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https://issues.apache.org/jira/browse/MAPREDUCE-6357?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dustin Cote updated MAPREDUCE-6357:
-----------------------------------
Attachment: MAPREDUCE-6357-1.patch
Fixing a typo and checkstyle warning. No tests since this is a doc change.
> MultipleOutputs.write() API should document that output committing is not
> utilized when input path is absolute
> --------------------------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-6357
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-6357
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: documentation
> Affects Versions: 2.6.0
> Reporter: Ivan Mitic
> Assignee: Dustin Cote
> Attachments: MAPREDUCE-6357-1.patch
>
>
> After spending the afternoon debugging a user job where reduce tasks were
> failing on retry with the below exception, I think it would be worthwhile to
> add a note in the MultipleOutputs.write() documentation, saying that absolute
> paths may cause improper execution of tasks on retry or when MR speculative
> execution is enabled.
> {code}
> 2015-04-28 23:13:10,452 WARN [main] org.apache.hadoop.mapred.YarnChild:
> Exception running child : java.io.IOException: File already
> exists:wasb://full20150...@bgtstoragefull.blob.core.windows.net/user/hadoop/some/path/block-r-00299.bz2
> at
> org.apache.hadoop.fs.azure.NativeAzureFileSystem.create(NativeAzureFileSystem.java:1354)
> at
> org.apache.hadoop.fs.azure.NativeAzureFileSystem.create(NativeAzureFileSystem.java:1195)
> at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:908)
> at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:889)
> at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:786)
> at
> org.apache.hadoop.mapreduce.lib.output.TextOutputFormat.getRecordWriter(TextOutputFormat.java:135)
> at
> org.apache.hadoop.mapreduce.lib.output.MultipleOutputs.getRecordWriter(MultipleOutputs.java:475)
> at
> org.apache.hadoop.mapreduce.lib.output.MultipleOutputs.write(MultipleOutputs.java:433)
> at
> com.ancestry.bigtree.hadoop.LevelReducer.processValue(LevelReducer.java:91)
> at
> com.ancestry.bigtree.hadoop.LevelReducer.reduce(LevelReducer.java:69)
> at
> com.ancestry.bigtree.hadoop.LevelReducer.reduce(LevelReducer.java:14)
> at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:171)
> at
> org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:627)
> at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:389)
> at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:163)
> at java.security.AccessController.doPrivileged(Native Method)
> at javax.security.auth.Subject.doAs(Subject.java:415)
> at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1628)
> at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158)
> {code}
> As discussed in MAPREDUCE-3772, when the baseOutputPath passed to
> MultipleOutputs.write() is an absolute path (or more precisely a path that
> resolves outside of the job output-dir), the concept of output committing is
> not utilized.
> In this case, the user read thru the MultipleOutputs docs and was assuming
> that everything will be working fine, as there are blog posts saying that
> MultipleOutputs does handle output commit.
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