⁠Chapter 8. Rules

Table of Contents

Rules can be used to make your configuration more dynamic, allowing values to change depending on the time or the value of a node attribute. Examples of things rules are useful for:

Set a higher value for resource-stickiness during working hours, to minimize downtime, and a lower value on weekends, to allow resources to move to their most preferred locations when people aren’t around to notice.
Automatically place the cluster into maintenance mode during a scheduled maintenance window.
Assign certain nodes and resources to a particular department via custom node attributes and meta-attributes, and add a single location constraint that restricts the department’s resources to run only on those nodes.

Each constraint type or property set that supports rules may contain one or more rule elements specifying conditions under which the constraint or properties take effect. Examples later in this section will make this clearer.

⁠8.1. Rule Properties

⁠

Table 8.1. Attributes of a rule Element

Attribute	Default	Description
`id`		A unique name for the rule (required)
`role`	`Started`	The rule is in effect only when the resource is in the specified role. Allowed values are `Started`, `Slave`, and `Master`. A rule with `role="Master"` cannot determine the initial location of a clone instance and will only affect which of the active instances will be promoted.
`score`		If this rule is used in a location constraint and evaluates to true, apply this score to the constraint. Only one of `score` and `score-attribute` may be used.
`score-attribute`		If this rule is used in a location constraint and evaluates to true, use the value of this node attribute as the score to apply to the constraint. Only one of `score` and `score-attribute` may be used.
`boolean-op`	`and`	If this rule contains more than one condition, a value of `and` specifies that the rule evaluates to true only if all conditions are true, and a value of `or` specifies that the rule evaluates to true if any condition is true.

A rule element must contain one or more conditions. A condition may be an expression element, a date_expression element, or another rule element.