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https://issues.apache.org/jira/browse/HADOOP-927?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Doug Cutting resolved HADOOP-927.
---------------------------------
Resolution: Duplicate
> MapReduce is Broken for User-Defined Classes
> --------------------------------------------
>
> Key: HADOOP-927
> URL: https://issues.apache.org/jira/browse/HADOOP-927
> Project: Hadoop
> Issue Type: Bug
> Components: mapred
> Affects Versions: 0.11.0
> Reporter: Albert Chern
> Priority: Critical
>
> Checked out trunk today and all of my jobs with a user-defined class as a map
> output value class fail with a ClassNotFoundException. Here's the stack
> trace:
> java.lang.RuntimeException: java.lang.RuntimeException:
> java.lang.ClassNotFoundException: test.StringWrapper
> at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:344)
> at
> org.apache.hadoop.mapred.JobConf.getMapOutputValueClass(JobConf.java:406)
> at org.apache.hadoop.mapred.ReduceTaskRunner.(ReduceTaskRunner.java:339)
> at org.apache.hadoop.mapred.ReduceTask.createRunner(ReduceTask.java:91)
> at
> org.apache.hadoop.mapred.TaskTracker$TaskInProgress.launchTask(TaskTracker.java:983)
> at
> org.apache.hadoop.mapred.TaskTracker.launchTaskForJob(TaskTracker.java:366)
> at
> org.apache.hadoop.mapred.TaskTracker.localizeJob(TaskTracker.java:359)
> at
> org.apache.hadoop.mapred.TaskTracker.startNewTask(TaskTracker.java:823)
> at
> org.apache.hadoop.mapred.TaskTracker.offerService(TaskTracker.java:510)
> at org.apache.hadoop.mapred.TaskTracker.run(TaskTracker.java:852)
> at org.apache.hadoop.mapred.TaskTracker.main(TaskTracker.java:1494)
> I haven't looked deeply into it, but I would guess that the problem is in the
> constructor of ReduceTaskRunner where it attempts to create a
> SequenceFile.Sorter for the map output value class. It's probably done in
> the main TaskTracker JVM process, so external libraries are not on its
> classpath.
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