[ClusterLabs] Potential deprecation: Node-attribute-based rules in operation meta-attributes

[Ken Gaillot]

Hi all,

I have recently been cleaning up Pacemaker's rule code, and came across
an inconsistency.

Currently, meta-attributes may have rules with date/time-based
expressions (the <date_expression> element). Node attribute
expressions (the <expression> element) are not allowed, with the
exception of operation meta-attributes (beneath an <op> or
<op_defaults> element).

I'd like to deprecate support for node attribute expressions for
operation meta-attributes in Pacemaker 2.1.8, and drop support in
3.0.0.

I don't think it makes sense to vary meta-attributes by node. For
example, if a clone monitor has on-fail="block" (to cease all actions
on instances everywhere) on one node and on-fail="stop" (to stop all
instances everywhere) on another node, what should the cluster do if
monitors fail on both nodes? It seems to me that it's more likely to be
confusing than helpful.

If anyone has a valid use case for node attribute expressions for
operation meta-attributes, now is the time to speak up!
-- 
Ken Gaillot <kgaillot at redhat.com>