Lab 009 - Roles¶

01. What are Ansible roles?¶

Roles let you automatically load related vars, files, tasks, handlers, and other Ansible artifacts based on a known file structure.
After you group your content into roles, you can easily reuse them and share them with other users.
By default, Ansible will look in each directory within a role for the file names main/main.yml/main.yaml.

02. Ansible roles file structure¶

Files	Description
tasks	the main list of tasks that the role executes
handlers	handlers, which may be used within or outside this role
library	modules, which may be used within this role (see Embedding modules and plugins in roles for more information)
defaults	default variables for the role (see Using Variables for more information) these variables have the lowest priority of any variables available and can be easily overridden by any other variable, including `inventory variables`
vars	other variables for the role (see Using Variables for more information)
files	files that the role deploys
templates	templates that the role deploys
meta	metadata for the role, including role dependencies and optional Galaxy metadata, such as supported platforms

03. Building an Ansible role¶

In this demo we will create a role for deploying a nodeJS app.
The app will be deployed from a pre-defined code.
Each server will be deployed with its own configuration (values).
We will also deploy some other files for learning purposes.

04. Initialize file structure¶

# Lets create the roles file structure
ansible-galaxy init codewizard_lab_role

- The file system of the role will look like:

05. Create the role content¶

Create the defaults/main.yml¶

---
### defaults/main.yml
###
### This file contains the variables for the Demo lab
###

# Defaults file for codewizard_lab_role
motd_message: "Welcome to Ansible Roles Lab"

### The packages we wish to install on the servers
apt_packages:
  - python3
  - nodejs
  - npm

# Packages to verify that they were installed
apt_packages_verify:
  - python3
  - npm

package_state: latest

Create the templates¶

– templates/motd.j2

### templates/motd.j2

_____             _          _    _  _                      _ 
/  __ \           | |        | |  | |(_)                    | |
| /  \/  ___    __| |  ___   | |  | | _  ____ __ _  _ __  __| |
| |     / _ \  / _` | / _ \  | |/\| || ||_  // _` || '__|/ _` |
| \__/\| (_) || (_| ||  __/  \  /\  /| | / /| (_| || |  | (_| |
\____/ \___/  \__,_| \___|   \/  \/ |_|/___|\__,_||_|   \__,_|

{{ motd_message }}

System information:
-------------------

OS:         {{ ansible_distribution }} {{ ansible_distribution_version }}
Hostname:   {{ inventory_hostname }}

{{ custom_message | default('') }}

– templates/node-server.j2

### templates/node-server.j2
const
    // Set the server port which will be listening to
    // Those 2 values are passed from the env file
    SERVER_PORT = 5000,
    SERVER_NAME = "{{ inventory_hostname }}";

// Create the basic http server
require('http')
    .createServer((request, response) => {

        // Send reply to user
        response.end(`<h1>Hello from ${SERVER_NAME}.</h1>`);

    }).listen(SERVER_PORT, () => {
        // Notify users that the server is up and running
        console.log(`${SERVER_NAME} is up. 
            Please click or point your browser to:
            http://localhost:${SERVER_PORT}`);
    });

Create the tasks for the role¶
In this example we will have multiple tasks for learning purposes.
We will need to create the tasks for each role.
Once the tasks are ready, we can define them in the main task file.

— tasks/pre-requirements.yaml

### tasks/pre-requirements.yaml
---
- name: Install Packages
  ansible.builtin.apt:
    name: "{{ item }}"
    state: "{{ package_state }}"
  # Loop over the required packages to install
  with_items: "{{ apt_packages }}"

- name: Verify Packages Installation
  ansible.builtin.command: "{{ item }} --version"
  register: packages_version
  with_items: "{{ apt_packages_verify }}"

- name: Print package version
  ansible.builtin.debug:
    msg: "{{ item.stdout_lines  }}"
  with_items: "{{ packages_version.results }}"

— tasks/node-server.yaml

  ### tasks/node-server.yaml
  ---
  - name: Copy Node server
    ansible.builtin.template:
      src: templates/node-server.j2
      dest: /node-server.js
      mode: 600
    become: true
    become_method: ansible.builtin.su

  - name: Install "pm2" node.js package.
    community.general.npm:
      name: "pm2"
      global: true
    become: true
    become_method: ansible.builtin.su

  - name: Get running node processes
    shell: "ps -ef | grep -v grep | grep -w node | awk '{print $2}'"
    register: running_processes

  - name: Kill running node server (if any)
    shell: "kill {{ item }}"
    with_items: "{{ running_processes.stdout_lines }}"

  - name: Wait for the process to die
    wait_for:
      path: "/proc/{{ item }}/status"
      state: absent
    with_items: "{{ running_processes.stdout_lines }}"
    ignore_errors: true
    register: killed_processes

  - name: Force kill stuck processes
    shell: "kill -9 {{ item }}"
    with_items: "{{ killed_processes.results | select('failed') | map(attribute='item') | list }}"

  - name: Start Node server
    ansible.builtin.command:
      chdir: /
      cmd: "pm2 start -f /node-server.js"
    register: server_status
    changed_when: server_status.rc != 0

  - name: Print server status
    ansible.builtin.debug:
      msg: "{{ server_status.stdout_lines }}"
    when: server_status.rc == 0

  - name: Check server
    uri:
      url: http://localhost:5000
      method: GET
      status_code: 200
    register: server_status

  - name: Print server status
    ansible.builtin.debug:
      msg: "{{ server_status.status }} - {{ server_status.msg }}"

— tasks/motd.yaml

  ### tasks/motd.j2
  ---
  - name: Copy template
    ansible.builtin.template:
      src: templates/motd.j2
      dest: /etc/motd
      mode: preserve
    become: true
    become_method: ansible.builtin.su

— tasks/main.yml

  ### tasks/main.yml
  ---
  - name: Include Pre-Requirements task
    ansible.builtin.include_tasks:
      file: pre-requirements.yaml

  - name: Include motd task
    ansible.builtin.include_tasks:
      file: motd.yaml

  - name: Deploy node server
    ansible.builtin.include_tasks:
      file: node-server.yaml

Create the playbook for the role¶

### 009-role-playbook.yml
---
###
### The playbook for using our role
### 
- name: Executing codewizard_lab_role
  hosts: all
  become: true
  become_method: ansible.builtin.su

  roles:
    - codewizard_lab_role

Lab 009 - Roles¶

01. What are Ansible roles?¶

02. Ansible roles file structure¶

03. Building an Ansible role¶

04. Initialize file structure¶

05. Create the role content¶

Create the defaults/main.yml¶

Create the templates¶

Create the tasks for the role¶

Create the playbook for the role¶

Create the `defaults/main.yml`¶