DSC Resource kind schema reference

Article
06/24/2024

Synopsis

Identifies whether a resource is an adapter resource, a group resource, or a normal resource.

Metadata

SchemaDialect: https://json-schema.org/draft/2020-12/schema
SchemaID:      https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/definitions/resourceKind.json
Type:          string
ValidValues:  [Resource, Adapter, Group, Import]

Description

DSC supports three kinds of command-based DSC Resources:

Resource - Indicates that the manifest isn't for a group or adapter resource.
Group - Indicates that the manifest is for a group resource.
Adapter - Indicates that the manifest is for an adapter resource.
Import - Indicates that the manifest is for an importer resource.

When kind isn't defined in the resource manifest, DSC infers the value for the property. If the adapter property is defined in the resource manifest, DSC infers the value of kind as Adapter. If the adapter property isn't defined, DSC infers the value of kind as Resource. DSC can't infer whether a manifest is for a group resource.

When defining a group resource, always explicitly define the kind property in the manifest as Group.

Adapter resources

An adapter resource makes non-command-based resources available to DSC. They always have a resources property that takes an array of nested resource instances. Adapters may provide additional control over how the adapted resources are processed.

An adapter resource must always define the adapter and validate properties in the resource manifest.

For example, the Microsoft.DSC/PowerShell adapter enables you to use PowerShell Desired State Configuration (PSDSC) resources in DSC. PSDSC resources are published as components of PowerShell modules. They don't define resource manifests.

Group resources

Group resources always operate on nested DSC Resource instances. Group resources can change how the nested instances are processed, like the Microsoft.DSC/Assertion group resource.

A group resource must always define the kind property in the resource manifest.

Group resources can also be used to bundle sets of resources together for processing, like the Microsoft.DSC/Group resource. You can use the dependsOn property for a resource instance in a configuration to point to a group resource instead of enumerating each resource in the list.

Importer resources

Importer resources resolve an external source to a set of nested DSC Resource instances. The properties of an importer resource define how to find and resolve the external source.

An importer resource must always define the kind and resolve properties in the resource manifest.

For example, the Microsoft.DSC/Import importer resource resolves instances from an external configuration document, enabling you to compose configurations from multiple files.

Nested resource instances

The resource instances declared in adapter and group resources or resolved by importer resources are called nested resource instances.

For nested instances, a resource instance is adjacent if:

It's declared in the same group or adapter instance.
It's resolved by the same importer instance.

A resource instance is external to a nested instance if:

It's declared outside of the group or adapter instance
It's resolved by a different importer instance
It's nested inside an adjacent group, adapter, or importer instance.

For top-level instances, other instances at the top-level are adjacent. All other instances are external.

Consider the following configuration snippet. It defines seven resource instances:

At the top-level, the configuration defines the TopLevelEcho, TopLevelOSInfo, and TopLevelGroup instances.
The TopLevelGroup instance defines the nested instances NestedEcho and NestedGroup.
The NestedGroup instance defines the nested instances DeeplyNestedEcho and DeeplyNestedOSInfo.

resources:
- name: TopLevelEcho
  type: Test/Echo
  properties: { output: 'top level instance' }
- name: TopLevelOSInfo
  type: Microsoft/OSInfo
  properties: { }
- name: TopLevelGroup
  type: Microsoft.DSC/Group
  properties:
    $schema:
    resources:
    - name: NestedEcho
      type: Test/Echo
      properties: { output: 'nested instance' }
    - name: NestedGroup
      type: Microsoft.DSC/Group
      properties:
        $schema:
        resources:
        - name: DeeplyNestedEcho
          type: Test/Echo
          properties: { output: 'deeply nested instance' }
        - name: DeeplyNestedOSInfo
          type: Microsoft/OSInfo
          properties: { }

The following matrix defines the relations of each instance in the configuration:

	TopLevelEcho	TopLevelOSInfo	TopLevelGroup	NestedEcho	NestedGroup	DeeplyNestedEcho	DeeplyNestedOSInfo
TopLevelEcho	Self	Adjacent	Adjacent	External	External	External	External
TopLevelOSInfo	Adjacent	Self	Adjacent	External	External	External	External
TopLevelGroup	Adjacent	Adjacent	Self	External	External	External	External
NestedEcho	External	External	External	Self	Adjacent	External	External
NestedGroup	External	External	External	Adjacent	Self	External	External
DeeplyNestedEcho	External	External	External	External	External	Self	Adjacent
DeeplyNestedOSInfo	External	External	External	External	External	Adjacent	Self

Referencing nested instances

Nested resource instances have limitations for the dependsOn property and the reference() configuration function.

