The Ansible Grain

The Ansible grain is Torque’s native support for orchestrating the execution of Ansible playbooks as part of a Torque blueprint. The referenced playbook can rely on vars or inventory-hosts that are dynamically provided by Torque, and then utilize them to perform configuration management, updates, a health check or any other flow that is executable from Ansible.

Note: an Ansible grain does not provide grain outputs.

Tools and technologies

The following tools and technologies are installed out of the box on our agents in the Kubernetes pods and can be used when writing grain scripts (pre/post, etc.):

• dotnet
• git
• python3
• pip3
• ansible
• openssh-client

source

The source section of an Ansible grain provides Torque with the information on where the Ansible playbook is stored and should be retrieved from. This could be either a direct source URL to an Ansible playbook YAML file, or it can be a reference from a Torque-connected git repository.

Example - direct:

My_Ansible_Grain:
  depends-on: Ubuntu_VM
  kind: ansible
  spec:
    source:
      path: https://github.com/MyOrg/my-repo//ansible/install_httpd_rhel.yaml

Example - repository:

My_Ansible_Grain:
  kind: ansible
  spec:
    source:
      store: assets
      path: assets/ansible/install_apache2_webgame_ubuntu.yaml

agent

Please see the grain agent for more details.

Inventory-file

Inventory file is a special grain section unique to the ansible grain, that allows you to provide in a YAML structured format, the content of the Ansible inventory file that will be generated for the Ansible playbook to use. For a deep understanding of the format of this file, please see Ansible’s official documentation at https://docs.ansible.com/ansible/latest/inventory_guide/intro_inventory.html#inventory-basics-formats-hosts-and-groups. The general standard structure for such a file is as follows:

host_group:
  hosts:
    host1:
      host1_var: host1_var_value
    host2:
      host2_var: host1_var_value
  vars:
    group_var: group_var_value

Depending on the Ansible packages used in the playbook, these host and group variables may be used automatically by the package step (in which case, they must be provided in a specific name, for example an “ansible_become: yes/no” group var will determine if the actions in the playbook need to be run as a different user from the host connection info.). Variables not defined on a host will automatically default to the values set in the vars section of the host_group. For example, the below playbook:

---
- gather_facts: no
  hosts: all
  tasks:
  - name: Print Hello World
    debug: 
      msg: "Hello World, my name is {{ person_name}}"

with the below inventory file:

      inventory-file:
        all:
          hosts:
            host1:
              person_name: John
            host2:          
          vars:
            person_name: Doe

will result in this output

TASK [Print Hello World] *******************************************************
ok: [host1] => {
    "msg": "Hello World, my name is John"
}
ok: [host2] => {
    "msg": "Hello World, my name is Doe"
}

Any section of the “inventory-file:” can contain dynamic values from dependent grains, from the blueprint’s inputs or from Torque’s parameter storage. For more information, see Torque Templating engine. Example: Below is an example of a grains section of a blueprint, containing an Ansible grain:

 grains:
  hello_world_ansible:
    kind: ansible
    spec:
      source:
        store: assets
        path: ansible/hello_world.yaml
      agent:
        name: my-torque-agent
      inventory-file:
        all:
          hosts:
            host1:
              person_name: John
            host2:          
          vars:
            person_name: Doe