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From "Mark Desnoyer (JIRA)" <j...@apache.org>
Subject [jira] Created: (MAPREDUCE-821) JobClient.runJob leaks file descriptors
Date Mon, 03 Aug 2009 15:43:15 GMT
JobClient.runJob leaks file descriptors
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                 Key: MAPREDUCE-821
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-821
             Project: Hadoop Map/Reduce
          Issue Type: Bug
         Environment: Driver running on Ubuntu Jaunty x86, cluster running a Linux variant.

            Reporter: Mark Desnoyer
            Priority: Critical


In a Java-based driver that runs multiple MapReduce jobs (e.g. Mahout's K-means implementation),
numerous calls to JobClient.runJob will cause many RPC connections to be opened and then never
closed. This results in the driver job leaking file descriptors and will eventually crash
once the OS limit is reached for Too Many Open Files.

This has been verified in Hadoop 18.3 by running the driver and as new MapReduce jobs are
run, lsof -p dhows an increasing number of open TCP connections to the cluster.

Looking at the current code in the trunk, it looks like this is caused by runJob not calling
close() on the JobClient object it creates. Or alternatively, it's cause by the fact that
JobClient does not have a destructor that calls close().

I am going to verify this hypothesis and post a patch.

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