Flask Project

• This is a Flask project to demonstrate how to build a RESTful API with Docker`.

Requirements

• Docker

Build and Run

• Build the docker image using the below command

sudo docker build -t kingsflaskapp:latest .

• After the app is built run it using below command

sudo docker run -d -p someFreeSystemPort:5000 kingsflaskapp:latest # Replace someFreeSystemPort with unused system ports else use 5000 itself 

• Congratulations your flask app is up and running, now open the Browser and you can see the Flask App Up and Running.

Dockerfile Description

FROM python:3
MAINTAINER "S M Y ALTAMSH <[email protected]>"
WORKDIR /app
ADD app/requirements.txt /app
RUN apt-get update
RUN pip install -r requirements.txt
ADD app/ /app
CMD python app.py

COMMAND	DESCRIPTION
FROM python:3.6-alpine	specifies the OS/Base Image from which the application is getting built.
MAINTAINER "S M Y ALTAMSH [email protected]"	Maintainer Details.
WORKDIR /app	Our Flask Application code resides in /app of the docker container so changing directory to /app.
ADD app/requirements.txt /app	copying only "requirements.txt" to install flask dependencies.
RUN apk update	Updating the docker cache and refreshing the container image repositories.
RUN pip install -r requirements.txt	Installing the dependencies in the container image.
ADD app/ /app	Copy the code files and static contents. TIP: [Always keep changing data at the last to build the image faster].
CMD python app.py	Run the flask application at startup.

Try out the docker image.

sudo docker run -d -p 1111:5000 --name flaskrestapi kingalt/flask:1.1

• Check the logs of the application running.

sudo docker logs -f flaskrestapi

• TO Remove the conatiner

sudo docker rm -f flaskrestapi

API ENDPOINTS

• There are 3 APIS which are exposed by the APP.

API-ENDPOINT	DESCRIPTION
"http://localhost:1111/"	This Displays the starting page.
"http://localhost:1111/myinfo"	This gives the developer description.
"http://localhost:1111/status"	This gives the health check details of the API.

• Open the browser and play with these flask app API's.

Tree Structure of the flask app

.
├── app
│   ├── app.py
│   ├── requirements.txt
│   ├── static
│   │   └── tiger.jpg
│   └── templates
│       └── index.html

• "app" directory contains the Entire Flask Application
• The File "app.py" contains the application code
• The File "requirements.txt" contains the pre-requisites for the flask app to work.
• static contents of the html files like images go inside the "static" directory.
• "templates" folder contains the html pages that our app.py uses to render the website.

App file description

@app.route("/myinfo", methods = ['GET'])
events.add('type : webpage' , 'endpoint : /')
def myinfo():
    return jsonify(
        quote="The King Never Fails To Win His Destiny",
        name="S M Y ALTAMSH",
        profession="DevOps Engineer",
        github="https://github.com/smyaltamash/",
        status="200"
    )

@app.errorhandler(404)
events.add('type : request','File Not Found')
def invalid_route(e):
    logging.info(e)
    events.add('type : request',e) 
    return render_template('index.html')

CODE	DESCRIPTION
@app.route("/myinfo", methods = ['GET'])	This indicates the API ENDPOINT for the flask application and the allowed method is "GET".
return jsonify	This is used to return json responses, the First part is the key and the second part is the value.
logging.info(e)	logging to the stdout/file by the logger module for the error captured in @app.errorhandler(404)
events.add	used to add custom message to telemetry events
@app.errorhandler(404)	This is like an error handler for the image if we get 404 status code the below function will be called.

Imports in app.py

import logging                                                     
from flask import jsonify, Flask, render_template, url_for         
from flask_events import Events                                    
from datetime import datetime                                      
import requests                                                    

IMPORTS	DESCRIPTION
logging	logging module for the program
jsonify	Used to convert the responses to json
Flask	FOr the functioning of flask app
render_template	Used to Display HTML pages
url_for	Used to redirect Requests
Events	Used to generate telemetry events
datetime	used to get the timestamp
requests	used to get the status code of the URL's

"requirements.txt" File details

Requirements	Details
flask/Flask	installing dependencies for the flask framework
flask-events	used to record Flask Events [https://github.com/get-wrecked/flask-events]
requests	used to call the http/s endpoints and get the status code