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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.

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.

inputs​

Inputs which are provided to the ansible grain will be used in the ansible command line as "extra-vars". The syntax is similar to any grain inputs.

Let's look at an example. In the example we have a blueprint with 2 grains: a VM and an ansible playbook to configure it.

Blueprint:

spec_version: 2
   ...   
grains:
  my_vm:
    kind: terraform
    spec:
      source:
        store: assets
        path:terraform/vcenter/linux_vm
      outputs:
      - vm_ip
      - vm_link
      - vm_name

  configure-vm:
    depends-on: my_vm
    kind: ansible
    spec:
      source:
        store: assets
        path: assets/ansible/configure.yaml
      inputs:
        - nodes: '{{ grains.my_vm.outputs.vm_ip }}'
        - username: '{{ .params.vc_ubuntu_user }}'
        - password: '{{ .params.vc_ubuntu_password }}'
info

Torque supports playbooks which use ansible roles.

Playbook:

- hosts: {{ nodes }}
  tasks:
  - name: configure virtual machine
    azure_rm_virtualmachine:
      username: "{{ username }}"
      password: "{{ password }}"
      …

Torque will create a JSON file containing the grain inputs under the path: /var/run/ansible/inputs/inputs.json.

{
  "nodes": [...],
  "username": ...,
  "password": ...
}

The playbook will be executed with the extra vars in the following way:

ansible-playbook myplaybook.yaml --extra-vars "@/var/run/ansible/inputs/inputs.json"

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 the Ansible 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

Outputs​

Ansible does not support outputs from playbooks natively so Torque adds this support on top of the ansible capabilities. Why would you need outputs from your ansible grain? Output from the ansible grain can be passed to another grain (ansible or not) or to become one of the blueprint outputs so can be provided to the blueprint consumer (the end user).

For this purpose, we have developed the Torque ansible module "export-torque-outputs".

The module accepts a dictionary of output names and values.

Usage example:

Playbook:

tasks:
  - name: task1
      configure_vm:
      …
      register: result1
    …
  - name: task2
      do_something_else:
      …
      register: result2
    

 - name: Export outputs
    torque.collections.export_torque_outputs:
      outputs:
        output1: “{{ result1 }}”
        output2: “{{ result2 }}”
info

The task which runs the "export_torque_outputs" module must be run on localhost.

Blueprint:

grains:
   configure-vm:
      kind: ansible
      spec:
       ...
       outputs:
          - output1
          - output2

If you wish to install the module locally to test it, please run ansible-galaxy collection install torque.collections The module resides in the marketplace : https://galaxy.ansible.com/torque/collections