bug in branch-1 as well:
http://svn.apache.org/repos/asf/hadoop/common/branches/branch-1/src/hdfs/org/apache/hadoop/hdfs/server/namenode/FSEditLog.java
(and other refs under
http://svn.apache.org/repos/asf/hadoop/common/branches/branch-1/src/hdfs/org/apache/hadoop/hdfs/server/namenode/)

On Mon, Apr 8, 2013 at 2:44 PM, Anty <[EMAIL PROTECTED]> wrote:
> @Harsh
> I'm using CDH3u4.However, the processing logical with regard to FSEditlog
> between CDH3U4 and hadoop 1.0.2 is almost the same.
> So i'm not sure it is proper to file a JIRA?
>
> On Mon, Apr 8, 2013 at 4:33 PM, Harsh J <[EMAIL PROTECTED]> wrote:
>
>> Thanks for analyzing and reporting this Anty,
>>
>> What version of Apache Hadoop 1.x are you encountering this on? If
>> you've spotted the code issue on branch-1, please do log a HDFS JIRA
>> with some NN logs and your other details.
>>
>> On Sun, Apr 7, 2013 at 3:18 PM, Anty <[EMAIL PROTECTED]> wrote:
>> > Hi:ALL
>> >
>> > In our cluster, we configure the NameNode to write to both local  and NFS
>> > mounted directories. When the NFS mounted directory is inaccessible, the
>> > NameNode should keep running without error, but our namenode crash with
>> > following stack trace.
>> >
>> > 2013-04-02 23:35:21,535 WARN
>> org.apache.hadoop.hdfs.server.common.Storage:
>> >> Removing storage dir /nfs2-mount/onest3/dfs/name
>> >> 2013-04-02 23:35:21,536 FATAL
>> >> org.apache.hadoop.hdfs.server.namenode.FSNamesystem: Unable to find
>> edits
>> >> stream with IO error
>> >> java.lang.Exception: Unable to find edits stream with IO error
>> >>         at
>> >>
>> org.apache.hadoop.hdfs.server.namenode.FSEditLog.fatalExit(FSEditLog.java:430)
>> >>         at
>> >>
>> org.apache.hadoop.hdfs.server.namenode.FSEditLog.removeEditsStreamsAndStorageDirs(FSEditLog.java:519)
>> >>         at
>> >>
>> org.apache.hadoop.hdfs.server.namenode.FSEditLog.logSync(FSEditLog.java:1139)
>> >>         at
>> >>
>> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.completeFile(FSNamesystem.java:1641)
>> >>         at
>> >>
>> org.apache.hadoop.hdfs.server.namenode.NameNode.complete(NameNode.java:689)
>> >>         at sun.reflect.GeneratedMethodAccessor21.invoke(Unknown Source)
>> >>         at
>> >>
>> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
>> >>         at java.lang.reflect.Method.invoke(Method.java:597)
>> >>         at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:557)
>> >>         at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1434)
>> >>         at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1430)
>> >>         at java.security.AccessController.doPrivileged(Native Method)
>> >>         at javax.security.auth.Subject.doAs(Subject.java:396)
>> >>         at
>> >>
>> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1177)
>> >>         at org.apache.hadoop.ipc.Server$Handler.run(Server.java:1428)
>> >> 2013-04-02 23:35:21,539 INFO
>> >> org.apache.hadoop.hdfs.server.namenode.NameNode: SHUTDOWN_MSG:
>> >>
>> >
>> > According to the stack trace, When NameNode tries to sync edit log, it
>> does
>> > identify the mounted NFS directory is inaccessible, and attempt to remove
>> > it from the FSEditLog#editStreams. However, it found the edit stream
>> > corresponding to the mounted NFS has already been removed. Under this
>> > circumstance, NameNode just kill itself, aborted!
>> >
>> >  After looking through the source code of HDFS, I found there is another
>> > code path of removing edit stream from FSEditLog#editStreams, which can
>> > cause above race condition. In method FSEditLog#logEdit
>> >
>> >
>> >>    if (getNumEditStreams() < 1)
>> >>         {
>> >>             throw new AssertionError("No edit streams to log to");
>> >>         }
>> >>         long start = FSNamesystem.now();
>> >>         for (int idx = 0; idx < editStreams.size(); idx++)
>> >>         {
>> >>             EditLogOutputStream eStream = editStreams.get(idx);

Harsh J