Deploying a Minimal Flask App in Docker: Resolving Server Connection Issues

When deploying a Flask application within a Docker container, you may encounter accessibility issues from outside the container. Let's explore the possible reasons and provide a solution to resolve these connection problems.

The issue arises when the application runs on the local interface (127.0.0.1). To make it accessible from outside the container, you need to bind it to the 0.0.0.0 interface, which represents all interfaces on the host machine.

To modify this behavior, update the following code:

if __name__ == '__main__':
    app.run()

to:

if __name__ == '__main__':
    app.run(host='0.0.0.0')

By specifying host='0.0.0.0', you instruct the Flask application to bind to all available interfaces on the host, allowing external access to your containerized application.

Remember that listening on all interfaces may introduce security risks. Refer to https://stackoverflow.com/a/58138250/4332 for guidance on binding to specific interfaces if needed.