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https://issues.apache.org/jira/browse/HADOOP-8192?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13236990#comment-13236990
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Kumar Ravi commented on HADOOP-8192:
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While debugging this issue it was observed that the order by which the
racksToBlocks HashMap gets populated seems to matter. As per Robert Evans and
Devaraj Das, it appears by design that the order should not matter.
The reason order happens to play a role here is that as soon as all the blocks
are accounted for, getMoreSplits() stops iterating through the racks, and
depending upon which rack(s) each block is replicated on, and depending upon
when each rack is processed in the loop within getMoreSplits(), one can end up
with different split counts, and as a result fail the testcase in some
situations.
Specifically for this testcase, there are 3 racks that are simulated where each
of these 3 racks have a datanode each. Datanode 1 has replicas of all the
blocks of all the 3 files (file1, file2, and file3) while Datanode 2 has all
the blocks of files file2 and file 3 and Datanode 3 has all the blocks of only
file3. As soon as Rack 1 is processed, getMoreSplits() exits with a split count
of the number of times it stays in this loop. So in this scenario, if Rack1
gets processed last, one will end up with a split count of 3. If Rack1 gets
processed in the beginning, split count will be 1. The testcase is expecting a
return value of 3 which is the value returned if running on Sun JVM, but a
value of 1 or 2 may be returned depending on when rack1 gets processed.
> Fix unit test failures with IBM's JDK
> -------------------------------------
>
> Key: HADOOP-8192
> URL: https://issues.apache.org/jira/browse/HADOOP-8192
> Project: Hadoop Common
> Issue Type: Bug
> Environment: java version "1.6.0"
> Java(TM) SE Runtime Environment (build pxi3260sr10-20111208_01(SR10))
> IBM J9 VM (build 2.4, JRE 1.6.0 IBM J9 2.4 Linux x86-32
> jvmxi3260sr10-20111207_96808 (JIT enabled, AOT enabled)
> J9VM - 20111207_096808
> JIT - r9_20111107_21307ifx1
> GC - 20110519_AA)
> JCL - 20111104_02
> Reporter: Devaraj Das
>
> Some tests fail with IBM's JDK. They are
> org.apache.hadoop.mapred.lib.TestCombineFileInputFormat,
> org.apache.hadoop.mapreduce.lib.input.TestCombineFileInputFormat,
> org.apache.hadoop.streaming.TestStreamingBadRecords,
> org.apache.hadoop.mapred.TestCapacityScheduler. This jira is to track fixing
> these.
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