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Posted to common-issues@hadoop.apache.org by "Tarjei Huse (Updated) (JIRA)" <ji...@apache.org> on 2012/02/09 08:21:00 UTC
[jira] [Updated] (HADOOP-8045)
org.apache.hadoop.mapreduce.lib.output.MultipleOutputs does not handle many
files well
[ https://issues.apache.org/jira/browse/HADOOP-8045?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Tarjei Huse updated HADOOP-8045:
--------------------------------
Status: Patch Available (was: Open)
This patch changes the MultipleOutputs API to provide a way to close files while running the reducer.
> 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
> 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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