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10.2.5. Clone Constraints

In most cases, a clone will have a single copy on each active cluster node. If this is not the case, you can indicate which nodes the cluster should preferentially assign copies to with resource location constraints. These constraints are written no differently from those for primitive resources except that the clone’s id is used.

Example 10.5. Some constraints involving clones

    <rsc_location id="clone-prefers-node1" rsc="apache-clone" node="node1" score="500"/>
    <rsc_colocation id="stats-with-clone" rsc="apache-stats" with="apache-clone"/>
    <rsc_order id="start-clone-then-stats" first="apache-clone" then="apache-stats"/>

Ordering constraints behave slightly differently for clones. In the example above, apache-stats will wait until all copies of apache-clone that need to be started have done so before being started itself. Only if no copies can be started will apache-stats be prevented from being active. Additionally, the clone will wait for apache-stats to be stopped before stopping itself.
Colocation of a primitive or group resource with a clone means that the resource can run on any machine with an active copy of the clone. The cluster will choose a copy based on where the clone is running and the resource’s own location preferences.
Colocation between clones is also possible. If one clone A is colocated with another clone B, the set of allowed locations for A is limited to nodes on which B is (or will be) active. Placement is then performed normally.