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https://issues.apache.org/jira/browse/MAPREDUCE-1171?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Amareshwari Sriramadasu updated MAPREDUCE-1171:
-----------------------------------------------
Attachment: patch-1171.txt
Patch adding the suggested config variables.
Tested the patch manually by simulating read timeout and verified with
configuration "mapreduce.reduce.shuffle.notify.readerror" set to true, the
fetch failure is notified after "mapreduce.reduce.shuffle.maxfetchfailures".
With "mapreduce.reduce.shuffle.notify.readerror" set to false, it is notified
immediately after the failure.
> Lots of fetch failures
> ----------------------
>
> Key: MAPREDUCE-1171
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-1171
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: task
> Affects Versions: 0.21.0
> Reporter: Christian Kunz
> Assignee: Amareshwari Sriramadasu
> Priority: Blocker
> Fix For: 0.21.0
>
> Attachments: patch-1171.txt
>
>
> Since we upgraded to hadoop-0.20.1 from hadoop0.18.3, we see lot of more map
> task failures because of 'Too many fetch-failures'.
> One of our jobs makes hardly any progress, because of 3000 reduces not able
> to get map output of 2 trailing maps (with about 80GB output each), which
> repeatedly are marked as failures because of reduces not being able to get
> their map output.
> One difference to hadoop-0.18.3 seems to be that reduce tasks report a failed
> mapoutput fetch even after a single try when it was a read error
> (cr.getError().equals(CopyOutputErrorType.READ_ERROR). I do not think this is
> a good idea, as trailing map tasks will be attacked by all reduces
> simultaneously.
> Here is a log output of a reduce task:
> {noformat}
> 2009-10-29 21:38:36,148 WARN org.apache.hadoop.mapred.ReduceTask:
> attempt_200910281903_0028_r_000000_0 copy failed:
> attempt_200910281903_0028_m_002781_1 from some host
> 2009-10-29 21:38:36,148 WARN org.apache.hadoop.mapred.ReduceTask:
> java.net.SocketTimeoutException: Read timed out at
> java.net.SocketInputStream.socketRead0(Native Method)
> at java.net.SocketInputStream.read(SocketInputStream.java:129)
> at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
> at java.io.BufferedInputStream.read1(BufferedInputStream.java:258)
> at java.io.BufferedInputStream.read(BufferedInputStream.java:317)
> at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:687)
> at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:632)
> at
> sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1064)
> at
> org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.getInputStream(ReduceTask.java:1496)
> at
> org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.getMapOutput(ReduceTask.java:1377)
> at
> org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.copyOutput(ReduceTask.java:1289)
> at
> org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.run(ReduceTask.java:1220)
> 2009-10-29 21:38:36,149 INFO org.apache.hadoop.mapred.ReduceTask: Task
> attempt_200910281903_0028_r_000000_0: Failed fetch #1 from
> attempt_200910281903_0028_m_002781_1
> 2009-10-29 21:38:36,149 INFO org.apache.hadoop.mapred.ReduceTask: Failed to
> fetch map-output from attempt_200910281903_0028_m_002781_1 even after
> MAX_FETCH_RETRIES_PER_MAP retries... or it is a read error, reporting to
> the JobTracker.
> {noformat}
> Also I saw a few log messages which look suspicious as if successfully
> fetched map output is discarded because of the map being marked as failed
> (because of too many fetch failures). This would make the situation even
> worse.
> {noformat}
> 2009-10-29 22:07:28,729 INFO org.apache.hadoop.mapred.ReduceTask: header:
> attempt_200910281903_0028_m_001076_0, compressed len: 21882555, decompressed
> len: 23967845
> 2009-10-29 22:07:28,729 INFO org.apache.hadoop.mapred.ReduceTask: Shuffling
> 23967845 bytes (21882555 raw bytes) into RAM from
> attempt_200910281903_0028_m_001076_0
> 2009-10-29 22:07:43,602 INFO org.apache.hadoop.mapred.ReduceTask: Read
> 23967845 bytes from map-output for attempt_200910281903_0028_m_001076_0
> 2009-10-29 22:07:43,602 INFO org.apache.hadoop.mapred.ReduceTask: Rec #1 from
> attempt_200910281903_0028_m_001076_0 -> (20, 39772) from some host
> ...
> 2009-10-29 22:10:07,220 INFO org.apache.hadoop.mapred.ReduceTask: Ignoring
> obsolete output of FAILED map-task: 'attempt_200910281903_0028_m_001076_0'
> {noformat}
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