[ClusterLabs] Coming in Pacemaker 2.0.5: finer control over resource and operation defaults

[Ken Gaillot]

Hi all,

Pacemaker 2.0.4 is barely out the door, and we're already looking ahead
to 2.0.5, expected at the end of this year.

One of the new features, already available in the master branch, will
be finer-grained control over resource and operation defaults.

Currently, you can set meta-attribute values in the CIB's rsc_defaults
section to apply to all resources, and op_defaults to apply to all
operations. Rules can be used to apply defaults only during certain
times. For example, to set a default stickiness of INFINITY during
business hours and 0 outside those hours:

   <rsc_defaults>
    <meta_attributes id="business-hours" score="2">
      <rule id="business-hours-rule" score="0">
        <date_expression id="business-hours-expr" operation="date_spec">
          <date_spec id="business-hours-spec" hours="9-17" weekdays="1-5"/>
        </date_expression>
      </rule>
      <nvpair id="business-hours-stickiness" name="resource-stickiness" value="INFINITY"/>
    </meta_attributes>
    <meta_attributes id="after-hours" score="1" >
      <nvpair id="after-hours-stickiness" name="resource-stickiness" value="0"/>
    </meta_attributes>
   </rsc_defaults>

But what if you want to change the default stickiness of just pgsql
databases? Or the default timeout of only start operations?

2.0.5 will add new rule expressions for this purpose. Examples:

   <rsc_defaults>
    <meta_attributes id="pgsql-defaults" score="2">
      <rule id="pgsql-defaults-rule" score="0">
        <rsc_expression id="pgsql-defaults-expr" class="ocf" provider="heartbeat" type="pgsqlms"/>
      </rule>
      <nvpair id="pgsql-stickiness" name="resource-stickiness" value="INFINITY"/>
    </meta_attributes>
   </rsc_defaults>

   <op_defaults>
    <meta_attributes id="start-defaults" score="2">
      <rule id="start-defaults-rule" score="0">
        <op_expression id="start-defaults-expr" name="start" interval="0"/>
      </rule>
      <nvpair id="start-timeout" name="timeout" value="60s"/>
    </meta_attributes>
   </op_defaults>

You can combine rsc_expression and op_expression in op_defaults rules,
if for example you want to set a default stop timeout for all
ocf:heartbeat:docker resources.

This obviously can be convenient if you have many resources of the same
type, but it has one other trick up its sleeve: this is the only way
you can affect the meta-attributes of resources implicitly created by
Pacemaker for bundles.

When you configure a bundle, Pacemaker will implicitly create container
resources (ocf:heartbeat:docker, ocf:heartbeat:rkt, or
ocf:heartbeat:podman) and if appropriate, IP resources
(ocf:heartbeat:IPaddr2). Previously, there was no way to directly
affect these resources, but with these new expressions you can at least
configure defaults that apply to them, without having to use those same
defaults for all your resources.
-- 
Ken Gaillot <kgaillot at redhat.com>