You can only reference adjacent instances. You can't reference a nested instance from outside of the instance that declares or resolves it. You can't use a reference to a resource outside of the group, adapter, or importer resource for a nested instance.
You can only use the dependsOn property for adjacent instances. You must add a dependency on the group, adapter, or importer instance, not a nested instance. Nested instances can't depend on external instances.

The following examples show valid and invalid references and dependencies. The examples use the Microsoft.DSC/Group resource, but the functionality is the same for adapter and import resources.

Example 1 - Valid references and dependencies

This example configuration defines several valid references and dependencies. It also defines two instances of the Microsoft.DSC/Group resource, one nested inside the other.

The top level instance of the Test/Echo resource references and depends on the top-level instance of the Microsoft/OSInfo resource. The top-level instances of the Test/Echo and Microsoft/OSInfo resources both depend on the top-level instance of the Microsoft.DSC/Group resource.

resources:
# The top level echo references and depends on the top-level OSInfo.
# It also depends on the top-level Group.
- name: Top level echo
  type: Test/Echo
  properties:
    output:  >-
      [reference(
        resourceId('Microsoft/OSInfo', 'Top level OSInfo')
      ).actualState]
  dependsOn:
    - "[resourceId('Microsoft/OSInfo', 'Top level OSInfo')]"
    - "[resourceId('Microsoft.DSC/Group', 'Top level group')]"
# The top level OSInfo depends on the top-level Group.
- name: Top level OSInfo
  type: Microsoft/OSInfo
  properties: {}
  dependsOn:
    - "[resourceId('Microsoft.DSC/Group', 'Top level group')]"
- name: Top level group
  type: Microsoft.DSC/Group
  properties: # snipped for brevity

The top-level instance of Microsoft.DSC/Group defines three nested resource instances: Test/Echo, Microsoft/OSInfo, and Microsoft.DSC/Group. As at the top-level, the Test/Echo instance references and depends on the adjacent nestedMicrosoft/OSInfo instance and that instance depends on the adjacent nested Microsoft.DSC/Group instance.

# Other top-level instances snipped for brevity
- name: Top level group
  type: Microsoft.DSC/Group
  properties:
    $schema: https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/config/document.json
    resources:
    # The nested echo references and depends on the adjacent nested OSInfo.
    - name: Nested echo
      type: Test/Echo
      properties:
        output:  >-
          [reference(
            resourceId('Microsoft/OSInfo', 'Nested OSInfo')
          ).actualState]
      dependsOn:
        - "[resourceId('Microsoft/OSInfo', 'Nested OSInfo')]"
    # The nested OSInfo depends on the adjacent nested Group.
    - name: Nested OSInfo
      type: Microsoft/OSInfo
      properties: {}
    - name: Nested Group
      type: Microsoft.DSC/Group
      properties: # snipped for brevity

Finally, the nested instance of Microsoft.DSC/Group defines two nested instances. The deeply nested instance of Test/Echo references and depends on the deeply nested instance of Microsoft/OSInfo.

- name: Top level group
  type: Microsoft.DSC/Group
  properties:
    $schema: https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/config/document.json
    resources:
    # Snipped the Test/Echo and Microsoft/OSInfo instances for brevity
    - name: Nested Group
      type: Microsoft.DSC/Group
      properties:
        $schema: https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/config/document.json
        resources:
        # The deeply nested echo references and depends on the adjacent
        # deeply nested OSInfo.
        - name: Deeply nested echo
          type: Test/Echo
          properties:
            output:  >-
              [reference(
                resourceId('Microsoft/OSInfo', 'Deeply nested OSInfo')
              ).actualState]
          dependsOn:
            - "[resourceId('Microsoft/OSInfo', 'Deeply nested OSInfo')]"
        - name: Deeply nested OSInfo
          type: Microsoft.OSInfo
          properties: {}

In every case, the references and dependencies are to adjacent instances in the configuration. Instances at the top level only depend on or reference other instances at the top level. Instances nested in the top-level group only depend on or reference other nested instances in the same group. The deeply nested instances defined in the nested group only depend on or reference other deeply nested instances in the same group.

