Environment Variables

app.py code without Environment Variables

• Applicaition Repository

import os
from flask import Flask
from flask import render_template
import socket
import random
import os

app = Flask(__name__)

color_codes = {
    "red": "#e74c3c",
    "green": "#16a085",
    "blue": "#2980b9",
    "blue2": "#30336b",
    "pink": "#be2edd",
    "darkblue": "#130f40",
    "yellow":"#FFFF00"
}

color = "red"

@app.route("/")
def main():
    #return 'Hello'
    print(color)
    return render_template('hello.html', name=socket.gethostname(), color=color_codes[color])

if __name__ == "__main__":
    app.run(host="0.0.0.0", port="8080")

run app

sudo python3 app.py

view app

---

app.py code with Environment Variables

import os
from flask import Flask
from flask import render_template
import socket
import random
import os

app = Flask(__name__)

color_codes = {
    "red": "#e74c3c",
    "green": "#16a085",
    "blue": "#2980b9",
    "blue2": "#30336b",
    "pink": "#be2edd",
    "darkblue": "#130f40",
    "yellow":"#FFFF00"
}

color = os.environ.get('APP_COLOR')

@app.route("/")
def main():
    #return 'Hello'
    print(color)
    return render_template('hello.html', name=socket.gethostname(), color=color_codes[color])

if __name__ == "__main__":
    app.run(host="0.0.0.0", port="8080")

run app with environment variable

export APP_COLOR=blue; python3 app.py

export APP_COLOR=red; python3 app.py

---

Now dockerize this application

Dockerfile

FROM ubuntu
RUN apt-get update -y
RUN apt-get install python -y
RUN apt-get install python3-pip -y
RUN pip install flask
RUN mkdir /opt/source-code
RUN mkdir /opt/source-code/templates
COPY app.py /opt/source-code/app.py
COPY templates/hello.html /opt/source-code/templates/hello.html
ENTRYPOINT FLASK_APP=/opt/source-code/app.py flask run --host=0.0.0.0

sudo docker build . -t simple-webapp-color

run docker image wit environment variables

• sudo docker run -d -e APP_COLOR=blue -p 5000:5000 simple-webapp-color
• sudo docker run -d -e APP_COLOR=green -p 5001:5000 simple-webapp-color
• sudo docker run -d -e APP_COLOR=pink -p 5002:5000 simple-webapp-color