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Ansible tutorial: Deploying our website from git

We've installed apache, pushed our virtualhost and restarted the server safely. Now we'll use the git module to deploy our application.

The git module

Well, this is a kind of break. Nothing necessarily new here. The git module is just another module. But we'll try it out just for fun. And we'll be familiar with it when it comes to ansible-pull later on.

Our virtualhost is set, but we need a few changes to finish our deployment. First, we're deploying a PHP application. So we need to install the libapache2-mod-php package. Second, we have to install git since the git module (used to clone our application's git repository) uses it.

We could do it like this:

...
- name: Installs apache web server
  apt:
    pkg: apache2
    state: present
    update_cache: true

- name: Installs php module
  apt:
    pkg: libapache2-mod-php
    state: present

- name: Installs git
  apt:
    pkg: git
    state: present
...

but Ansible provides a more readable way to write this. Ansible can loop over a series of items, and use each item in an action like this:

...
- name: Installs necessary packages
  apt:
    pkg: "{{ item }}"
    state: latest
    update_cache: true
  with_items:
    - apache2
    - libapache2-mod-php
    - git
...

Note: the use of a loop in a module to invoke it only once is deprecated since version 2.7. You can specify a list of packages as shown in the table below:

Option AOption B
  - name: "Install foo & bar"
  apt:
    pkg: ["foo", "bar"]
 
  - name: "Install foo & bar"
  apt:
    pkg:
      - foo
      - bar

As a result, we ended up with the following playbook:

- hosts: web
  tasks:
    - name: Installs necessary packages
      apt:
        pkg: ["apache2", "libapache2-mod-php", "git"]
        state: latest
        update_cache: true

    - name: Push future default virtual host configuration
      copy:
        src: files/awesome-app
        dest: /etc/apache2/sites-available/awesome-app.conf
        mode: 0640

    - name: Activates our virtualhost
      command: a2ensite awesome-app

    - name: Check that our config is valid
      command: apache2ctl configtest
      register: result
      ignore_errors: true

    - name: Rolling back - Restoring old default virtualhost
      command: a2ensite 000-default
      when: result is failed

    - name: Rolling back - Removing out virtualhost
      command: a2dissite awesome-app
      when: result is failed

    - name: Rolling back - Ending playbook
      fail:
        msg: "Configuration file is not valid. Please check that before re-running the playbook."
      when: result is failed

    - name: Deploy our awesome application
      git:
        repo: https://github.com/leucos/ansible-tuto-demosite.git
        dest: /var/www/awesome-app
      tags: deploy

    - name: Deactivates the default virtualhost
      command: a2dissite 000-default

    - name: Deactivates the default ssl virtualhost
      command: a2dissite default-ssl
      notify:
        - restart apache

  handlers:
    - name: restart apache
      service:
        name: apache2
        state: restarted

Here we go:

$ ansible-playbook -i step-08/hosts -l host1 step-08/apache.yml

PLAY [web] *********************

GATHERING FACTS *********************
ok: [host1]

TASK: [Installs necessary packages] *********************
changed: [host1]

TASK: [Push future default virtual host configuration] *********************
changed: [host1]

TASK: [Activates our virtualhost] *********************
changed: [host1]

TASK: [Check that our config is valid] *********************
changed: [host1]

TASK: [Rolling back - Restoring old default virtualhost] *********************
skipping: [host1]

TASK: [Rolling back - Removing out virtualhost] *********************
skipping: [host1]

TASK: [Rolling back - Ending playbook] *********************
skipping: [host1]

TASK: [Deploy our awesome application] *********************
changed: [host1]

TASK: [Deactivates the default virtualhost] *********************
changed: [host1]

TASK: [Deactivates the default ssl virtualhost] *********************
changed: [host1]

RUNNING HANDLER: [restart apache] *********************
changed: [host1]

PLAY RECAP *********************
host1              : ok=9   changed=8    unreachable=0    failed=0

You can now browse to http://192.168.33.11, and it should display a picture, and the server hostname.

Note the tags: deploy line allows you to execute just a part of the playbook. Let's say you push a new version for your site. You want to speed up and execute only the part that takes care of deployment. Tags allow you to do it. Of course, "deploy" is just a string, it doesn't have any specific meaning and can be anything. Let's see how to use it:

$ ansible-playbook -i step-08/hosts -l host1 step-08/apache.yml -t deploy
X11 forwarding request failed on channel 0

PLAY [web] *********************

GATHERING FACTS *********************
ok: [host1]

TASK: [Deploy our awesome application] *********************
changed: [host1]

PLAY RECAP *********************
host1              : ok=2    changed=1    unreachable=0    failed=0

Ok, let's deploy another web server in step-09.