[Pacemaker] master/slave or unique clones

[Vadym Chepkov]

Hi,

I want to convert our home-made application to be managed by pacemaker cluster. 
The way it works now: application starts, discovers all IPs configured on the system and if it sees preconfigured IP it becomes "master" and will serve configuration requests, 
if not - "node" and will try to connect to "master" node to get configuration data. Other then that, application instances are absolutely the same on all "cluster" servers and 
they start collecting their own unique data.

I started to write a resource agent in "stateful" manner, but the problem is - I can't promote or demote and the documentation says : application has to start in "slave" mode, 
which I can't supply. So I thought of unique clones instead, but I need to create collocation/ordering constraint with IP for the clone:0 and again documentation says I shouldn't do it.

As a workaround I could probably create a separate "master" instance and clones with clone-max=node-1 and create -INFINITY collocation constraint between them, but it's more of a hack it seems.

What would Andrew do ? :)

Thank you,
Vadym Chepkov