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Posted to common-commits@hadoop.apache.org by Apache Wiki <wi...@apache.org> on 2014/03/20 09:46:48 UTC
[Hadoop Wiki] Trivial Update of "FAQ" by LewisJohnMcgibbney
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The "FAQ" page has been changed by LewisJohnMcgibbney:
https://wiki.apache.org/hadoop/FAQ?action=diff&rev1=109&rev2=110
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== How do I change final output file name with the desired name rather than in partitions like part-00000, part-00001? ==
- You can subclass the [[http://svn.apache.org/viewvc/hadoop/core/trunk/src/mapred/org/apache/hadoop/mapred/OutputFormat.java?view=markup|OutputFormat.java]] class and write your own. You can look at the code of [[http://svn.apache.org/viewvc/hadoop/core/trunk/src/mapred/org/apache/hadoop/mapred/TextOutputFormat.java?view=markup|TextOutputFormat]] [[http://svn.apache.org/viewvc/hadoop/core/trunk/src/mapred/org/apache/hadoop/mapred/MultipleOutputFormat.java?view=markup|MultipleOutputFormat.java]] etc. for reference. It might be the case that you only need to do minor changes to any of the existing Output Format classes. To do that you can just subclass that class and override the methods you need to change.
+ You can subclass the [[http://hadoop.apache.org/docs/current/api/index.html?org/apache/hadoop/mapred/OutputFormat.html|OutputFormat.java]] class and write your own. You can locate and browse the code of [[http://hadoop.apache.org/docs/current/api/index.html?org/apache/hadoop/mapred/TextOutputFormat.html|TextOutputFormat]] [[http://hadoop.apache.org/docs/current/api/index.html?org/apache/hadoop/mapred/lib/MultipleOutputFormat.html]] etc. for reference. It might be the case that you only need to do minor changes to any of the existing Output Format classes. To do that you can just subclass that class and override the methods you need to change.
== When writing a New InputFormat, what is the format for the array of string returned by InputSplit\#getLocations()? ==
It appears that DatanodeID.getHost() is the standard place to retrieve this name, and the machineName variable, populated in DataNode.java\#startDataNode, is where the name is first set. The first method attempted is to get "slave.host.name" from the configuration; if that is not available, DNS.getDefaultHost is used instead.