hadoop, python, subprocess failed with code 127

Question

I'm trying to run very simple task with mapreduce.

mapper.py:

#!/usr/bin/env python
import sys
for line in sys.stdin:
    print line

my txt file:

qwerty
asdfgh
zxc

Command line to run the job:

hadoop jar /usr/lib/hadoop-0.20-mapreduce/contrib/streaming/hadoop-streaming-2.6.0-mr1-cdh5.8.0.jar \
-input /user/cloudera/In/test.txt \
-output /user/cloudera/test \
-mapper /home/cloudera/Documents/map.py \
-file /home/cloudera/Documents/map.py

Error:

INFO mapreduce.Job: Task Id : attempt_1490617885665_0008_m_000001_0, Status : FAILED
Error: java.lang.RuntimeException: PipeMapRed.waitOutputThreads(): subprocess failed with code 127
    at org.apache.hadoop.streaming.PipeMapRed.waitOutputThreads(PipeMapRed.java:325)
    at org.apache.hadoop.streaming.PipeMapRed.mapRedFinished(PipeMapRed.java:538)
    at org.apache.hadoop.streaming.PipeMapper.close(PipeMapper.java:130)
    at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:61)
    at org.apache.hadoop.streaming.PipeMapRunner.run(PipeMapRunner.java:34)
    at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:453)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:343)
    at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:164)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:415)
    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1693)
    at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158)

How to fix this and run the code? When I use cat /home/cloudera/Documents/test.txt | python /home/cloudera/Documents/map.py it works fine

!!!!!UPDATE

Something wrong with my *.py file. I have copied file from github 'tom white hadoop book' and everything is working fine.

But I cant understand what is the reason. It is not the permissions and charset (if I am not wrong). What else can it be?

Answer 1

I faced the same problem.

Issue: When the python file is created in Windows environment the new line character is CRLF. My hadoop runs on Linux which understands the newline character as LF

Solution: After changing the CRLF to LF the step ran successfully.

Answer 2

In -mapper argument you should set command, for running on cluster nodes. So there are no /home/cloudera/Documents/map.py file there. Files that you pass with -files option are placed in working directory, so you can simply use it in this way: ./map.py

I don't remember what permissions are set to this file, so if there are no execute permissions use it as python map.py

so the full command is

hadoop jar /usr/lib/hadoop-0.20-mapreduce/contrib/streaming/hadoop-streaming-2.6.0-mr1-cdh5.8.0.jar \
-input /user/cloudera/In/test.txt \
-output /user/cloudera/test \
-mapper "python map.py" \
-file /home/cloudera/Documents/map.py