YARN is fantastic runtime environment for running various workflows but when things don’t work excatly as it was planned, it may be a little bit of a tedious process to find out what went wrong. This section tries to provide instructions how to troubleshoot various issues causing abnormal behaviour.

When something is about to get launched into yarn, a generic procedure goes like this:

There are various places where things can go wrong in this flow:

Log files are the most obvious place to look errors. YARN application itself writes log files name Appmaster.stdout, Appmaster.stderr, Container.stdout and Container.stderr under yarn’s application logging directory. Also yarn’s own logs for Resource Manager and especially for Node Manager contains additional information when i.e. containers are getting killed by yarn itself.