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Posted to common-commits@hadoop.apache.org by Apache Wiki <wi...@apache.org> on 2007/05/01 20:42:26 UTC

[Lucene-hadoop Wiki] Update of "HowToDebugMapReducePrograms" by JackHebert

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The following page has been changed by JackHebert:
http://wiki.apache.org/lucene-hadoop/HowToDebugMapReducePrograms

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   * '''jstack''': Get the call stack for a given Java process
  These commands were first included in Sun's Java 1.5.
  
+ == Setting Task Status ==
+ 
+ The map and reduce interfaces both include a parameter 'Reporter reporter'. The method Reporter.setStatus(String status) changes the displayed status of the map task and is visable on the jobtracker web page. 
+ 
+ This can be extremely useful to display debug information about the current record being handled, or setting certain debug flags about the status of the mapper. While running locally on a small data set can find many bugs, large data sets may contain pathological cases that are otherwise unexepcted. This method of debugging can help catch those cases.
+