Mahout runs out of heap space

问题

I am running NaiveBayes on a set of tweets using Mahout. Two files, one 100 MB and one 300 MB. I changed JAVA_HEAP_MAX to JAVA_HEAP_MAX=-Xmx2000m ( earlier it was 1000). But even then, mahout ran for a few hours ( 2 to be precise) before it complained of heap space error. What should i do to resolve ?

Some more info if it helps : I am running on a single node, my laptop infact and it has 3GB of RAM (only) .

Thanks.

EDIT: I ran it the third time with <1/2 of the data that i used the first time ( first time i used 5.5 million tweets, second i used 2million ) and i still got a heap space problem. I am posting the complete error for completion purposes :

17 May, 2011 2:16:22 PM
 org.apache.hadoop.mapred.JobClient monitorAndPrintJob
INFO:  map 50% reduce 0%

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
    at java.lang.AbstractStringBuilder.<init>(AbstractStringBuilder.java:62)
    at java.lang.StringBuilder.<init>(StringBuilder.java:85)
    at org.apache.hadoop.mapred.JobClient.monitorAndPrintJob(JobClient.java:1283)
    at org.apache.hadoop.mapred.JobClient.runJob(JobClient.java:1251)
    at org.apache.mahout.classifier.bayes.mapreduce.common.BayesFeatureDriver.runJob(BayesFeatureDriver.java:63)
    at org.apache.mahout.classifier.bayes.mapreduce.bayes.BayesDriver.runJob(BayesDriver.java:44)
    at org.apache.mahout.classifier.bayes.TrainClassifier.trainNaiveBayes(TrainClassifier.java:54)
    at org.apache.mahout.classifier.bayes.TrainClassifier.main(TrainClassifier.java:162)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:616)
    at org.apache.hadoop.util.ProgramDriver$ProgramDescription.invoke(ProgramDriver.java:68)
    at org.apache.hadoop.util.ProgramDriver.driver(ProgramDriver.java:139)
    at org.apache.mahout.driver.MahoutDriver.main(MahoutDriver.java:184)
17 May, 2011 7:14:53 PM org.apache.hadoop.mapred.LocalJobRunner$Job run
WARNING: job_local_0001
java.lang.OutOfMemoryError: Java heap space
    at java.lang.String.substring(String.java:1951)
    at java.lang.String.subSequence(String.java:1984)
    at java.util.regex.Pattern.split(Pattern.java:1019)
    at java.util.regex.Pattern.split(Pattern.java:1076)
    at org.apache.mahout.classifier.bayes.mapreduce.common.BayesFeatureMapper.map(BayesFeatureMapper.java:78)
    at org.apache.mahout.classifier.bayes.mapreduce.common.BayesFeatureMapper.map(BayesFeatureMapper.java:46)
    at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:50)
    at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:358)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:307)
    at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:177)

And i am posting the part of the bin/mahout script that i changed : Original :

JAVA=$JAVA_HOME/bin/java
            JAVA_HEAP_MAX=-Xmx1000m 

if [ "$MAHOUT_HEAPSIZE" != "" ]; then
  #echo "run with heapsize $MAHOUT_HEAPSIZE"
  JAVA_HEAP_MAX="-Xmx""$MAHOUT_HEAPSIZE""m"
  #echo $JAVA_HEAP_MAX
fi

Modified :

JAVA=$JAVA_HOME/bin/java
 JAVA_HEAP_MAX=-Xmx2000m 


if [ "$MAHOUT_HEAPSIZE" != "" ]; then
  #echo "run with heapsize $MAHOUT_HEAPSIZE"
  JAVA_HEAP_MAX="-Xmx""$MAHOUT_HEAPSIZE""m"
  #echo $JAVA_HEAP_MAX
fi

回答1:

You're not specifying what process ran out of memory, which is important. You need to set MAHOUT_HEAPSIZE, not whatever JAVA_HEAP_MAX is.

回答2:

Did you modify the heap size for the hadoop environment or the mahout one? See if this query on mahout list helps. From personal experience, I can suggest that you reduce the data size that you are trying to process. Whenever I tried to execute the Bayes classifier on my laptop, after running for a few hours, the heap space would get exhausted.

I'd suggest that you run this off EC2. I think the basic S3/EC2 option is free for usage.

回答3:

When you start mahout process, you can runn "jps" it will show all the java process running on your machine with your user-id. "jps" will return you a process-id. You can find the process and can run "jmap -heap process-id" to see your heap space utilization.

With this approach you can estimate at which part of your processing memory is exhausted and where you need to increase.

来源：https://stackoverflow.com/questions/6026015/mahout-runs-out-of-heap-space

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mahout