Instruction	Comments
image: easygeoip_app	Name of the docker image after build
build: .	Instruct docker compose to build the image with the Dockerfile under the current directory
command: ["python", "/srv/app/main.py"]	Change the default command so that the application can be restarted whenever the source code is updated
volumes	Mount the current directory at /srv/app in the application's container. This is very handy, since an update to the source code won''t require rebuilding the Docker Image (and hence restarting the application container)
ports	Map port 5000 on the container to port 5000on the host. default all Flask's application use port 5000 the web server port so we're just making sure that it's accessible.
environment	Here were passing the environment variables required by the application. DEBUG=1 it's very important since Flask will restart the application whenever the source code is updated.