Hadoop Streaming using python

Question

I am trying to execute the map reduce code as below:

hadoop jar /usr/lib/Hadoop/Hadoop-streaming-0.20.2-cdh3u2.jar –file mapper.py –mapper mapper.py –file reducer.py – reducer reducer.py –input /user/training/samplypy.txt –ouput /user/training/pythonMR/output

getting below exception -

Exception in thread "main" java.lang.ClassNotFoundException: –file
 at java.net.URLClassLoader1ドル.run(URLClassLoader.java:366)
 at java.net.URLClassLoader1ドル.run(URLClassLoader.java:355)
 at java.security.AccessController.doPrivileged(Native Method)
 at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
 at java.lang.Class.forName0(Native Method)
 at java.lang.Class.forName(Class.java:264)
 at org.apache.hadoop.util.RunJar.main(RunJar.java:149)

I am using Hadoop 1.0.3. I've tried with multiple versions of hadoop-streaming jar like:

hadoop-streaming-0.20.2-cdh3u2.jar 
hadoop-streaming-1.2.0.jar 
hadoop-streaming.jar

• suztomo: Where is the document that tells you to run these command?
• user2046117: Have you got your $HADOOP_HOME env variable set?
• srikanth: Refer this, stackoverflow.com/questions/16701979/….

Answer 1

1. One thing I can tell is that you did not use full path for '-file' statement:

   –file /mapper/location/mapper.py (use full path with the file name here)

   –mapper mapper.py (correct, mapper file name only)

   –file /reducer/location/reducer.py (use full path with the file name here)

   – reducer reducer.py (correct, reducer file name only)

2. make sure your -input and -output are pointing to HDFS not local path

Here is the code I used:

hadoop jar /opt/cloudera/parcels/hadoop-streaming.jar \
-D mapred.reduce.tasks=15 -D stream.map.input.field.separator=',' -D stream.map.output.field.separator=',' \
-D mapred.textoutputformat.separator=',' \
-input /user/temp/in/ \
-output /user/temp/out \
-file /app/qa/python/mapper.py \
-mapper mapper.py \
-file /app/qa/python/reducer.py \
-reducer reducer.py