How to define a software component using an 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 TOSCA types

- tosca-normative-types:1.0.0-ALIEN20

Step 2. Implement the interfaces

We implement the create interfaces by providing an ansible script (e.g., mongodb_install.yaml):

derived_from: tosca.nodes.SoftwareComponent
# 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
  • 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:

Runtime attributes of a compute node

Step 3a. Implement an ansible playbook for the interface

In the following example, the ansible script (e.g., mongodb_install.yaml) imports a third party ansible role undergreen.ansible-role-mongodb and uses it to install mongodb:

# playbooks/mongodb_install.yaml
- name: Install MongoDB
# "hosts" must be set to all. Otherwise the deployment will fail.
hosts: all
strategy: free
become: true
become_method: sudo
- name: Install MongoDB using a 3rd party role
name: undergreen.ansible-role-mongodb
# The environment variables IP_ADDRESS and MONGODB_PORT are the
# input parameters of the create interface.
mongodb_net_bindip: "{{ IP_ADDRESS }}"
mongodb_net_port: "{{ MONGODB_PORT }}"

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

The orchestration engine will apply the ansible playbook mongodb_install.yaml on the remote compute node, which in turn imports the ansible role undergreen.ansible-role-mongodb to create the mongodb.

Step 3b. (alternative) Zip the whole playbook folder

Define ansible roles

  • In this scenario, we create a folder (e.g., playbook) contaning more than one roles (e.g., create, configure, delete, start, and stop).
  • Each roles has an entry script (e.g., the entry script create.yml imports the role create).

Zip the playbook folder

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

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

Implement the interface

In the create interfaces, we specify the zip file as an implementation and set the PLAYBOOK_ENTRY to the entry script create.yml:

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

Expected result

The orchestration engine will apply the entry script create.yml, which in turn imports the role create (in the zip file) to create the component on the remote compute node.

Full example