MATLAB: How to run the example ‘Run mapreduce on a Hadoop Cluster’

hadooplinuxmapreduceMATLAB

Hadoop version 1.2.1 Matlab version 2015a
Linux ubuntu 14.
I install Hadoop for a pseudo-distributed configuration (all of the Hadoop daemons run on a single host).
It is success to run the example 'wordcount'in Hadoop.
And it is success to read the data from the HDFS through the Matlab.
But when I try to run the example in Matlab 'Run mapreduce on a Hadoop Cluster',I failed.
It shows that the Map 0% and Reduce 0%.
There is my Matlab codes
setenv('HADOOP_HOME','/home/rjy/soft/hadoop-1.2.1');
cluster = parallel.cluster.Hadoop;
cluster.HadoopProperties('mapred.job.tracker') = 'localhost:50031';
cluster.HadoopProperties('fs.default.name') = 'hdfs://localhost:8020';
% ds = datastore('hdfs:/user/root/rrr')
outputFolder = '/home/rjy/logs/hadooplog';
mr = mapreducer(cluster);
ds = datastore('airlinesmall.csv','TreatAsMissing','NA',…
     'SelectedVariableNames','ArrDelay','ReadSize',1000);
preview(ds)
meanDelay = mapreduce(ds,@meanArrivalDelayMapper,@meanArrivalDelayReducer,mr,…
            'OutputFolder',outputFolder)
Error log is shown as follows,
Error using mapreduce (line 100)
The HADOOP job failed to complete.
Error in run_mapreduce_on_a_hadoop (line 12)
meanDelay = mapreduce(ds,@meanArrivalDelayMapper,@meanArrivalDelayReducer,mr,…
Caused by:
    The HADOOP job was not able to start MATLAB for attempt 1 of 'MAP' task 0. The user
    home directory '/homes/' for the cluster either did not exist or was not writable by
    the HADOOP user. Check the documentation on how to set the user home directory for the
    cluster.
What's the '/homes/' means? I have never seen it before. My hadoop directory is './home/rjy/soft/hadoop-1.2.1'
I wish to know how to solve this problem. I have tried many methods to solve it.
Please give me some suggestions. Thanks.

Best Answer

Hi Jingyu,
Try editing the mapred-site.xml to set the value of this property: mapreduce.admin.user.home.dir
which will be set to a value of that of your hadoop directory: './home/rjy/soft/hadoop-1.2.1'
Maybe this will force it to look to your hadoop installation instead of /homes.
Referencing: http://www.mathworks.com/matlabcentral/answers/82060-mcr-problems-with-linux-hadoop
Hope this can solve the problem.
Cheers, Esther
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