dmccuk · July 29, 2022 14:08
diff --git a/simple_role_dmo b/simple_role_dmo
 let an Ansible role from scratch and do the following things, and then deploy the role.

  * Create the role
  * Setup the tasks using best practice
  * Add templates with ansible facts
  * Setup handlers for when things change
  * Make the whole thing idempotent and not task run unless it needs to
  * Show how variable precedence works for default, vars & group_vars

 All the code for this demo is available below. Don't forget to like and subscribe!

 ** NOTE **
   These code samples below are the finished code. As part of the demo, I will be building these up step by step. **
 **

 1) Create the role.

 ````
 mkdir roles
 cd roles
 ansible-galaxy init webserver
 tree webserver

 webserver/
 ├── defaults
 │   └── main.yml
 ├── files
 ├── handlers
 │   └── main.yml
 ├── meta
 │   └── main.yml
 ├── README.md
 ├── tasks
 │   └── main.yml
 ├── templates
 ├── tests
 │   ├── inventory
 │   └── test.yml
 └── vars
    └── main.yml
 ````

 2) Lets setup out tasks using best practice. Best practice is to move the tasks out of the main.yml, and into their own tasks.
 For example, lets use and install.yml to only install and start the service, then have a configure.yml to only contain tasks
 to configure the application.

 ````
 vi webserver/tasks/main.yml
 ---
 - name: include role tasks
  include_tasks: "{{ webserver_tasks }}"
  loop:
    - install.yml
    - configure.yml
  loop_control:
    loop_var: webserver_tasks



 vi webserver/tasks/install.yml

 - name: install the latest version of Apache
  yum:
    name: httpd
    state: latest

 - name: start the service
  service:
    name: httpd
    state: started

 - name: add rule to FW
  firewalld:
    service: http
    permanent: true
    state: enabled
  notify: restart firewalld
 ````

 To be able to run the role, it's good to have an ansible.cfg file, a hosts.ini file and a deployment file:

 ````
 vi ansible.cfg
 [defaults]
 inventory=hosts.ini

 vi hosts.ini
 [webserver]
 172.31.17.134

 [webserver:vars]
 ansible_user=ec2-user
 ansible_ssh_private_key_file=~/.ssh/working.pem

 vi deploy.yml
 ---
 - name: deploy a webserver
  hosts: webserver
  become: true
  roles:
    - webserver
 ````


 3) Add the template to create the webpage

 ````
 - name: create webpage
  template:
    src: templates/index.html.j2
    dest: /var/www/html/index.html
  notify: restart httpd

 vi webserver/templates/index.html.j2

 <!doctype html>
 <title>LondonIAC meetup - Site Maintenance</title>
 <style>
  body { text-align: center; padding: 150px; }
  h1 { font-size: 50px; }
  body { font: 20px Helvetica, sans-serif; color: #333; }
  article { display: block; text-align: left; width: 650px; margin: 0 auto; }
  a { color: #dc8100; text-decoration: none; }
  a:hover { color: #333; text-decoration: none; }
 </style>

 <article>
    <h1>We&rsquo;ll be back soon!</h1>
    <div>
        <p>Sorry for the inconvenience but we&rsquo;re performing some maintenance at the moment. If you need to you can always <a href="mailto:#">contact us</a>, otherwise we&rsquo;ll be back online shortly!</p>
        <p> Message brought to you by: {{ ansible_hostname }} and variable: {{ variable }}</p>
    <img src="https://marcelorjava.files.wordpress.com/2014/04/dilbert.gif" alt="Dilbert">
        <p>&mdash; The Team</p>
    </div>
    <p>
 </p>
 </article>

 ````

 4) Lets setup the handlers so we can restart services when something changes

 ````
 vi webserver/handlers/main.yml

 ---
 - name: restart httpd
  service:
    name: firewalld
    state: restarted

 - name: restart httpd
  service:
    name: httpd
    state: restarted
 ````

 5) Lets add a variable to our code so we can follow how variable prececdence works.

 ````
 vi webserver/defaults/main.yml
 ---
 variable: one
 ````

 Update the index.html template and add a veriable so we can see the output change.

 Now run ansible to see it add the variable to the webpage.

 Now add a new variable to vars.
 ````
 vi webserver/vars/main.yml
 ---
 variable: two
 ````

 Re-run ansible. Does the value change?

 Now lets setup group_vars and create a host variable file. 

 ````
 mkdir group_vars
 vi group_vars/webserver.yml
 ---
 variable: three
 ````

 Re-run ansible. What do you think will happen?
 As you can see form the output, playbook variables (in vars) beat the group_vars. So lets hash out the vars variable and re-run:

 ````
 vi webserver/vars/main.yml
 ---
 #variable: two
 ````

 Now when we re-run ansible, our host variable is picked up.
	let an Ansible role from scratch and do the following things, and then deploy the role.

