On Mon, May 9, 2011 at 10:53 AM, Dmitriy Lyubimov <[email protected]> wrote:
> Ok then i am missing some fundamental knowledge here about the 'job > jar'. It's probably a lame question, but i'll try to ask it anyway. > What is a "job jar"? Is it a java spec or hadoop spec? > It's not a spec at all. It's a hadoop convention. The jar you pass in to the hadoop shell script "hadoop jar mystuff.jar myclassname -myargs") has a MANIFEST which appends to the classpath of the mappers and reducers the contents of its own lib directory (inside the jar), where other jars reside. This is exactly analogous to the way servlet containers deal with .war files (except that WAR files became an actual spec). People in hadoop-land call the "jar with manifest pointing to its own internal lib directory" as a "job" jar. -jake
