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From Kumar Ravi <kum...@us.ibm.com>
Subject Hadoop-8192 and rackToBlocks ordering
Date Wed, 21 Mar 2012 20:47:47 GMT


 We have been looking at IBM JDK junit failures on Hadoop-1.0.1
independently and have ran into the same failures as reported in this JIRA.
I have a question based upon what I have observed below.

We started debugging the problems in the testcase -
The testcase fails because the number of splits returned back from
CombineFileInputFormat.getSplits() is 1 when using IBM JDK whereas the
expected return value is 2.

So far, we have found the reason for this difference in number of splits is
because the order in which elements in the nodeToBlocks hashmap get created
is in the reverse order that Sun JDK creates.

The question I have at this point is -- Should there be a strict dependency
in the order in which the rackToBlocks hashmap gets populated, to determine
the number of splits that get should get created in a hadoop cluster? Is
this Working as designed?


Kumar Ravi
IBM Linux Technology Center
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