[Pacemaker] master/slave or unique clones

[Maros Timko]

> So, application acts as "master" if it was able to bind to the pre-configured IP and as a "node" if it wasn't. If it's a master it listens on an additional port and receives updates from nodes. Each application pulls video feed out of attached video cameras and stores them on the local drives, that what makes them unique.
>
> What I want to achieve:
>
> 1. Have "master" IP running on one of the 2 servers (attached to shared EMC storage)
> 2. Have "master" app started on "master" IP and insure it's running.
> 3. Start application on each node and make sure it's running.
>
> Hopefully this clears the landscape a bit :)
>

Looks pretty straight-forward. You just need to decompose your
preference computation logic from start of the resource. Pacemaker
should decide where to promote the resource, you have to provide him
score from all nodes.
Check ocf:linbit:drbd for inspirations.

Tino