Chapter 9. Pacemaker Rules
Chapter 9. Pacemaker Rules Rules can be used to make your configuration more dynamic. One common example is to set one value for resource-stickiness during working hours, to prevent resources from being moved back to their most preferred location, and another on weekends when no one is around to notice an outage. Another use of rules might be to assign machines to different processing groups (using a node attribute) based on time and to then use that attribute when creating location constraints. Each rule can contain a number of expressions, date-expressions and even other rules. The results of the expressions are combined based on the rule's boolean-op field to determine if the rule ultimately evaluates to true or false . What happens depends on the context in which the rule is being used. Table 9.1. Properties of a Rule Field Description role Limits the rule to apply only when the resource is in that role. Allowed values: Started , Slave, and Master . NOTE: A rule with role="Master" cannot determine the initial location of a clone instance. It will only affect which of the active instances will be promoted. score The score to apply if the rule evaluates to true . Limited to use in rules that are part of location constraints. score-attribute The node attribute to look up and use as a score if the rule evaluates to true . Limited to use in rules that are part of location constraints. boolean-op How to combine the result of multiple expression objects. Allowed values: and and or . The default value is and . 9.1. Node Attribute Expressions Node attribute expressions are used to control a resource based on the attributes defined by a node or nodes. Table 9.2. Properties of an Expression Field Description value User supplied value for comparison attribute The node attribute to test type Determines how the value(s) should be tested. Allowed values: string , integer , version operation The comparison to perform. Allowed values: * lt - True if the node attribute's value is less than value * gt - True if the node attribute's value is greater than value * lte - True if the node attribute's value is less than or equal to value * gte - True if the node attribute's value is greater than or equal to value * eq - True if the node attribute's value is equal to value * ne - True if the node attribute's value is not equal to value * defined - True if the node has the named attribute * not_defined - True if the node does not have the named attribute