Resource collectors
Resource collectors select a group of resources by searching the attributes of each resource in the catalog, even resources which haven’t yet been declared at the time the collector is written. Collectors realize virtual resources, are used in chaining statements, and override resource attributes. Collectors have an irregular syntax that enables them to function as a statement and a value.
Syntax
User <| title == 'luke' |> # Will collect a single user resource whose title is 'luke'
User <| groups == 'admin' |> # Will collect any user resource whose list of supplemental groups includes 'admin'
Yumrepo['custom_packages'] -> Package <| tag == 'custom' |> # Will create an order relationship with several package resources
The
general form of a resource collector is: -
A capitalized resource type name. This cannot be
Class
, and there is no way to collect classes. -
<|
- An opening angle bracket (less-than sign) and pipe character. -
Optionally, a search expression.
-
|>
- A pipe character and closing angle bracket (greater-than sign)
Using a special expression syntax, collectors search the values of resource titles and attributes. This resembles the normal syntax for Puppet expressions, but is not the same.
Package <| provider == yum |>
collects
only packages whose provider
attribute is explicitly
set to yum
in the manifests. It does not match packages that would
default to the yum
provider based on the state of the target system.and
and or
operators. You can create complex expressions using four operators.
-
==
(equality search) - This operator is non-symmetric:
-
The left operand (attribute) must be the name of a resource attribute or the word title (which searches on the resource’s title).
-
The right operand (search key) must be a string, boolean, number, resource reference, or undef. The behavior of arrays and hashes in the right operand is undefined in this version of Puppet.
-
-
!=
(non-equality search) - This operator is non-symmetric:
-
The left operand (attribute) must be the name of a resource attribute or the word title (which searches on the resource’s title).
-
The right operand (search key) must be a string, boolean, number, resource reference, or undef. The behavior of arrays and hashes in the right operand is undefined in this version of Puppet.
-
-
and
- Both operands must be valid search expressions. For
a given resource, this operator matches if both of
the operands match for that resource. This operator has higher priority
than
or
. -
or
- Both operands must be valid search expressions. For
a given resource, this operator matches if either of
the operands match for that resource. This operator has lower priority
than
and
.
Location
Use resource collectors in a collector attribute block for amending resource attributes, or as the operand of a chaining statement, or as independent statements.
-
As the value of a resource attribute
-
As the argument of a function
-
Within an array or hash
-
As the operand of an expression other than a chaining statement
Behavior
A resource collector will realize any virtual resources matching its search expression. Empty search expressions match every resource of the specified resource type.
-
In a chaining statement, a collector acts as a proxy for every resource (virtual or not) that matches its search expression.
-
When given a block of attributes and values, a collector sets and overrides those attributes for every resource (virtual or not) matching its search expression.
Exported resource collectors
An exported resource collector uses a modified syntax that realizes exported resources and imports resources published by other nodes.
To use exported resource collectors, enable catalog storage and
searching (storeconfigs
). See Exported
resources for more details. To enable exported resources, follow
the installation instructions and
Puppet configuration
instructions in the PuppetDB docs.
Like normal collectors, use exported resource collectors with attribute blocks and chaining statements.
Nagios_service <<| |>> # realize all exported nagios_service resources
The
general form of an exported resource collector is: -
The resource type name, capitalized.
-
<<|
— Two opening angle brackets (less-than signs) and a pipe character. -
Optionally, a search expression.
-
|>>
— A pipe character and two closing angle brackets (greater-than signs).