On 11/30/2010 at 10:11 AM, Alan Jones <falanclus...@gmail.com> wrote: > On Thu, Nov 25, 2010 at 6:32 AM, Tim Serong <tser...@novell.com> wrote: > > Can you elaborate on why you want this particular behaviour? Maybe > > there's some other way to approach the problem? > > I have explained the issue as clearly as I know how. The problem is > fundamental > to the design of the policy engine in Pacemaker. It performs only two > passes to > resolve constraints, when what is required for general purpose > constraint resolution > is an iterative model. These problems have been addressed in the literature > for > decades.
What I meant by "maybe there's some other way to approach the problem" is "maybe there's some other way we can figure out how to get something *like* the behaviour you desire, given the fact that Pacemaker's colocation constraints behave the way they do". If you have: primitive resX ocf:pacemaker:Dummy primitive resY ocf:pacemaker:Dummy location resX-loc resX 1: nodeA.acme.com location resY-loc resY 1: nodeB.acme.com colocation resX-resY -2: resX resY And you have "-inf constraints coming from an external source", as you said before, can you change the external source so that it generates different constraints? e.g., instead of generating either of: location resX-nodeA resX -inf: nodeA.acme.com location resY-nodeB resY -inf: nodeB.acme.com (where only the second one works, because of the dependency inherent in the colocation contraint) can your external source specify these constraints only in terms of resY, which is the one that's capable of "dragging" resX around the place? e.g.: location resX-nodeA resY inf: nodeA.acme.com location resY-nodeB resY -inf: nodeB.acme.com Or, if that sounds completely deranged, how about this: On the assumption your "external source" will only ever inject one -inf rule, for one resource, why not make it change the colocation constraint as well? e.g.: generate either of: location resX-nodeA resX -inf: nodeA.acme.com colocation resY-resX -2: resY resX (and delete resX-resY if present) -- or -- location resY-nodeB resY -inf: nodeB.acme.com colocation resX-resY -2: resX resY (and delete resY-resX if present) Are there any more details about your application you can share? Regards, Tim -- Tim Serong <tser...@novell.com> Senior Clustering Engineer, OPS Engineering, Novell Inc. _______________________________________________ Pacemaker mailing list: Pacemaker@oss.clusterlabs.org http://oss.clusterlabs.org/mailman/listinfo/pacemaker Project Home: http://www.clusterlabs.org Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf Bugs: http://developerbugs.linux-foundation.org/enter_bug.cgi?product=Pacemaker
