Basic_Ansible.md

2. Create a software component using ansible playbook

In the previous example, we used a python script to implement a software component. In this example, we use an ansible playbook to create a mongodb.

Step 1. Import yorc-types

imports:
  - tosca-normative-types:1.0.0-ALIEN20
  - yorc-types:1.1.0

Step2. Implement the interfaces

In the interfaces, we can use an ansible script mongodb_install.yaml as follows:

node_types:
  otc.nodes.SoftwareComponent.MongoDB:
    derived_from: org.ystia.nodes.SoftwareComponent
    ...
    interfaces:
      Standard:
        create:
          inputs:
            # HOST is the keyword to get more information about the hosted compute node at runtime
            IP_ADDRESS: { get_attribute: [HOST, private_address] }
            MONGODB_PORT: { get_property: [SELF, port] }
          # ansible script
          implementation: playbooks/mongodb_install.yaml

Notice:

• We use the HOST keyword to get information of the compute node, on which the mongodb node is hosted.
• The compute node has the following attributes to use by default: private_address, public_address (Figure 1).
• We use get_attribute to get the attribute private_address of the hosted compute node at runtime.

Figure 1: Attributes of a compute node.

In the same folder of the node definition, we have an ansible role available at playbooks/roles/undergreen.ansible-role-mongodb

Figure 2: Ansible role

The ansible script mongodb_install.yaml imports the ansible role undergreen.ansible-role-mongodb and uses it to install a mongodb as follows:

# playbooks/mongodb_install.yaml
- name: Install MongoDB
  hosts: all
  strategy: free
  become: true
  become_method: sudo
  tasks:
    - name: Install MongoDB using a 3rd party role
      import_role:
        name: undergreen.ansible-role-mongodb
      vars:
        mongodb_net_bindip: "{{ IP_ADDRESS }}"
        mongodb_net_port: "{{ MONGODB_PORT }}"
        ...

Here, the environment variables IP_ADDRESS and MONGODB_PORT are the inputs parameters of the create interface.

Step 2. (alternative) Zip the whole playbook folder

2.1. We have a playbook folder contaning the roles folder and several entry scripts (e.g., create.yml, start.yml, etc.) for each role.

Figure 2: The entry script create.yml for role create

2.2. Zip the content of the playbook folder into the file playbook/playbook.ansible

cd playbook && rm -f playbook.ansible && zip -r playbook.ansible *

2.3. Use the zip file in the interfaces and set the PLAYBOOK_ENTRY to the entry script create.yml:

    interfaces:
      Standard:
        create:
          inputs:
            # the entry script in the playbook folder
            PLAYBOOK_ENTRY: create.yml
          # the zip file of the playbook folder content
          implementation: playbook/playbook.ansible

Then the role create in the zip file will be used to create our node.

Where to go from here?

• See full example how to use ansible script
• See full example how to use playbook as a zip file
• Next: How to define a ConnectsTo relationship between two software components?