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From Bradford Stephens <bradfordsteph...@gmail.com>
Subject Re: java.lang.OutOfMemoryError: GC overhead limit exceeded
Date Sun, 26 Sep 2010 08:00:29 GMT
I'm going to try running it on high-RAM boxes with -Xmx4096m or so,
see if that helps.

On Sun, Sep 26, 2010 at 12:55 AM, Bradford Stephens
<bradfordstephens@gmail.com> wrote:
> Greetings,
>
> I'm running into a brain-numbing problem on Elastic MapReduce. I'm
> running a decent-size task (22,000 mappers, a ton of GZipped input
> blocks, ~1TB of data) on 40 c1.xlarge nodes (7 gb RAM, ~8 "cores").
>
> I get failures randomly --- sometimes at the end of my 6-step process,
> sometimes at the first reducer phase, sometimes in the mapper. It
> seems to fail in multiple areas. Mostly in the reducers. Any ideas?
>
> Here's the settings I've changed:
> -Xmx400m
> 6 max mappers
> 1 max reducer
> 1GB swap partition
> mapred.job.reuse.jvm.num.tasks=50
> mapred.reduce.parallel.copies=3
>
>
> java.lang.OutOfMemoryError: GC overhead limit exceeded
>        at java.nio.CharBuffer.wrap(CharBuffer.java:350)
>        at java.nio.CharBuffer.wrap(CharBuffer.java:373)
>        at java.lang.StringCoding$StringDecoder.decode(StringCoding.java:138)
>        at java.lang.StringCoding.decode(StringCoding.java:173)
>        at java.lang.String.(String.java:443)
>        at java.lang.String.(String.java:515)
>        at org.apache.hadoop.io.WritableUtils.readString(WritableUtils.java:116)
>        at cascading.tuple.TupleInputStream.readString(TupleInputStream.java:144)
>        at cascading.tuple.TupleInputStream.readType(TupleInputStream.java:154)
>        at cascading.tuple.TupleInputStream.getNextElement(TupleInputStream.java:101)
>        at cascading.tuple.hadoop.TupleElementComparator.compare(TupleElementComparator.java:75)
>        at cascading.tuple.hadoop.TupleElementComparator.compare(TupleElementComparator.java:33)
>        at cascading.tuple.hadoop.DelegatingTupleElementComparator.compare(DelegatingTupleElementComparator.java:74)
>        at cascading.tuple.hadoop.DelegatingTupleElementComparator.compare(DelegatingTupleElementComparator.java:34)
>        at cascading.tuple.hadoop.DeserializerComparator.compareTuples(DeserializerComparator.java:142)
>        at cascading.tuple.hadoop.GroupingSortingComparator.compare(GroupingSortingComparator.java:55)
>        at org.apache.hadoop.mapred.Merger$MergeQueue.lessThan(Merger.java:373)
>        at org.apache.hadoop.util.PriorityQueue.downHeap(PriorityQueue.java:136)
>        at org.apache.hadoop.util.PriorityQueue.adjustTop(PriorityQueue.java:103)
>        at org.apache.hadoop.mapred.Merger$MergeQueue.adjustPriorityQueue(Merger.java:335)
>        at org.apache.hadoop.mapred.Merger$MergeQueue.next(Merger.java:350)
>        at org.apache.hadoop.mapred.Merger.writeFile(Merger.java:156)
>        at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$InMemFSMergeThread.doInMemMerge(ReduceTask.java:2645)
>        at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$InMemFSMergeThread.run(ReduceTask.java:2586)
>
> --
> Bradford Stephens,
> Founder, Drawn to Scale
> drawntoscalehq.com
> 727.697.7528
>
> http://www.drawntoscalehq.com --  The intuitive, cloud-scale data
> solution. Process, store, query, search, and serve all your data.
>
> http://www.roadtofailure.com -- The Fringes of Scalability, Social
> Media, and Computer Science
>



-- 
Bradford Stephens,
Founder, Drawn to Scale
drawntoscalehq.com
727.697.7528

http://www.drawntoscalehq.com --  The intuitive, cloud-scale data
solution. Process, store, query, search, and serve all your data.

http://www.roadtofailure.com -- The Fringes of Scalability, Social
Media, and Computer Science

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