Understanding sample application

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

How to do it...

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.