Build and Deploy a Flask Application Using Docker

This tutorial covers simple steps to build and deploy a Flask application using Docker on Ubuntu 18.04. The sample application process data stored in a JSON file format and displayed on the browser.

Introduction

Docker is an open-source platform to develop, manage, and deploy applications using containers. For Docker installation, refer to this article.

Flask is a web micro-framework built on Python. 

Instructions

Step 1: Create a Dockerfile.

Dockerfile is a first step to containerize an application. Dockerfile contains a list of commands to assemble an image.

# start from base

FROM ubuntu:18.04

LABEL maintainer="Your Name <[email protected]>"

RUN apt-get update -y && \

    apt-get install -y python-pip python-dev

# We copy just the requirements.txt first to leverage Docker cache

COPY ./requirements.txt /app/requirements.txt

WORKDIR /app

RUN pip install -r requirements.txt

COPY . /app

CMD [ "python", "./app.py" ]

Step 2: Create a configuration file to install Flask framework of version 0.10.1

file name: requirements.txt

xxxxxxxxxx

Flask==0.10.1

Step 3: Create a sample JSON data file.

file name: file.json 

xxxxxxxxxx

'{ "name":"John", "age":30, "city":"New York"}'

Step 4: Write Python code to process JSON file data and flush out output to index.html. 

file name: app.py

xxxxxxxxxx

import os

from flask import Flask, render_template, abort, url_for, json, jsonify

import json

app = Flask(__name__,template_folder='.')

# read file

with open('file.json', 'r') as myfile:

    data = myfile.read()

@app.route("/")

def index():

    return render_template('index.html', title="page", jsonfile=json.dumps(data))

if __name__ == '__main__':

    app.run(debug=True, host='0.0.0.0')

Step 5: Index.html file render and display extract on the browser.

file name: Index.html 

xxxxxxxxxx

<!DOCTYPE html>

<html>

<body>

<h2>JSON Data</h2>

<p id="demo"></p>

<script>

 var jsonfile ={{ jsonfile|tojson }};

 var obj = JSON.parse(jsonfile);;

document.getElementById("demo").innerHTML = obj;

</script>

</body>

</html>

Step 1 through 5 setup code and configuration of a Flask application on docker. Now execute the below-mentioned docker command to install and run the sample application.

$docker build -t flask_json:latest

log

xxxxxxxxxx

---> 9d095b8eacb9

Successfully built 9d095b8eacb9

Successfully tagged flask_json:latest

$docker run -p 5000:5000 flask_json

log

xxxxxxxxxx

* Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)

 * Restarting with stat

 * Debugger is active!

 * Debugger PIN: 292-583-301

Conclusion

These basic steps can get you started with the initial setup of a Flask application. This application can further scale to store data into a persistent source and furthermore.