pcs needs to reflect this in resource defaults.


bz1891929 comment 8:
--- Additional comment from Ken Gaillot on 2020-11-06 22:24:49 UTC ---

After further investigation, we determined that it is correct but undocumented behavior that node attribute expressions are not supported for *meta-attributes*, except in the context of an operation or operation defaults. Node attribute expressions do not work with meta-attributes in a resource's configuration, resource defaults, or cluster properties.

Node attribute expressions should work for resource options (instance attributes), whether in the resource configuration or resource defaults, so it is correct that pcs allows node attribute expressions in resource defaults. (That can be used in testing the original bz.) It would probably be a good idea for pcs to reject the combination of meta and node attribute rules for resource defaults.

This makes sense when you consider that only an operation is directly associated with a single node. Most meta-attributes would make no sense being node-specific (target-role, allow-migrate, etc.). While some might (resource-stickiness, migration-threshold), that would be an unusual use case, and I'd rather wait until there is customer demand before formalizing that as an RFE.

I'm not sure whether this needs to be documented in RHEL. I believe rules are currently documented only in the context of location constraints (https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/configuring_and_managing_high_availability_clusters/assembly_determining-resource-location-with-rules-configuring-and-managing-high-availability-clusters) so there's no existing place for it. Possibly the pcs man page could be updated for "pcs resource defaults".

Pacemaker should enforce proper rule syntax usage more strictly via its XML schema, but for compatibility reasons that is not feasible in the RHEL 8 time frame.