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From Apache Wiki <wikidi...@apache.org>
Subject [Lucene-hadoop Wiki] Update of "HowToDebugMapReducePrograms" by JackHebert
Date Tue, 01 May 2007 18:42:26 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Lucene-hadoop Wiki" for change notification.

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

------------------------------------------------------------------------------
   * '''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.
+ 

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