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From Kay Ousterhout <...@eecs.berkeley.edu>
Subject 5 second minimum shuffle time
Date Wed, 29 May 2013 03:00:29 GMT

I'm running v0.23 in a large cluster, and have found that the shuffle time
for reduce tasks is always at least 5 seconds, even when the amount of data
read by the reduce task is tiny (e.g., just 18 bytes).  This shuffle time
floor suggests that there's a heartbeat interval or something that has to
elapse before the shuffle begins, but I can't find any sign of such a delay
in the code base.  Can anyone shed some light on why this is occurring?


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