8.2. Node Attribute Expressions

Expression objects are used to control a resource based on the attributes defined by a node or nodes.

Table 8.2. Properties of an Expression

Field	Default	Description
`id`		A unique name for the expression (required)
`attribute`		The node attribute to test (required)
`type`	`string`	Determines how the value(s) should be tested. Allowed values are `string`, `integer`, and `version`.
`operation`		The comparison to perform (required). Allowed values: `lt:` True if the value of the node’s `attribute` is less than `value` `gt:` True if the value of the node’s `attribute` is greater than `value` `lte:` True if the value of the node’s `attribute` is less than or equal to `value` `gte:` True if the value of the node’s `attribute` is greater than or equal to `value` `eq:` True if the value of the node’s `attribute` is equal to `value` `ne:` True if the value of the node’s `attribute` 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
`value`		User-supplied value for comparison (required)
`value-source`	`literal`	How the `value` is derived (since 1.1.17). Allowed values: `literal`: `value` is a literal string to compare against `param`: `value` is the name of a resource parameter to compare against (only valid in location constraints) `meta`: `value` is the name of a resource meta-attribute to compare against (only valid in location constraints)

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.

Table 8.3. Built-in node attributes

Name	Value
`#uname`	Node name
`#id`	Node ID
`#kind`	Node type. Possible values are `cluster`, `remote`, and `container`. Kind is `remote` for Pacemaker Remote nodes created with the `ocf:pacemaker:remote` resource, and `container` for Pacemaker Remote guest nodes and bundle nodes (since 1.1.13)
`#is_dc`	"true" if this node is a Designated Controller (DC), "false" otherwise
`#cluster-name`	The value of the `cluster-name` cluster property, if set
`#site-name`	The value of the `site-name` cluster property, if set, otherwise identical to `#cluster-name`
`#role`	The role the relevant multistate resource has on this node. Valid only within a rule for a location constraint for a multistate resource.