Prepare a simple Docker Compose project
In this step, we will prepare a simple Docker Compose project. Since Docker Compose is not pre-installed in the LabEx environment, we will first install it. Then, we will create a simple web application and a Docker Compose file to define and run it.
First, let's install Docker Compose. We will download the Docker Compose binary and make it executable.
sudo curl -L "https://github.com/docker/compose/releases/download/v2.20.2/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
sudo chmod +x /usr/local/bin/docker-compose
Now, let's verify the installation by checking the Docker Compose version.
docker-compose --version
You should see the installed version of Docker Compose in the output.
Next, we will create a simple web application. We will use a basic Python Flask application. Create a directory for our project and navigate into it.
mkdir my-web-app
cd my-web-app
Inside the my-web-app directory, create a file named app.py with the following content:
from flask import Flask
app = Flask(__name__)
@app.route('/')
def hello_world():
return 'Hello, Docker Compose!'
if __name__ == '__main__':
app.run(debug=True, host='0.0.0.0')
This is a simple Flask application that returns "Hello, Docker Compose!" when accessed.
Now, we need a Dockerfile to build a Docker image for our Flask application. Create a file named Dockerfile in the my-web-app directory with the following content:
FROM python:3.9-slim
WORKDIR /app
COPY requirements.txt requirements.txt
RUN pip install -r requirements.txt
COPY . .
EXPOSE 5000
CMD ["python", "app.py"]
This Dockerfile uses a slim Python 3.9 image, sets the working directory, copies and installs dependencies from requirements.txt, copies the application code, exposes port 5000, and specifies the command to run the application.
We also need a requirements.txt file for the Flask dependency. Create a file named requirements.txt in the my-web-app directory with the following content:
Flask==2.2.2
Finally, we will create a docker-compose.yml file to define our service. Create a file named docker-compose.yml in the my-web-app directory with the following content:
version: "3.8"
services:
web:
build: .
ports:
- "5000:5000"
This docker-compose.yml file defines a service named web. It tells Docker Compose to build the image using the Dockerfile in the current directory (.) and map port 5000 on the host to port 5000 in the container.
Now, let's build and run the service using Docker Compose. Make sure you are in the ~/project/my-web-app directory.
docker-compose up -d
This command builds the image (if not already built), creates a container for the web service, and starts it in detached mode (-d).
You can check if the container is running using the docker ps command.
docker ps
You should see a container for the my-web-app-web-1 service running.
To verify that the application is working, you can access it using curl.
curl http://localhost:5000
You should see the output "Hello, Docker Compose!".
