Containerization

Docker Zoo to understand containerization

Run 3 tiny web apps (Cat, Dog, Cow) in separate containers and see how containerization isolates them.

Folder setup

Create a folder for your project:

md docker-zoo
cd docker-zoo

Cat App

Create a new folder:

md cat
cd cat

app.py

from flask import Flask
app = Flask(__name__)

@app.route('/')
def home():
    return "Hi, I’m the Cat app! I live inside my own Docker container."

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=4001)

requirements.txt

flask

Dockerfile

FROM python:3.9-slim
WORKDIR /code
COPY . .
RUN pip install -r requirements.txt
EXPOSE 4001
CMD ["python", "app.py"]

Dog App

Go back and make another folder:

cd ..
md dog
cd dog

app.py

from flask import Flask
app = Flask(__name__)

@app.route('/')
def home():
    return "Woof! The Dog app is barking happily inside its Docker container."

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=4002)

requirements.txt

flask

Dockerfile

FROM python:3.9-alpine
WORKDIR /project
COPY . .
RUN pip install -r requirements.txt
EXPOSE 4002
CMD ["python", "app.py"]

Cow App

cd ..
cd cow
cd cow

app.py

from flask import Flask
app = Flask(__name__)

@app.route('/')
def home():
    return "Moo! The Cow app is grazing peacefully inside its own container."

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=4003)

requirements.txt

flask

Dockerfile

FROM python:3.9-slim
WORKDIR /workspace
COPY . .
RUN pip install --no-cache-dir -r requirements.txt
EXPOSE 4003
CMD ["python", "app.py"]

Build all images

From main docker-zoo/ directory:

docker build -t cat-service ./cat
docker build -t dog-service ./dog
docker build -t cow-service ./cow

Run all containers

docker run -d -p 4001:4001 cat-service
docker run -d -p 4002:4002 dog-service
docker run -d -p 4003:4003 cow-service