[ClusterLabs] Moving a resource when another resource fails

[john tillman]

Good day all,

I'm trying to set up my cluster such that when mysql can't run, my VIP
will move to another node with a working mysql.  I'm trying to do this
with a location constraint but can't quite figure out the syntax.

I have a resource myVIP.
simple VIP resource.  It only runs on one node at a time.  My applications
connect through it to the database.

I have a resource myDB-clone that runs on two nodes.  It is simply a
mysqld resource, cloned to the two nodes I need it on.

FYI, behind the scenes I have a master-master replication configuration
but I use the VIP so that all writes go to the same DB.

According to the man page for pcs setting up the rule for this constraint
requires an "expression" (or more then one).  That's where I'm having the
problem.

My pcs command looks like:

pcs  constraint  location  myVIP  rule  constraint-id=Rule1 
score=-INFINITY  <insert expression here>
the expression I'm looking for is one that will determine if mysqld,
myDB-clone, is running on this node and if it is not then have the
-INFINITY score applied and move myVIP to the other node.

Any help/suggestions would be appreciated.

-John