[Pacemaker] location constraint "anywhere" on asymmetric cluster

[Andrew Beekhof]

On Thu, Jan 31, 2013 at 1:02 AM, Brian J. Murrell <brian at interlinx.bc.ca> wrote:
> I'm experimenting with asymmetric clusters and resource location
> constraints.
>
> My cluster has some resources which have to be restricted to certain
> nodes and other resources which can run on any node.  Given that, an
> "opt-in" cluster seems the most manageable.  That is, it seems easier to
> create constraints based on where things should run (i.e. a whitelist)
> rather than having to maintain lists of where things shouldn't run
> (blacklists).
>
> I wonder though for the case of a resource that can run anywhere, if
> there is any more elegant way to specify that in an asymmetric cluster
> other than creating an expression using something like the "#uname"
> attribute with an operation of "ne" and specifying a host that doesn't
> exist for the expression's "value".


You can also use an operation of "defined". No dummy value needed in that case.

>
> Of course other attributes could be used in a negative fashion such as
> this but I wonder if there is a more "positive" syntax to express
> "anywhere".  Ideally, I'd like the expression to be absolutely clear
> that it's intention is to allow the resource to run "anywhere" rather
> than the reader having to deduce that by knowing that the node specified
> doesn't exist.
>
> Alternatively, if there is a way to "whitelist" (i.e. meaning not having
> to create and maintain a list of where not to run a resource) where
> resources can run on a symmetric cluster that might be an acceptable
> alternative.
>
> Cheers,
> b.
>
>
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