Python Docker Remote Debugging VS Code

Question

trying to get remote debugging for my python flask API I have. I'm able to docker-compose up and have postman successfully call the running container, but when I try to attach the debugger, it never compiles. Below is my yml, dockerfile and vscode launch settings... the following error I get is:

There was an error in starting the debug server. Error = {"code":"ECONNREFUSED","errno":"ECONNREFUSED","syscall":"connect","address":"127.0.0.1","port":5050}

version: '2'

services:
  website:
    build: .
    command: >
      python ./nomz/app.py
    environment:
      PYTHONUNBUFFERED: 'true'
    volumes:
      - '.:/nomz'
    ports:
      - '5000:5000'
      - '5050'

DockerFile

FROM python:3.6-slim

ENV INSTALL_PATH /nomz
RUN mkdir -p $INSTALL_PATH

WORKDIR $INSTALL_PATH

COPY requirements.txt requirements.txt
RUN pip3 install -r requirements.txt

COPY . .

EXPOSE 5000 5050

VSCode Launch Settings

{
  "name": "Python: Attach",
  "type": "python",
  "request": "attach",
  "localRoot": "${workspaceFolder}/nomz/app.py",
  "remoteRoot": "/nomz/",
  "port": 5050,
  "host": "localhost"
}

Answer 1

I finally got it working with remote debugging. I had to pip3 install ptvsd==3.0.0 on my local, and make sure that the requirements.txt for my docker container had the same version. (note: the latest version 3.2.1 didn't work)

@BrettCannon had the right link for a good tutorial https://code.visualstudio.com/docs/python/debugging#_remote-debugging

What I had to do was add some code to the app.py of the flask app. I originally was getting address already in use error when starting the container, so I added the socket code and after the first successful attach of debugger I didn't seem to need it anymore (strange I know, but that's why I left it in in case someone else gets that error)

try:
    import ptvsd
    # import socket
    # sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    # sock.close()
    ptvsd.enable_attach(secret=None,address=('0.0.0.0',5050))
    ptvsd.wait_for_attach()
except Exception as ex:
    print('Not working: ')

also i took the debug kwarg off the app.run() in app.py for the flask app. This all gave me the ability to connect the debugger, but the breakpoints where "Unverified", so the last thing that had to happen was a path to the app.py in the launch.json for the remoteRoot. I will say I created a small test api to get this working, and it only need the first level of pathing (ie. /app and not /app/app/app.py)Here is a github of the test api I made (https://github.com/tomParty/docker_python). So if the debugger is attaching, but your breakpoints are unverified, play around with the path of the remoteRoot

"remoteRoot": "/nomz/nomz/app.py"