How to define a service catalog using an ansible playbook

In the previous example, we used a python script to implement a software catalog. In this example, we use Ansible to create Apache server.

Figure 1. Apache example

1. Steps

Step 1. Import TOSCA types

imports:
  - tosca-normative-types:1.0.0-ALIEN20

Step 2. Implement the interfaces

Implement the node Apache with the create interfaces and provide an Ansible playbook for the interface (e.g., apache-create.yaml):

node_types:
  myservice.nodes.SoftwareComponent.Apache:
    derived_from: tosca.nodes.SoftwareComponent
    ...
    interfaces:
      Standard:
        create:
          inputs:
            # HOST is the keyword to get more information about the hosted compute node at runtime
            APACHE_LISTEN_IP: { get_attribute: [HOST, private_address] }
          # ansible script
          implementation: playbooks/apache-create.yaml

Note

• Use the keyword HOST to get information of the hosted compute node.

• Use the function get_attribute to get the runtime attribute private_address of the hosted compute node. The compute node also has the following attributes available at runtime that you can use by default: private_address, public_address:

Figure 2. Runtime attributes of a compute node

Step 3. Implement an ansible playbook for the interface

Write the Ansible playbook (e.g., apache-create.yaml) to install Apache. In this example, we import a third party ansible role geerlingguy.apache to install Apache:

# playbooks/apache-create.yaml
- name: Install Apache
  # "hosts" must be set to all. Otherwise the deployment will fail.
  hosts: all
  tasks:
    - name: Install Apache
      become: true
      import_role:
        name: geerlingguy.apache
      vars:
        # The environment variable APACHE_LISTEN_IP is the input parameter of the create interface.
        apache_listen_ip: "{{ APACHE_LISTEN_IP }}"
        ...

In the same folder of the Ansible playbook, we have an Ansible role available at playbooks/roles/geerlingguy.apache

Figure 3. Playbook directory

Expected result

The orchestration engine will apply the ansible playbook apache-create.yaml on the remote compute node, which in turn uses the Ansible role geerlingguy.apache to create Apache.

2. Known limitations

2.1. Output a comma character

• The output is a string but cannot contain a comma character ,. For a workaround, use encode:

set_fact:
  # ca.cert may contain a comma, so we encode it
  CA_CERT: "{{ lookup('file', '/tmp/ca.cert') | b64encode }}"

2.2. Output with become true

• The orchestrator cannot read the output if set_fact is used together with become: true:

- name: my tasks
  hosts: all
  # cannot get output
  become: true
  tasks:
    - name: Set an output
      set_fact:
        OUTPUT: "A result of my tasks"

• For a workaround, use become: true in a task where you need it:

- name: my tasks
  hosts: all
  tasks:
    - name: A task with become true
      become: true

    - name: Set an output without become true
      set_fact:
        OUTPUT: "A result of my tasks"

3. Links

• See full example how to use ansible script

last updated: 2025-01-30 16:08 UTC - commit: 7a893a743a3e51d50f0a66d2fd8961e4c6b299e3