FAQ
Hi,
I have running map-reduce task on huge data on 40 Quad Core(16GB RAM)
Machine hadoop cluster. As my mapper machines sufficiently run on 1GB heap
size. I had set map reduce tasks heap size to 1GB. And, total number of
tasks per node is set to 9 ( 5 map tasks and 4 reduce tasks). It took huge
amount of time and finally after mapper completed 98%, the job failed with
below error:

java.lang.OutOfMemoryError: Java heap space
at
org.apache.hadoop.io.DataOutputBuffer$Buffer.write(DataOutputBuffer.java:52)
at org.apache.hadoop.io.DataOutputBuffer.write(DataOutputBuffer.java:90)
at
org.apache.hadoop.io.SequenceFile$Reader.nextRawKey(SequenceFile.java:1974)
at
org.apache.hadoop.io.SequenceFile$Sorter$SegmentDescriptor.nextRawKey(SequenceFile.java:3002)
at
org.apache.hadoop.io.SequenceFile$Sorter$MergeQueue.merge(SequenceFile.java:2802)
at org.apache.hadoop.io.SequenceFile$Sorter.merge(SequenceFile.java:2511)
at
org.apache.hadoop.mapred.MapTask$MapOutputBuffer.mergeParts(MapTask.java:1040)
at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.flush(MapTask.java:698)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:220)
at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:2124)

I am not able to figure out where things went wrong. Can some one please
help me in this?

Thanks
Pallavi

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  • Jason Venner at Aug 28, 2008 at 3:21 pm
    We have occasionally seen that when there is either damage to the
    sequence file or there was a read error.

    What is happening is that the object size to be read is garbage, and the
    system trys to allocate 2^32 bytes to de-serialize the object.

    In our case the .crc file was not catching the damage, but I don't
    recall the reason why at present, as it was some months back that we had
    trouble with this.


    Pallavi Palleti wrote:
    Hi,
    I have running map-reduce task on huge data on 40 Quad Core(16GB RAM)
    Machine hadoop cluster. As my mapper machines sufficiently run on 1GB heap
    size. I had set map reduce tasks heap size to 1GB. And, total number of
    tasks per node is set to 9 ( 5 map tasks and 4 reduce tasks). It took huge
    amount of time and finally after mapper completed 98%, the job failed with
    below error:

    java.lang.OutOfMemoryError: Java heap space
    at
    org.apache.hadoop.io.DataOutputBuffer$Buffer.write(DataOutputBuffer.java:52)
    at org.apache.hadoop.io.DataOutputBuffer.write(DataOutputBuffer.java:90)
    at
    org.apache.hadoop.io.SequenceFile$Reader.nextRawKey(SequenceFile.java:1974)
    at
    org.apache.hadoop.io.SequenceFile$Sorter$SegmentDescriptor.nextRawKey(SequenceFile.java:3002)
    at
    org.apache.hadoop.io.SequenceFile$Sorter$MergeQueue.merge(SequenceFile.java:2802)
    at org.apache.hadoop.io.SequenceFile$Sorter.merge(SequenceFile.java:2511)
    at
    org.apache.hadoop.mapred.MapTask$MapOutputBuffer.mergeParts(MapTask.java:1040)
    at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.flush(MapTask.java:698)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:220)
    at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:2124)

    I am not able to figure out where things went wrong. Can some one please
    help me in this?

    Thanks
    Pallavi
    --
    Jason Venner
    Attributor - Program the Web <http://www.attributor.com/>
    Attributor is hiring Hadoop Wranglers and coding wizards, contact if
    interested

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postedAug 28, '08 at 3:04p
activeAug 28, '08 at 3:21p
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