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: yesIn 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: yesAccordingly, 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.
