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From "Robert Joseph Evans (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (MAPREDUCE-2724) Reducer fetcher synchronize problem
Date Fri, 17 Feb 2012 17:25:59 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-2724?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Robert Joseph Evans updated MAPREDUCE-2724:
-------------------------------------------

    Status: Open  (was: Patch Available)

I am not sure if 0.21 is really supported any more.  In either case you will need to post
test results for your patch.
                
> Reducer fetcher synchronize problem
> -----------------------------------
>
>                 Key: MAPREDUCE-2724
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2724
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: task
>    Affects Versions: 0.21.0
>         Environment: ubuntu 10.10
> m64
>            Reporter: ShengpengYu
>             Fix For: 0.21.0
>
>         Attachments: patch.txt
>
>
> I've recently using hadoop(version 0.21.0) for some data processing, but sometimes reducer
crashed. Always the log is like bellow, which tells when multi fetchers recieved mapoutput
simultaneously, the merge part may fail due to some disadvantages. To verify this assumption,
I then set the number of fetchers to 1 (mapreduce.reduce.shuffle.parallelcopies), after which
the problem dispeared and the job works well.
> 2011-07-20 18:56:34,999 INFO org.apache.hadoop.mapreduce.task.reduce.EventFetcher: attempt_201107140944_0086_r_000000_0:
Got 2 new map-outputs
> 2011-07-20 18:56:35,000 INFO org.apache.hadoop.mapreduce.task.reduce.ShuffleScheduler:
Assiging dc-0005:50060 with 1 to fetcher#1
> 2011-07-20 18:56:35,000 INFO org.apache.hadoop.mapreduce.task.reduce.ShuffleScheduler:
assigned 1 of 1 to dc-0005:50060 to fetcher#1
> 2011-07-20 18:56:35,000 INFO org.apache.hadoop.mapreduce.task.reduce.ShuffleScheduler:
Assiging dc-0002:50060 with 1 to fetcher#3
> 2011-07-20 18:56:35,000 INFO org.apache.hadoop.mapreduce.task.reduce.ShuffleScheduler:
assigned 1 of 1 to dc-0002:50060 to fetcher#3
> 2011-07-20 18:56:35,006 INFO org.apache.hadoop.mapreduce.task.reduce.Fetcher: for url=50060/mapOutput?job=job_201107140944_0086&reduce=0&map=attempt_201107140944_0086_m_000498_0
sent hash and receievd reply
> 2011-07-20 18:56:35,016 INFO org.apache.hadoop.mapreduce.task.reduce.Fetcher: for url=50060/mapOutput?job=job_201107140944_0086&reduce=0&map=attempt_201107140944_0086_m_000491_0
sent hash and receievd reply
> 2011-07-20 18:56:35,056 INFO org.apache.hadoop.mapreduce.task.reduce.Fetcher: fetcher#3
about to shuffle output of map attempt_201107140944_0086_m_000498_0 decomp: 12647556 len:
12647560 to MEMORY
> 2011-07-20 18:56:35,070 INFO org.apache.hadoop.mapreduce.task.reduce.Fetcher: fetcher#1
about to shuffle output of map attempt_201107140944_0086_m_000491_0 decomp: 30172760 len:
30172764 to MEMORY
> 2011-07-20 18:56:35,553 INFO org.apache.hadoop.mapreduce.task.reduce.Fetcher: Read 12647556
bytes from map-output for attempt_201107140944_0086_m_000498_0
> 2011-07-20 18:56:35,553 INFO org.apache.hadoop.mapreduce.task.reduce.MergeManager: closeInMemoryFile
-> map-output of size: 12647556, inMemoryMapOutputs.size() -> 25
> 2011-07-20 18:56:35,553 INFO org.apache.hadoop.mapreduce.task.reduce.MergeManager: Starting
inMemoryMerger's merge since usedMemory=479526428 > mergeThreshold=440963456
