How to debug a Flask app which runs with gunicorn in a container?

Question

I have been looking for a way to start a python debugger so I can debug my flask app which is being executed with gunicorn inside a docker container and then connect to it with my VSCode from outside.

But I dont find any solutions. In fact someone here suggests that it is not possible at all?

Is there a way to debug my flask app executed by gunicorn?

Answer 1

So it looks like this is very difficult, if not impossible atm, to do with gunicorn. So what I did was

1. Create a degub_app.py file in my project with :

 from myapp.api import create_app if __name__=="__main__": app = create_app() app.run('0.0.0.0', 8000, debug=False)

2. I created a debug container which runs nothing on start it just waiting idle like this in my docker-compose file:

 api-debug: image: "myapp:latest" restart: on-failure:3 environment: volumes: - ./:/usr/src/app depends_on: - rabbitmq - redis - mongo tty: true stdin_open: true command: tail -F anything ports: - 8000:8000

3. Then using VSCode with the Remote Container pluggin i attached to that container. This starts a new VSCode window and shows you the files inside the container.

Note Since the VSCode is now connected to the container I had to re-install the Python extension (you can look this up but it is easy just go to pluggins and re-install to container)

4. I created a launch.json inside the container to run the degub_app.py that I mentioned above like this:

{ "version": "0.2.0", "configurations": [ { "name": "Python: Debug API", "type": "python", "request": "launch", "program": "${workspaceFolder}my_path/debug_api.py", "console": "integratedTerminal", "justMyCode": false } ] }