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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. +
