My PHP server is hosted on Job Tracker machine and I am trying to run the map reduce job through my web page by calling the command line executing the jar command,
but I am getting no response and job is not starting.
However if I run a command to list the hdfs using same methodology it is running fine. Please guide me.
Following command is not responding me anything and job is not running:
exec("HADOOP_DIR/bin/hadoop jar /usr/local/MapReduce.jar Mapreduce [input Path] [output Path]");
But if I do this:
exec("HADOOP_DIR/bin/hadoop dfs -ls /user/hadoop");
It is running fine.
I solved this problem by changing the php server user to hduser (user which has permission to write files in hdfs). without changing this user only the commands which reads from the hdfs were working and not the one which needs to create the files or write on hdfs.
When i tried to run the command for creating the directory in hdfs through my php script, I got the following error in my php server logs (/var/log/apache2/error.log):
mkdir: org.apache.hadoop.security.AccessControlException: Permission denied: user=www-data, access=WRITE, inode="hduser":hduser:supergroup:rwxr-xr-x
And on running the Jar command to trigger MapRed program I got the following error:
Exception in thread "main" java.io.IOException: Permission denied
at java.io.UnixFileSystem.createFileExclusively(Native Method)
at java.io.File.createTempFile(File.java:1879)
at org.apache.hadoop.util.RunJar.main(RunJar.java:115)
Then what i did is i changed the user in /etc/apache2/apache2.conf to my hadoop user and then restarted my server and every thing was working fine now.
I should reference Execute hadoop jar from PHP Server fails. Permission denied post which helped me alot in solving this problem. I hope this post helps others too.
