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From "Harsh J (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-8045) org.apache.hadoop.mapreduce.lib.output.MultipleOutputs does not handle many files well
Date Thu, 09 Feb 2012 08:39:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-8045?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13204360#comment-13204360
] 

Harsh J commented on HADOOP-8045:
---------------------------------

Tarjei,

Perhaps you may want to increase the xceiver limits on your DN to allow more writes?
                
> org.apache.hadoop.mapreduce.lib.output.MultipleOutputs does not handle many files well
> --------------------------------------------------------------------------------------
>
>                 Key: HADOOP-8045
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8045
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: io
>    Affects Versions: 0.21.0, 1.0.0
>         Environment: Cloudera CH3 release.
>            Reporter: Tarjei Huse
>              Labels: patch
>         Attachments: hadoop-multiple-outputs.patch
>
>
> We were tryong to use MultipleOutputs to write one file per key. This produced the error:
> exception:
> org.apache.hadoop.ipc.RemoteException: java.io.IOException: File
> /user/me/part6/_temporary/
> _attempt_201202071305_0017_r_000000_2/2011-11-18-22-
> attempt_201202071305_0017_r_000000_2-r-00000
> could only be replicated to 0 nodes, instead of 1
>     at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:
> 1520)
>     at
> org.apache.hadoop.hdfs.server.namenode.NameNode.addBlock(NameNode.java:
> 665)
>     at sun.reflect.GeneratedMethodAccessor4.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:
> 1157) 
> When the nr. of files processed increased over 20 on a single developer system. 
> The solution proved to be to close each RecordWriter when the reducer was finished with
a key, something that required that we extended the multiple outputs to fetch the recordwriter
- not a good solution. 

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