	* Create the role
	* Setup the tasks using best practice
	* Add templates with ansible facts
	* Setup handlers for when things change
	* Make the whole thing idempotent and not task run unless it needs to
	* Show how variable precedence works for default, vars & group_vars

	All the code for this demo is available below. Don't forget to like and subscribe!

	NOTE
	These code samples below are the finished code. As part of the demo, I will be building these up step by step. **
	**

	1) Create the role.

	````
	mkdir roles
	cd roles
	ansible-galaxy init webserver
	tree webserver

	webserver/
	├── defaults
	│ └── main.yml
	├── files
	├── handlers
	│ └── main.yml
	├── meta
	│ └── main.yml
	├── README.md
	├── tasks
	│ └── main.yml
	├── templates
	├── tests
	│ ├── inventory
	│ └── test.yml
	└── vars
	└── main.yml
	````

	2) Lets setup out tasks using best practice. Best practice is to move the tasks out of the main.yml, and into their own tasks.
	For example, lets use and install.yml to only install and start the service, then have a configure.yml to only contain tasks
	to configure the application.

	````
	vi webserver/tasks/main.yml
	---
	- name: include role tasks
	include_tasks: "{{ webserver_tasks }}"
	loop:
	- install.yml
	- configure.yml
	loop_control:
	loop_var: webserver_tasks



	vi webserver/tasks/install.yml

	- name: install the latest version of Apache
	yum:
	name: httpd
	state: latest

	- name: start the service
	service:
	name: httpd
	state: started

	- name: add rule to FW
	firewalld:
	service: http
	permanent: true
	state: enabled
	notify: restart firewalld
	````

	To be able to run the role, it's good to have an ansible.cfg file, a hosts.ini file and a deployment file:

	````
	vi ansible.cfg
	[defaults]
	inventory=hosts.ini

	vi hosts.ini
	[webserver]
	172.31.17.134

	[webserver:vars]
	ansible_user=ec2-user
	ansible_ssh_private_key_file=~/.ssh/working.pem

	vi deploy.yml
	---
	- name: deploy a webserver
	hosts: webserver
	become: true
	roles:
	- webserver
	````


	3) Add the template to create the webpage

	````
	- name: create webpage
	template:
	src: templates/index.html.j2
	dest: /var/www/html/index.html
	notify: restart httpd

	vi webserver/templates/index.html.j2

	<!doctype html>
	<title>LondonIAC meetup - Site Maintenance</title>
	<style>
	body { text-align: center; padding: 150px; }
	h1 { font-size: 50px; }
	body { font: 20px Helvetica, sans-serif; color: #333; }
	article { display: block; text-align: left; width: 650px; margin: 0 auto; }
	a { color: #dc8100; text-decoration: none; }
	a:hover { color: #333; text-decoration: none; }
	</style>

	<article>
	<h1>We’ll be back soon!</h1>
	<div>
	<p>Sorry for the inconvenience but we’re performing some maintenance at the moment. If you need to you can always <a href="mailto:#">contact us</a>, otherwise we’ll be back online shortly!</p>
	<p> Message brought to you by: {{ ansible_hostname }} and variable: {{ variable }}</p>
	<img src="https://marcelorjava.files.wordpress.com/2014/04/dilbert.gif" alt="Dilbert">
	<p>— The Team</p>
	</div>
	<p>
	</p>
	</article>

	````

	4) Lets setup the handlers so we can restart services when something changes

	````
	vi webserver/handlers/main.yml

	---
	- name: restart httpd
	service:
	name: firewalld
	state: restarted

	- name: restart httpd
	service:
	name: httpd
	state: restarted
	````

	5) Lets add a variable to our code so we can follow how variable prececdence works.

	````
	vi webserver/defaults/main.yml
	---
	variable: one
	````

	Update the index.html template and add a veriable so we can see the output change.

	Now run ansible to see it add the variable to the webpage.

	Now add a new variable to vars.
	````
	vi webserver/vars/main.yml
	---
	variable: two
	````

	Re-run ansible. Does the value change?

	Now lets setup group_vars and create a host variable file.

	````
	mkdir group_vars
	vi group_vars/webserver.yml
	---
	variable: three
	````

	Re-run ansible. What do you think will happen?
	As you can see form the output, playbook variables (in vars) beat the group_vars. So lets hash out the vars variable and re-run:

	````
	vi webserver/vars/main.yml
	---
	#variable: two
	````

	Now when we re-run ansible, our host variable is picked up.