[Python] Traefik: Stream dataflow between application does not work

I have the following and basic docker setup where the factory-service creates a continues dataflow which is exposed through Fast API and shall be consumed by another container verification-service. Between both container I want to use Traefik to function as Load Balancer.

I'm able to consume the data stream directly using http://localhost:8001/stream and also through Traefik http://factory.localhost/stream. But unfortunately I'm not able to consume the stream in another docker container.

FastAPI in factory-service:

@app.get("/stream")
async def stream_data():
return StreamingResponse(generate_sensor_data(), media_type="text/event-stream")


verification-service:

import requests

print("Connecting ...")
response = requests.get("http://factory.localhost/stream", stream=True)
print(response.status_code, response.text)


Docker-compose:

services:
factory-service:
build:
context: ./factory
dockerfile: Dockerfile
container_name: factory_service
ports:
- "8001:8001"
labels:
- "traefik.enable=true"
- "traefik.http.routers.factory.rule=Host(`factory.localhost`)"
- "traefik.http.services.factory.loadbalancer.server.port=8001"
- "traefik.http.middlewares.sse.headers.customResponseHeaders.Access-Control-Allow-Origin=*"
- "traefik.http.middlewares.sse.headers.customResponseHeaders.Cache-Control=no-cache"
- "traefik.http.middlewares.sse.headers.customResponseHeaders.Connection=keep-alive"
- "traefik.http.routers.factory.middlewares=sse"
- "traefik.http.routers.factory.entrypoints=web"
networks:
- app-network

verification-service:
build:
context: ./verification
dockerfile: Dockerfile
container_name: verification_service
depends_on:
factory-service:
condition: service_started
networks:
- app-network

traefik:
image: traefik:v3.3
command:
- "--log.level=DEBUG"
- "--api.insecure=true"
- "--providers.docker"
- "--providers.docker.exposedbydefault=false"
- "--entryPoints.web.address=:80"
ports:
- "80:80"
- "8080:8080"
volumes:
- /var/run/docker.sock:/var/run/docker.sock
networks:
- app-network

networks:
app-network:
driver: bridge


I already saw the following questions and good documentation from flexguse but I'm not able to translate their solution into my case

Traefik: HTTPS access between applications does not work

https://github.com/flexguse/traefik-inter-container-routing

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