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From "Tarjei Huse (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HADOOP-8045) org.apache.hadoop.mapreduce.lib.output.MultipleOutputs does not handle many files well
Date Thu, 09 Feb 2012 07:18:59 GMT
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: 1.0.0, 0.21.0
         Environment: Cloudera CH3 release.
            Reporter: Tarjei Huse


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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