Determine which server in inventory is the executor

[Eric Brewer]

I have a situation where i need to be able to load new packages on a server, and turn it into an nfs yum repo.  I have a playbook that does this, and mounts the directory the repo will live on to the other servers and sets up all the required repo files.  The only thing I am struggling with, is how to programmaticly determine which one of the servers in my inventory is the executor on any given run, so I can set the ip of the executor as the mount ip on all of the other servers. And the goal of this is full automation, so I can't go in and set a variable manually, and I was wondering if anyone had any ideas?

Thanks in advance!