> 2011-07-20 18:56:35,553 INFO org.apache.hadoop.mapreduce.task.reduce.MergeThread: InMemoryMerger
- Thread to merge in-memory shuffled map-outputs: Starting merge with 25 segments, while ignoring
0 segments
> 2011-07-20 18:56:35,554 INFO org.apache.hadoop.mapreduce.task.reduce.ShuffleScheduler:
dc-0002:50060 freed by fetcher#3 in 554s
> 2011-07-20 18:56:35,556 INFO org.apache.hadoop.mapreduce.task.reduce.MergeManager: Initiating
in-memory merge with 25 segments...
> 2011-07-20 18:56:35,557 INFO org.apache.hadoop.mapred.Merger: Merging 25 sorted segments
> 2011-07-20 18:56:35,557 INFO org.apache.hadoop.mapred.Merger: Down to the last merge-pass,
with 25 segments left of total size: 449352783 bytes
> 2011-07-20 18:56:35,696 INFO org.apache.hadoop.mapreduce.task.reduce.Fetcher: Read 30172760
bytes from map-output for attempt_201107140944_0086_m_000491_0
> 2011-07-20 18:56:35,696 INFO org.apache.hadoop.mapreduce.task.reduce.MergeManager: closeInMemoryFile
-> map-output of size: 30172760, inMemoryMapOutputs.size() -> 1
> 2011-07-20 18:56:35,696 INFO org.apache.hadoop.mapreduce.task.reduce.MergeManager: Starting
inMemoryMerger's merge since usedMemory=479526428 > mergeThreshold=440963456
> 2011-07-20 18:56:35,696 INFO org.apache.hadoop.mapreduce.task.reduce.MergeThread: InMemoryMerger
- Thread to merge in-memory shuffled map-outputs: Starting merge with 1 segments, while ignoring
0 segments
> 2011-07-20 18:56:35,696 INFO org.apache.hadoop.mapreduce.task.reduce.ShuffleScheduler:
dc-0005:50060 freed by fetcher#1 in 696s
> 2011-07-20 18:56:41,540 WARN org.apache.hadoop.mapred.Child: Exception running child
: org.apache.hadoop.mapreduce.task.reduce.Shuffle$ShuffleError: error in shuffle in InMemoryMerger
- Thread to merge in-memory shuffled map-outputs
> at org.apache.hadoop.mapreduce.task.reduce.Shuffle.run(Shuffle.java:124)
> at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:362)
> at org.apache.hadoop.mapred.Child$4.run(Child.java:217)
> at java.security.AccessController.doPrivileged(Native Method)
> at javax.security.auth.Subject.doAs(Subject.java:396)
> at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:742)
> at org.apache.hadoop.mapred.Child.main(Child.java:211)
> Caused by: java.lang.RuntimeException: java.io.EOFException
> at org.apache.hadoop.io.WritableComparator.compare(WritableComparator.java:132)
> at org.apache.hadoop.mapred.Merger$MergeQueue.lessThan(Merger.java:530)
> at org.apache.hadoop.util.PriorityQueue.downHeap(PriorityQueue.java:141)
> at org.apache.hadoop.util.PriorityQueue.adjustTop(PriorityQueue.java:108)
> at org.apache.hadoop.mapred.Merger$MergeQueue.adjustPriorityQueue(Merger.java:478)
> at org.apache.hadoop.mapred.Merger$MergeQueue.next(Merger.java:493)
> at org.apache.hadoop.mapred.Merger.writeFile(Merger.java:199)
> at org.apache.hadoop.mapreduce.task.reduce.MergeManager$InMemoryMerger.merge(MergeManager.java:443)
> at org.apache.hadoop.mapreduce.task.reduce.MergeThread.run(MergeThread.java:89)
> Caused by: java.io.EOFException
> at java.io.DataInputStream.readFully(DataInputStream.java:180)
> at java.io.DataInputStream.readFully(DataInputStream.java:152)
> at com.iflytek.hadoop.streaming.io.BaseKey32.readFields(BaseKey32.java:24)
> at org.apache.hadoop.io.WritableComparator.compare(WritableComparator.java:129)
> ... 8 more
> 2011-07-20 18:56:41,552 INFO org.apache.hadoop.mapred.Task: Runnning cleanup for the
task

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