Throughout the book, we will give examples of how to deploy an application on the infrastructure created by the Ansible playbooks. We have written a simple phone book application using Python's flask framework (http://flask.pocoo.org). The phone book application listens on port 8080 and we can use any browser to use the phone book. The app has two variations, one uses SQLite as a database whereas the other one uses MySQL. The application code remains the same, we have just used different databases to demonstrate the application running in a single compute instance and it running across multiple instances or even different components of a cloud provider.

The application code can be obtained from:

• Phone book SQLite: https://github.com/ansible-cookbook/phonebook-sqlite
• Phone book MySQL: https://github.com/ansible-cookbook/phonebook-mysql

The application deployment can be done using Ansible. If we are going to deploy the application using SQLite then the following tasks for the phonebook role are good enough:

---
- name: install epel repository
  package:
    name: epel-release
    state: present

- name: install dependencies
  package:
    name: "{{ item }}"
    state: present
  with_items:
  - git
  - python-pip
  - gcc
  - python-devel

- name: install python libraries
  pip:
    name: "{{ item }}"
    state: present
  with_items:
  - flask
  - flask-sqlalchemy
  - flask-migrate
  - uwsgi

- name: get the application code
  git:
    repo: [email protected]:ansible-cookbook/phonebook-sqlite.git
    dest: /opt/phone-book

- name: upload systemd unit file
  copy:
    src: phone-book.service
    dest: /etc/systemd/system/phone-book.service

- name: start phonebook
  systemd:
    state: started
    daemon_reload: yes
    name: phone-book
    enabled: yes

In the case of MySQL, we need to add some more tasks and information to work with Ansible:

---
- name: include secrets
  include_vars: secrets.yml

- name: install epel repository
  package:
    name: epel-release
    state: present

- name: install dependencies
  package:
    name: "{{ item }}"
    state: present
    with_items:
    - git
    - python-pip
    - gcc
    - python-devel
    - mysql-devel 

- name: install python libraries
  pip:
    name: "{{ item }}"
    state: present
  with_items:
  - flask
  - flask-sqlalchemy
  - flask-migrate
  - uwsgi
  - MySQL-python

- name: get the application code
  git:
    repo: [email protected]:ansible-cookbook/phonebook-mysql.git
    dest: /opt/phone-book
    force: yes

- name: upload systemd unit file
  copy:
    src: phone-book.service
    dest: /etc/systemd/system/phone-book.service

- name: upload app config file
  template:
    src: config.py
    dest: /opt/phone-book/config.py

- name: create phonebook database
  mysql_db:
    name: phonebook     
    state: present
    login_host: "{{ mysql_host }}"
    login_user: root
    login_password: "{{ mysql_root_password }}"

- name: create app user for phonebook database
  mysql_user:
    name: app
    password: "{{ mysql_app_password }}"
    priv: 'phonebook.*:ALL'
    host: "%" 
    state: present
    login_host: "{{ mysql_host }}"
    login_user: root
    login_password: "{{ mysql_root_password }}"

- name: start phonebook
  systemd:
    state: started
    daemon_reload: yes
    name: phone-book
    enabled: yes

Accordingly, we will create a secrets.yml in vars directory and encrypt it using ansible-vault. The unencrypted data will look like this:

---
mysql_app_password: appSecretPassword
mysql_root_password: secretPassword
mysql_host: 35.199.168.191

The phone-book.service will take care of initializing the database and running the uwsgi server for serving the application for both SQLite and MySQL based setups:

[Unit]
Description=Simple Phone Book

[Service]
WorkingDirectory=/opt/phone-book
ExecStartPre=/bin/bash /opt/phone-book/init.sh
ExecStart=/usr/bin/uwsgi --http-socket 0.0.0.0:8080 --manage-script-name --mount /phonebook=app:app
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target

Throughout the coming chapters, we will use this role to deploy our phone book application.