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https://issues.apache.org/jira/browse/AVRO-847?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Doug Cutting reassigned AVRO-847:
---------------------------------
Assignee: Jeremy Lewi
> Unittest for tethered map reduce in java
> ----------------------------------------
>
> Key: AVRO-847
> URL: https://issues.apache.org/jira/browse/AVRO-847
> Project: Avro
> Issue Type: Test
> Components: java
> Affects Versions: 1.6.0
> Reporter: Jeremy Lewi
> Assignee: Jeremy Lewi
> Priority: Minor
> Labels: patch
> Attachments: AVRO-847.patch, AVRO-PATCH-847-1
>
>
> I was working on a unittest to run the java example of a tethered map reduce
> job (see Issue #512). While doing so I ran into a couple of issues. I was
> able to work around the issues and will submit a patch but I'm not sure my
> fixes were correct. The issues are below.
> 1) A deadlock appears to occur if the subprocess can't start. This happens
> because the parent process is waiting for the childProcess to send the
> configure command, which it can't do if the process failed to start. I solved
> this by adding some code to TetheredProcess to check if the subprocess has
> already exited.
> 2) The tethered classes don't provide a way to pass command line arguments to
> the program executed to start the subprocess. I solved this by adding some
> appropriate keys to the job configuration XML file to specify a) the
> executable, b) the command line arguments and c) whether or not the
> executable should be distributed via the DistributeCache mechanism to all the
> nodes.
> 3) I ran into some communication problems between the child and parent
> processes. These seemed to be because the child was using "Sasl" for the
> protocol but the parent was using "Socket" (e.g SocketServer,
> SocketTransciever).
> 4) In TetherJob.setupJob I needed to set the MapOutputKeyClass to TetherData;
> otherwise I was getting an error about the mapper expecting type AvroKey for
> the data but getting type TetherData.
> 5) During the sort phase when it called compare on the keys I was getting an
> exception (stack trace below). I think this is because the buffer collecting
> the output from the mapper wasn't being flushed. I was able to "solve" this
> problem by forcing a flush in TetherKeySerializer.serialize. My limited
> knowledge of the innards of map/reduce avro lead me to believe this is a less
> than ideal solution. I would imagine that during the M/R job, a flush should
> be occurring at the end of the map phase and that should make it unnecessary
> to invoke flush each time serialize is invoked.
> org.apache.avro.AvroRuntimeException: java.io.EOFException
> at org.apache.avro.io.BinaryData.compare(BinaryData.java:74)
> at
> org.apache.avro.mapred.tether.TetherKeyComparator.compare(TetherKeyComparator.java:46)
>
> at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.compare(MapTask.java:942)
> at org.apache.hadoop.util.QuickSort.fix(QuickSort.java:30)
> at org.apache.hadoop.util.QuickSort.sortInternal(QuickSort.java:83)
> at org.apache.hadoop.util.QuickSort.sort(QuickSort.java:59)
> at
> org.apache.hadoop.mapred.MapTask$MapOutputBuffer.sortAndSpill(MapTask.java:1228)
>
> at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.flush(MapTask.java:1129)
> at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:359)
> at org.apache.hadoop.mapred.MapTask.run(MapTask.java:307)
> at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:177)
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