9.4. Reusing Rules, Options and Sets of Operations

Sometimes a number of constraints need to use the same set of rules and resources need to set the same options an parameters. To simplify this situation, you can refer to an existing object using an id-ref instead of an id.

So if for one resource you have


  <rsc_location id="WebServer-connectivity" rsc="Webserver">
   <rule id="ping-prefer-rule" score-attribute="pingd" >
    <expression id="ping-prefer" attribute="pingd" operation="defined"/>
   </rule>
  </rsc_location>

Then instead of duplicating the rule for all your other resources, you can instead specify

Example 9.7. Referencing rules from other constraints


  <rsc_location id="WebDB-connectivity" rsc="WebDB">
      <rule id-ref="ping-prefer-rule"/>
  </rsc_location>

Important

The cluster will insist that the rule exists somewhere. Attempting to add a reference to a non-existing rule will cause a validation failure, as will attempting to remove a rule that is referenced elsewhere.

The same principle applies for meta_attributes and instance_attributes as illustrated in the example below

Example 9.8. Referencing attributes, options and operations from other resources


  <primitive id="mySpecialRsc" class="ocf" type="Special" provider="me">
   <instance_attributes id="mySpecialRsc-attrs" score="1" >
    <nvpair id="default-interface" name="interface" value="eth0"/>
    <nvpair id="default-port" name="port" value="9999"/>
   </instance_attributes>
   <meta_attributes id="mySpecialRsc-options">
    <nvpair id="failure-timeout" name="failure-timeout" value="5m"/>
    <nvpair id="migration-threshold" name="migration-threshold" value="1"/>
    <nvpair id="stickiness" name="resource-stickiness" value="0"/>
   </meta_attributes>
   <operations id="health-checks">
     <op id="health-check" name="monitor" interval="60s"/>
     <op id="health-check" name="monitor" interval="30min"/>
    </operations>
  </primitive>
  <primitive id="myOtherlRsc" class="ocf" type="Other" provider="me">
   <instance_attributes id-ref="mySpecialRsc-attrs"/>
   <meta_attributes id-ref="mySpecialRsc-options"/>
   <operations id-ref="health-checks"/>
  </primitive>