Putting the configuration together, you get this full document:

# yaml-language-server: $schema=https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/bundled/resource/manifest.vscode.json
$schema: https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/config/document.json
resources:
# The top level echo references and depends on the top-level OSInfo.
- name: Top level echo
  type: Test/Echo
  properties:
    output:  >-
      [reference(
        resourceId('Microsoft/OSInfo', 'Top level OSInfo')
      ).actualState]
  dependsOn:
    - "[resourceId('Microsoft/OSInfo', 'Top level OSInfo')]"
# The top level OSInfo depends on the top-level Group.
- name: Top level OSInfo
  type: Microsoft/OSInfo
  properties: {}
  dependsOn:
    - "[resourceId('Microsoft.DSC/Group', 'Top level group')]"
- name: Top level group
  type: Microsoft.DSC/Group
  properties:
    $schema: https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/config/document.json
    resources:
    # The nested echo references and depends on the adjacent nested OSInfo.
    - name: Nested echo
      type: Test/Echo
      properties:
        output:  >-
          [reference(
            resourceId('Microsoft/OSInfo', 'Nested OSInfo')
          ).actualState]
      dependsOn:
        - "[resourceId('Microsoft/OSInfo', 'Nested OSInfo')]"
    # The nested OSInfo depends on the adjacent nested Group.
    - name: Nested OSInfo
      type: Microsoft/OSInfo
      properties: {}
    - name: Nested Group
      type: Microsoft.DSC/Group
      properties:
        $schema: https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/config/document.json
        resources:
        # The deeply nested echo references and depends on the adjacent
        # deeply nested OSInfo.
        - name: Deeply nested echo
          type: Test/Echo
          properties:
            output:  >-
              [reference(
                resourceId('Microsoft/OSInfo', 'Deeply nested OSInfo')
              ).actualState]
          dependsOn:
            - "[resourceId('Microsoft/OSInfo', 'Deeply nested OSInfo')]"
        - name: Deeply nested OSInfo
          type: Microsoft.OSInfo
          properties: {}

Example 2 - Invalid reference and dependency on a nested instance

This example configuration is invalid, because the top-level instance of the Test/Echo resource references and depends on the nested Microsoft/OSInfo instance. The nested instance is external to the top-level instance, not adjacent.

# yaml-language-server: $schema=https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/bundled/resource/manifest.vscode.json
$schema: https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/config/document.json
resources:
- name: Top level echo
  type: Test/Echo
  properties:
    output:  >-
      [reference(
        resourceId('Microsoft/OSInfo', 'Nested OSInfo')
      ).actualState]
  dependsOn:
    - "[resourceId('Microsoft/OSInfo', 'Nested OSInfo')]"
- name: Top level group
  type: Microsoft.DSC/Group
  properties:
    $schema: https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/config/document.json
    resources:
    - name: Nested OSInfo
      type: Microsoft/OSInfo
      properties: {}

Example 3 - Invalid reference and dependency on an external instance

This example configuration is invalid, because the nested instance of the Test/Echo resource references and depends on the top-level Microsoft/OSInfo instance. The top-level instance is external to the nested instance, not adjacent.

# yaml-language-server: $schema=https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/bundled/resource/manifest.vscode.json
$schema: https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/config/document.json
resources:
- name: Top level OSInfo
  type: Microsoft/OSInfo
  properties: {}
- name: Top level group
  type: Microsoft.DSC/Group
  properties:
    $schema: https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/config/document.json
    resources:
    - name: Nested echo
      type: Test/Echo
      properties:
        output:  >-
          [reference(
            resourceId('Microsoft/OSInfo', 'Top level OSInfo')
          ).actualState]
      dependsOn:
        - "[resourceId('Microsoft/OSInfo', 'Top level OSInfo')]"

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