Docker compose usage of external firebird service

Question

The architecture of the app I planning to create consist of an React, Python and Firebird component. The React part will serve as front-end, the Python part will be the back-end which communicates with the Firebird DB. The React and Firebird component will run in Docker and has to communicate with a Firebird server, which runs locally on 127.0.0.1.

The current docker-compose file looks like the following:

version: "3.9"
services:
  gui:
    build:
      context: gui
    restart: always
    ports:
      - 80:80
    depends_on:
      - api

  api:
    build:
      context: api
    restart: always
    ports:
      - 8000:8000
      - 3050:3050
    volumes:
      - C:/Program Files/Firebird/Firebird_2_5/examples/empbuild:/app/api/empbuild:rw

For connecting to the local Firebird server, the following code can be used:

import firebirdsql

conn = firebirdsql.connect(
    host='127.0.0.1',
    database='...',
    port=3050,
    user='sysdba',
    password='masterkey'
)

So, I need to establish a connection to the local network within the docker container to 127.0.0.1:3050. Currently I'm getting the following error:

ConnectionRefusedError: [Errno 111] Connection refused

Which is due to that the Firebird service is running outside the container and is not mapped to the network of the docker containers. How can I establish this connection by having those two components communicating with the Local Firebird sever?

Answer 1

First, you can't access host from docker container using 127.0.0.1.

Second, if your Firebird is run on host, you shouldn't expose port 3050 from your api container. And even if it runs inside api container, you still shouldn't expose it: use default network created by docker compose, to connect from gui to api using introduced DNS record: api.