Ansible Operator Watches

The Watches file contains a list of mappings from custom resources, identified by it’s Group, Version, and Kind, to an Ansible Role or Playbook. The Operator expects this mapping file in a predefined location: /opt/ansible/watches.yaml These resources, as well as child resources (determined by owner references) will be monitored for updates and cached.

• group: The group of the Custom Resource that you will be watching.
• version: The version of the Custom Resource that you will be watching.
• kind: The kind of the Custom Resource that you will be watching.
• role (default): Specifies a role to be executed. This field is mutually exclusive with the “playbook” field. This field can be:
  • an absolute path to a role directory.
  • a relative path within one of the directories specified by ANSIBLE_ROLES_PATH environment variable or ansible-roles-path flag.
  • a relative path within the current working directory, which defaults to /opt/ansible/roles.
  • a fully qualified collection name of an installed Ansible collection. Ansible collections are installed to ~/.ansible/collections or /usr/share/ansible/collections by default. If they are installed elsewhere, use the ANSIBLE_COLLECTIONS_PATH environment variable or the ansible-collections-path flag
• playbook: This is the playbook name that you have added to the container. This playbook is expected to be simply a way to call roles. This field is mutually exclusive with the “role” field. When running locally, the playbook is expected to be in the current project directory.
• vars: This is an arbitrary map of key-value pairs. The contents will be passed as extra_vars to the playbook or role specified for this watch.
• reconcilePeriod (optional): The maximum interval in seconds that the operator will wait before beginning another reconcile, even if no watched events are received. When an operator watches many resources, each reconcile can become expensive, and a low value here can actually reduce performance. Typically, this option should only be used in advanced use cases where watchDependentResources is set to False and when is not possible to use the watch feature. E.g To managing external resources that don’t raise Kubernetes events.
• manageStatus (optional): When true (default), the operator will manage the status of the CR generically. Set to false, the status of the CR is managed elsewhere, by the specified role/playbook or in a separate controller.
• blacklist: A list of child resources (by GVK) that will not be watched or cached.

An example Watches file:

---
# Simple example mapping Foo to the Foo role
- version: v1alpha1
  group: foo.example.com
  kind: Foo
  role: Foo
# Simple example mapping Bar to a playbook
- version: v1alpha1
  group: bar.example.com
  kind: Bar
  playbook: playbook.yml
# More complex example for our Baz kind
# Here we will disable requeuing and be managing the CR status in the playbook,
# and specify additional variables.
- version: v1alpha1
  group: baz.example.com
  kind: Baz
  playbook: baz.yml
  reconcilePeriod: 0
  manageStatus: False
  vars:
    foo: bar
# ConfigMaps owned by a Memcached CR will not be watched or cached.
- version: v1alpha1
  group: cache.example.com
  kind: Memcached
  role: /opt/ansible/roles/memcached
  blacklist:
    - group: ""
      version: v1
      kind: ConfigMap
# Example usage with a role from an installed Ansible collection
- version: v1alpha1
  group: bar.example.com
  kind: Bar
  role: myNamespace.myCollection.myRole
# Example filtering of resources with specific labels
- version: v1alpha1
  group: bar.example.com
  kind: Bar
  playbook: playbook.yml
  selector:
    matchLabels:
      foo: bar
    matchExpressions:
      - {key: foo, operator: In, values: [bar]}
      - {key: baz, operator: Exists, values: []}

The advanced features can be enabled by adding them to your watches file per GVK. They can go below the group, version, kind and playbook or role.

Some features can be overridden per resource via an annotation on that CR. The options that are overridable will have the annotation specified below.

Example

---
- version: v1alpha1
  group: app.example.com
  kind: AppService
  playbook: playbook.yml
  maxRunnerArtifacts: 30
  reconcilePeriod: 5s
  manageStatus: False
  watchDependentResources: False
  snakeCaseParameters: False
  finalizer:
    name: app.example.com/finalizer
    vars:
      state: absent

Note: By using the command operator-sdk add api you are able to add additional CRDs to the project API, which can aid in designing your solution using concepts such as encapsulation, single responsibility principle, and cohesion, which could make the project easier to read, debug, and maintain. With this approach, you are able to customize and optimize the configurations more specifically per GVK via the watches.yaml file.

Example:

---
- version: v1alpha1
  group: app.example.com
  kind: AppService
  playbook: playbook.yml
  maxRunnerArtifacts: 30
  reconcilePeriod: 5s
  manageStatus: False
  watchDependentResources: False
  finalizer:
    name: app.example.com/finalizer
    vars:
      state: absent
- version: v1alpha1
  group: app.example.com
  kind: Database
  playbook: playbook.yml
  watchDependentResources: True
  manageStatus: True

Last modified February 3, 2021: *: format finalizers correctly (ee7e682a)