Routing not working properly with multiple Host() and Mount() objects #2243

nicolaipre · 2023-08-07T20:00:28Z

nicolaipre
Aug 7, 2023

Hi.

I am currently using starlette==0.31.0 and I recently encountered a weird bug where my routing broke which I couldn't figure out why at first. I decided to strip down my code to only the problematic parts in an attempt to identify the cause.

It turns out there is a problem with the routing in Starlette when you use multiple Host() and Mount() objects although this should work fine according to the docs. as described here: https://www.starlette.io/routing/#submounting-routes

Routing of the first Host() or Mount works perfectly fine, but if you add a second instance to your list of routes, only the first one works. I tried to remove the Host() objects, but the same thing happens if you have two Mount() objects.

After updating your hosts file with 127.0.0.1 api.example.com, the problem can be demonstrated by running the piece of code below, and accessing the following endpoints:

http://api.example.com:8000/ -> 200 OK
http://api.example.com:8000/foo/foo -> 200 OK
http://api.example.com:8000/bar/bar -> 404 Not Found

from starlette.applications import Starlette
from starlette.routing import Host, Mount, Route, Router
from starlette.responses import HTMLResponse, JSONResponse, PlainTextResponse
from starlette.schemas import SchemaGenerator
import uvicorn

async def openapi(request):
    spec = {
        "openapi": "3.0.0", 
        "info": {
            "title": "Example API", 
            "version": "1.1"
        }
    }
    schema = SchemaGenerator(spec)
    
    # OpenAPIResponse returns incorrect data. 
    # Should return `JSONResponse(schema.get_schema(routes=request.app.routes))` for correct data for Redoc
    #return schema.OpenAPIResponse(request=request)
    return JSONResponse(schema.get_schema(routes=request.app.routes))

async def redoc(request):
    html = f"""
        <!DOCTYPE html>
        <html>
          <head>
            <title>Redoc</title>
            <meta charset="utf-8"/>
            <meta name="viewport" content="width=device-width, initial-scale=1">
            <link href="https://fonts.googleapis.com/css?family=Montserrat:300,400,700|Roboto:300,400,700" rel="stylesheet">
          </head>
          <body>
            <redoc spec-url="{request.url.scheme}://{request.url.netloc}/openapi.json"></redoc>
            <script src="https://cdn.redoc.ly/redoc/latest/bundles/redoc.standalone.js"> </script>
          </body>
        </html>
    """
    return HTMLResponse(html)

async def home(request):
    """
    description: home endpoint
    """
    return PlainTextResponse("home")

async def foo(request):
    """
    description: foo endpoint
    """
    return PlainTextResponse("foo")

async def bar(request):
    """
    description: bar endpoint
    """
    return PlainTextResponse("bar")


ROUTES = [
    Route("/",             endpoint=home),
    Route("/openapi.json", endpoint=openapi, include_in_schema=False),
    Route("/redoc",        endpoint=redoc,   include_in_schema=False),
    
    # Only the first instance of a Host() or Mount() works = 200 OK
    Host("api.example.com", name="Foo Routes", app=Router(routes=[
        Mount("/foo", name="Foo", routes=[
            Route("/foo", foo, name="Foo")
        ]),
    ])),
    
    # The second Host() or Mount() does not work = 404 Not Found
    Host("api.example.com", name="Bar Routes", app=Router(routes=[ # Same thing happens if you comment out Host() and only use Mount()'s instead.
        Mount("/bar", name="Bar", routes=[
            Route("/bar", bar, name="Bar")
        ])
    ])),
]

for r in ROUTES:
    print(r)

app = Starlette(routes=ROUTES)

if __name__ == '__main__':
    uvicorn.run("example:app", host='0.0.0.0', port=8000, reload=True)

Additionally, OpenAPIResponse seems to be returning yaml instead of JSON, which makes Redoc break in the latest version of Starlette. This can be replaced with JSONResponse(schema.get_schema(routes=request.app.routes)) for intended functionality.

nicolaipre · 2023-08-19T12:13:23Z

nicolaipre
Aug 19, 2023
Author

Please let me know if this is user error, but I have tested this multiple times now and cannot see why it shouldn't be working.

Edit:
I did some more testing and it seems that one cannot register multiple Host() objects for the same subdomain.

The reason I want to be able to register multiple Host() objects for the same subdomain is because I register my routes in sections (or blocks...) with custom route registration like this:

RouteGroup(
    domain="api.domain.com",
    middleware=["auth"],
    name="Rules", 
    prefix="/api", 
    routes=[
        GET("/rules", RuleController.rules_all).name("all_rules"),
        POST("/rule", RuleController.rule_new).name("new_rule"),
    ]
),

RouteGroup(
    domain="api.domain.com",
    middleware=["auth"],
    name="Tasks", 
    prefix="/api", 
    routes=[
        GET("/tasks", TaskController.all).name("all_tasks"),
        POST("/task", TaskController.new).name("new_task"),
    ]
),

Now that I have found the problem I could iterate over all added routes and inject routes into the same Host() object to solve the problem.

I suppose this is a case of: it is not a bug, it is a feature - However it would be amazing to have support for this (Multiple Host() objects with the same domain) in Starlette by default as it already exists in other frameworks such as Sanic - see example below where you have 2 separate Blueprint objects (almost equivalent to Host() objects in Starlette) with the same domain specified:

# pip install sanic
from sanic import Sanic
from sanic import Blueprint
from sanic import response
from sanic.request import Request
from sanic.response import text as PlainTextResponse

async def home(request: Request):
    return PlainTextResponse("home\n")

async def foo(request: Request):
    return PlainTextResponse("foo\n")

async def bar(request: Request):
    return PlainTextResponse("bar\n")

foo_routes = Blueprint("Foo_Routes", url_prefix="/foo", host="api.example.com:8000")
foo_routes.add_route(foo, "/foo") # 200 OK

bar_routes = Blueprint("Bar_Routes", url_prefix="/bar", host="api.example.com:8000")
bar_routes.add_route(bar, "/bar") # 200 OK
    
ROUTES = [
    foo_routes, 
    bar_routes
]

app = Sanic("test")
app.blueprint(ROUTES)

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=8000, debug=True)

0 replies

nicolaipre · 2023-08-20T13:58:36Z

nicolaipre
Aug 20, 2023
Author

Opened related issue: #2248

0 replies

nicolaipre · 2023-09-06T13:40:59Z

nicolaipre
Sep 6, 2023
Author

Closing the discussion as @aminalaee has solved this in PR: #2263

Hopefully merged soon.

0 replies

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Routing not working properly with multiple Host() and Mount() objects #2243

nicolaipre Aug 7, 2023

Replies: 3 comments

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