Debugging YARN Applications

List Applications Running on Cluster

yarn application -list

Looking at Logs of an Application

Simply type:

yarn logs -applicationId

Looking at the Container Subdirectory

su - root

ls -la [yarn_nodemanager_dir]/usercache/[username]/appcache/

Looks like:

[root@localhost ~]# ls -la /yarn/nm/usercache/cloudera/appcache/ total 20 drwx--x--- 5 yarn yarn 4096 May 3 18:30 . drwxr-x--- 4 yarn yarn 4096 Apr 29 01:48 .. drwx--x--- 4 yarn yarn 4096 May 3 17:34 application_1399163605439_0001 drwx--x--- 4 yarn yarn 4096 May 3 17:34 application_1399163605439_0002 drwx--x--- 2 yarn yarn 4096 May 3 18:08 application_1399163811192_0002

Then look inside the subdirectories for each application.

Looking at the Container Run Script

Look inside the Container subdirectory and then find a container subdirectory. Inside there you'll see a launch_container.sh bash script which will reference all of you files and conf values to run the master or worker process. It's a nice way to see what is going on at the worker process level.