This mini-tutorial describes how to build Docker image and deploy containerized application on Atomic host using Ansible Playbook.
Building Docker image for an application and running container/cluster of containers is nothing new. But the idea is to automate the whole process and this is where Ansible playbooks come in to play.
Note: You can use any Cloud/Workstation based Image to execute the following task.
How to automate the containerization and deployment process for a simple Flask application
First, let’s create a simple Flask Hello-World application. This is the directory structure of the entire application. You can copy these files from the repository trishnaguha/fedora-cloud-ansible:
flask-helloworld/
├── ansible
│ ├── ansible.cfg
│ ├── inventory
│ └── main.yml
├── Dockerfile
└── flask-helloworld
├── hello_world.py
├── static
│ └── style.css
└── templates
├── index.html
└── master.html
hello_world.py:
from flask import Flask, render_template
APP = Flask(__name__)
@APP.route('/')
def index():
return render_template('index.html')
if __name__ == '__main__':
APP.run(debug=True, host='0.0.0.0')
static/style.css:
body {
background: #F8A434;
font-family: 'Lato', sans-serif;
color: #FDFCFB;
text-align: center;
position: relative;
bottom: 35px;
top: 65px;
}
.description {
position: relative;
top: 55px;
font-size: 50px;
letter-spacing: 1.5px;
line-height: 1.3em;
margin: -2px 0 45px;
}
templates/master.html:
<!doctype html>
<html>
<head>
{% block head %}
<title>{% block title %}{% endblock %}</title>
{% endblock %}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" integrity="sha384-1q8mTJOASx8j1Au+a5WDVnPi2lkFfwwEAa8hDDdjZlpLegxhjVME1fgjWPGmkzs7" crossorigin="anonymous">
<link href="https://maxcdn.bootstrapcdn.com/font-awesome/4.6.3/css/font-awesome.min.css" rel="stylesheet" integrity="sha384-T8Gy5hrqNKT+hzMclPo118YTQO6cYprQmhrYwIiQ/3axmI1hQomh7Ud2hPOy8SP1" crossorigin="anonymous">
<link rel="stylesheet" href="{{ url_for('static', filename='style.css') }}">
<link href='http://fonts.googleapis.com/css?family=Lato:400,700' rel='stylesheet' type='text/css'>
</head>
<body>
<div id="container">
{% block content %}
{% endblock %}</div>
</body>
</html>
templates/index.html:
{% extends "master.html" %}
{% block title %}Welcome to Flask App{% endblock %}
{% block content %}
<div class="description">
Hello World</div>
{% endblock %}
Here’s the Dockerfile to build the image. Remember to put your name and email after MAINTAINER:
FROM fedora
MAINTAINER YOUR NAME HERE<your@email.address>
RUN dnf -y update && dnf -y install python-flask python-jinja2 && dnf clean all
RUN mkdir -p /app
COPY files/ /app/
WORKDIR /app
ENTRYPOINT ["python"]
CMD ["hello_world.py"]
That’s everything we need to build the container. Now let’s automate it.
Ansible playbook for our application
Create Inventory file:
[atomic]
<IP_ADDRESS_OF_HOST> ansible_ssh_private_key_file=<'PRIVATE_KEY_FILE'>
Replace IP_ADDRESS_OF_HOST with the IP address of the atomic/remote host and ‘PRIVATE_KEY_FILE’ with your private key file.
Create ansible.cfg file:
[defaults]
inventory=inventory
remote_user=<USER>
[privilege_escalation]
become_method=sudo
become_user=root
Replace USER with the user of your remote host (Atomic).
Create the Playbook main.yml file:
---
- name: Deploy Flask App
hosts: atomic
become: yes
vars:
src_dir: [Source Directory]
dest_dir: [Destination Directory]
tasks:
- name: Create Destination Directory
file:
path: "{{ dest_dir }}/files"
state: directory
recurse: yes
- name: Copy Dockerfile to host
copy:
src: "{{ src_dir }}/Dockerfile"
dest: "{{ dest_dir }}"
- name: Copy Application to host
copy:
src: "{{ src_dir }}/flask-helloworld/"
dest: "{{ dest_dir }}/files/"
- name: Make sure that the current directory is {{ dest_dir }}
command: cd {{ dest_dir }}
- name: Build Docker Image
command: docker build --rm -t fedora/flask-app:test -f "{{ dest_dir }}/Dockerfile" "{{ dest_dir }}"
- name: Run Docker Container
command: docker run -d --name helloworld -p 5000:5000 fedora/flask-app:test
...
Replace [Source Directory] in src_dir field in main.yml with your /path/to/src_dir of the current host.
Replace [Destination Directory] in dest_dir field in main.yml with your /path/to/dest_dir of the remote atomic host.
Issue the following command in order to run the playbook. Make sure you are in the ansible directory.
$ ansible-playbook main.yml.
To verify whether the application is running, you can curl the localhost on your remote atomic host with
$ curl http://localhost:5000.
You can also manage your containers running on remote host using Cockpit. Check this article to know how to use Cockpit to manage your containers: Manage-Containers-with-Cockpit.
Here is the repository that contains Playbooks to deploy containers on Atomic host: trishnaguha/fedora-cloud-ansible.
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