Getting ASGI message error when using an URL prefix

[wdroz]

Description

Since version higher than 1.4.7, I can no longer make nicegui works when using a custom URL prefix.

Basically it's the same error as #2354, #2368 and #2370.

When I try locally, without prefix, this work perfectly. All dependencies are identical between local and production. The only diff is that in prod, the app is behind a reverse proxy with a prefix for the URL.

wss://company.domain/subdomain/subsubdomain/subsubsubdomain/_nicegui_ws/socket.io/?client_id=REDACTED&transport=websocket.

I'm not knowledgeable with socketio, but the fix that set the socketio_path seem to use absolute URL here.

The current way of using custom prefix is by using the request object here but the same trick seem impossible at startup.

[wdroz]

I wasn't able to reproduce it using the subpath example examples/nginx_subpath. Maybe this is because the middleware intercept X-Forwarded-Prefix but not the root_path?

https://github.com/zauberzeug/nicegui/blob/main/nicegui/middlewares.py

[rodja]

I finally had time to look into this but could not quickly create a test setup. Could you share a minimal reproducible example? Why do you supply root_path at all? As you said the examples/nginx_subpath works fine without. And so does our docker-compose.yml test-setup which uses a Traefik proxy:

nicegui/docker-compose.yml

Lines 14 to 16 in 9dd03ee

	- traefik.http.middlewares.app-prefix.stripprefix.prefixes=/app
	- traefik.http.middlewares.app-prefix.stripprefix.forceSlash=false # see https://doc.traefik.io/traefik/middlewares/stripprefix/#forceslash
	- traefik.http.routers.app.middlewares=app-prefix

[rodja]

The error may very well be caused by the same problem as in #2515, which hopefully gets fixed with my pull request in the python-engineio repository.

[rodja]

@wdroz could you share a minimal demo which we can use to verify that #2521 really fixes your issue?

[wdroz]

I tried to make a docker compose that do the same as our k8s and adapt the nginx_subpath example with it.

changes in nginx.conf

server {
        listen 80 default_server;
        server_name _;
        resolver 127.0.0.11; # see https://github.com/docker/compose/issues/3412

        location ~ ^/nicegui/(/|$)(.*) {
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection $connection_upgrade;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;

            proxy_pass http://app:8080/$2$is_args$args;
        }
    }

changes in docker-compose.yml

    image: zauberzeug/nicegui:1.4.7
    environment:
      PATH_PREFIX: "/nicegui"
    volumes:
      - ./app:/app # mount local app directory
    command: ["uvicorn", "--host", "0.0.0.0", "--port", "8080", "--root-path", "/nicegui", "main:app"]

changes in app/main.py

from nicegui import ui
from starlette.middleware.sessions import SessionMiddleware
from fastapi import FastAPI

app = FastAPI(
    title="Minimal example for prefix root_path",
)

def init(app: FastAPI) -> None:

    app.add_middleware(SessionMiddleware, secret_key="is_this_working?")
    @ui.page('/subpage')
    def subpage():
        ui.label('This is a subpage')
        ui.button('back', on_click=lambda: ui.open('/'))


    @ui.page('/')
    def index():
        ui.button("go to subpage", on_click=lambda: ui.open('/subpage'))


init(app)
ui.run_with(app)

Some relevant fragment of the k8s ingress config

  annotations:
    kubernetes.io/ingress.class: "nginx"
    nginx.ingress.kubernetes.io/rewrite-target: /$2

rules:
    - host: our.company.com
      http:
        paths:
          - path: /nicegui(/|$)(.*)
            pathType: Prefix
            backend:
              service:
                name: app-dev
                port:
                  number: 80

The nginx conf still has some issues as moving from http://localhost/nicegui/ to http://localhost/nicegui/subpage doesn't seem to work. Maybe you know better than me about k8s and nginx and can do something.

But the core is running alongside FastAPI and using uvicorn with --root-path. Also not using the proxy_set_header X-Forwarded-Prefix /nicegui;.