Red Hat Summit16장. Determining resource location with rules
For more complicated location constraints, you can use Pacemaker rules to determine a resource’s location.
16.1. Pacemaker rules
Pacemaker rules can be used to make your configuration more dynamic. One 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 next depends on the context in which the rule is being used.
| Field | Description |
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Limits the rule to apply only when the resource is in that role. Allowed values: |
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The score to apply if the rule evaluates to |
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The node attribute to look up and use as a score if the rule evaluates to |
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How to combine the result of multiple expression objects. Allowed values: |
16.1.1. Node attribute expressions
Node attribute expressions are used to control a resource based on the attributes defined by a node or nodes. For general information about node attributes, see Configuring node-specific values using node attributes.
| Field | Description |
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| The node attribute to test |
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Determines how the value(s) should be tested. Allowed values: |
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| The comparison to perform. Allowed values:
*
*
*
*
*
*
*
* |
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User supplied value for comparison (required unless |
In addition to any attributes added by the administrator, the cluster defines special, built-in node attributes for each node that can also be used, as described in the following table.
| Name | Description |
|---|---|
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| Node name |
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| Node ID |
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Node type. Possible values are |
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The value of the |
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The value of the |
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| The role the relevant promotable clone has on this node. Valid only within a rule for a location constraint for a promotable clone. |
16.1.2. Time/date based expressions
Date expressions are used to control a resource or cluster option based on the current date/time. They can contain an optional date specification.
| Field | Description |
|---|---|
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| A date/time conforming to the ISO8601 specification. |
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| A date/time conforming to the ISO8601 specification. |
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| Compares the current date/time with the start or the end date or both the start and end date, depending on the context. Allowed values:
*
*
*
* |
16.1.3. Date specifications
Date specifications are used to create cron-like expressions relating to time. Each field can contain a single number or a single range. Instead of defaulting to zero, any field not supplied is ignored.
For example, monthdays="1" matches the first day of every month and hours="09-17" matches the hours between 9 am and 5 pm (inclusive). However, you cannot specify weekdays="1,2" or weekdays="1-2,5-6" since they contain multiple ranges.
| Field | Description |
|---|---|
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| A unique name for the date |
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| Allowed values: 0-59 |
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| Allowed values: 0-59 |
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| Allowed values: 0-23 |
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| Allowed values: 0-31 (depending on month and year) |
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| Allowed values: 1-7 (1=Monday, 7=Sunday) |
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| Allowed values: 1-366 (depending on the year) |
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| Allowed values: 1-12 |
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Allowed values: 1-53 (depending on |
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| Year according the Gregorian calendar |
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May differ from Gregorian years; for example, |
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