I am trying to create a FastAPI app, where I use Traefik to redirect a different URL to the API. I am putting everything in a Docker environment.

Question:

I’m trying to set up a FastAPI app with Traefik to handle requests, using Docker for both services. However, I’m running into an issue where Traefik isn’t resolving the api.localhost domain properly.

Here’s what I’m trying to achieve:

FastAPI should run on a container, and Traefik should route requests to it.
When I try to access `api.localhost`, I receive the error:

Invoke-WebRequest: The remote name could not be resolved: 'api.localhost'

FastAPI app:

@app.get("/")
def get_status():
    return {"status": "running"}

Docker compose:

version: "3.10"

services:
  test_api:
    build:
      context: ./test_api
      dockerfile: Dockerfile
    env_file:
      - .env
    ports:
      - "3000:3000"
    networks:
      - "traefik-internal"
    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.api.rule=Host(`api.localhost`)"
      - "traefik.http.routers.api.entrypoints=web"

  traefik:
    image: traefik:latest
    command:
      - "--api.insecure=true"
      - "--providers.docker=true"
      - "--entrypoints.web.address=:80"
    ports:
      - "80:80"
      - "8080:8080"
    volumes:
      # So that Traefik can listen to the Docker events
      - /var/run/docker.sock:/var/run/docker.sock
    networks:
      - "traefik-internal"

networks:
  traefik-internal:
    name: "traefik-internal"

Problem:

When trying to access http://api.localhost/ via Invoke-WebRequest or a browser, I get the following error:

Invoke-WebRequest: The remote name could not be resolved: 'api.localhost'

What I want to know:

Why can i not access the api using Traefik? Is the request somehow blocked when using the routing by Traefik to the FastAPI? When I get rid of the Traefik services and just try to access localhost:3000/ (where FastAPI app is located), it does work.

Any insights would be greatly appreciated!

What I have tried:

I’ve ensured that the Traefik container is running and listening on port 80 (--entrypoints.web.address=:80).

I’ve confirmed that the test_api container is running and the FastAPI app is accessible on port 3000 inside the container.

I’ve checked the Traefik dashboard on http://localhost:8080, and I can see the rule for api.localhost.