Playbooks

Playbooks in Ansible are simple YAML file that describe configuration which should be done on a remote server. Playbooks are really simple but very powerful; the tasks mentioned inside the playbook are execute sequentially. YAML is human-readable data serialization format, which cares about whitespace like Python, it represents tree-like structure.

First playbook

Step 1

Create a file myplaybook.yml with the following content:

---
- hosts: demo
  gather_facts: yes
  tasks:
  - name: Install the git package
    apt: 
      name: git
      state: present

Here is the explanation of this playbook:

- hosts: demo is here to tell ansible that this part of the playbook should be applied on server demo This playbook is very simple and apply only on demo, but you will often have playbooks that apply on multiple hosts. Ansible is great tool to orchestrate installation.

gather_facts: yes tells ansible to execute the setup module before doing anything else. The setup module will collects the facts and store them as variables. Those variables can then be used in playbooks. In this demo playbook, we dont use any variable yet, but you will see that later.

tasks:is a list of task that will be applied on the server. For now we only have one task, which is using the module apt to install the git package.

Now run the play:

ansible-playbook myplaybook.yml

After this, your demo server is supposed to have git installed.

Step 2

Add a task to clone a flask application from github: https://github.com/arnaudmorin/demo-flask.git (A flask application is a very simple web server written in python - so basically, it's a website)

---
- hosts: demo
  gather_facts: yes
  tasks:
  - name: Install the git package
    apt: 
      name: git
      update_cache: yes 
      state: present
  - name: Clone my flask application
    git: ...   # complete by yourself
               # see https://docs.ansible.com/ansible/latest/collections/ansible/builtin/git_module.html

Step 3

Add a task to install the flask app. Check the github page https://github.com/arnaudmorin/demo-flask for info on how this apps can be installed (but dont do it manually). Then, add a task to your playbook that will do the installation for you.

Step 4

Add a task to start the app in background.

Step 5

Your demo server is now running the flask application. Unfortunately, this is running in a docker container inside your localhost. So the application is not yet accessible from internet.

What you should do now is to make this application accessible from internet! By chance, the demo container is having port 8080 opened:

docker port demo

will give you:

8080/tcp -> 127.0.0.2:8080
22/tcp -> 127.0.0.2:2222

So, to access demo from internet, you will have to install a proxy server. Here are some tips:

Extend your playbook to not only manage demo but also localhost. For localhost, add a least 2 tasks:
- install nginx
- configure nginx as a proxy (port 80 --> 8080) (google is your friend)
Bonus: How can we restart nginx only after we changed it's configuration? (tip: ansibles handlers)
Bonus2: using some ansible variables to add a debug task to your playbook to print the URL of your website.

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