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Posted to mapreduce-issues@hadoop.apache.org by "Eric Payne (Updated) (JIRA)" <ji...@apache.org> on 2011/12/14 19:29:30 UTC
[jira] [Updated] (MAPREDUCE-3404) Speculative Execution:
speculative map tasks launched even if -Dmapreduce.map.speculative=false
[ https://issues.apache.org/jira/browse/MAPREDUCE-3404?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Eric Payne updated MAPREDUCE-3404:
----------------------------------
Attachment: MAPREDUCE-3404.1.txt
> Speculative Execution: speculative map tasks launched even if -Dmapreduce.map.speculative=false
> -----------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-3404
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-3404
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: job submission, mrv2
> Affects Versions: 0.23.0
> Environment: Hadoop version is: Hadoop 0.23.0.1110031628
> 10 node test cluster
> Reporter: patrick white
> Assignee: Eric Payne
> Priority: Critical
> Attachments: MAPREDUCE-3404.1.txt
>
>
> When forcing a mapper to take significantly longer than other map tasks, speculative map tasks are
> launched even if the mapreduce.job.maps.speculative.execution parameter is set to 'false'.
> Testcase: ran default WordCount job with spec execution set to false for both map and reduce but still saw a fifth mapper
> task launch, ran job as follows:
> hadoop --config <config> jar /tmp/testphw/wordcount.jar WordCount
> -Dmapreduce.job.maps.speculative.execution=false -Dmapreduce.job.reduces.speculative.execution=false
> /tmp/test_file_of_words* /tmp/file_of_words.out
> Input data was 4 text files >hdfs blocksize, with same word pattern plus one diff text line in each file, fourth
> file was 4 times as large as others:
> hadoop --config <config> fs -ls /tmp
> Found 5 items
> drwxr-xr-x - user hdfs 0 2011-10-20 16:17 /tmp/file_of_words.out
> -rw-r--r-- 3 user hdfs 62800021 2011-10-20 14:45 /tmp/test_file_of_words1
> -rw-r--r-- 3 user hdfs 62800024 2011-10-20 14:46 /tmp/test_file_of_words2
> -rw-r--r-- 3 user hdfs 62800024 2011-10-20 14:46 /tmp/test_file_of_words3
> -rw-r--r-- 3 user hdfs 271708312 2011-10-20 15:50 /tmp/test_file_of_words4
> Job launched 5 mappers despite spec exec set to false, output snippet:
> org.apache.hadoop.mapreduce.JobCounter
> NUM_FAILED_MAPS=1
> TOTAL_LAUNCHED_MAPS=5
> TOTAL_LAUNCHED_REDUCES=1
> RACK_LOCAL_MAPS=5
> SLOTS_MILLIS_MAPS=273540
> SLOTS_MILLIS_REDUCES=212876
> Reran same case as above only set both spec exec params to 'true', same results only this time the fifth task being
> launched is expected since spec exec = true.
> job run:
> hadoop --config <config> jar /tmp/testphw/wordcount.jar WordCount
> -Dmapreduce.job.maps.speculative.execution=true -Dmapreduce.job.reduces.speculative.execution=true
> /tmp/test_file_of_words* /tmp/file_of_words.out
> output snippet:
> org.apache.hadoop.mapreduce.JobCounter
> NUM_FAILED_MAPS=1
> TOTAL_LAUNCHED_MAPS=5
> TOTAL_LAUNCHED_REDUCES=1
> RACK_LOCAL_MAPS=5
> SLOTS_MILLIS_MAPS=279653
> SLOTS_MILLIS_REDUCES=211474
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