Unable to correctly reverse proxy FastAPI

[ybizeul]

Describe the bug

When using FastAPI behind a proxy that adds path elements like /api/1.0/, there is no way to correctly display the swagger

To Reproduce

1. Configure a reverse proxy to send /api/1.0/ to your FastAPI server
2. access swagger for the API
3. Observe that all your objects are prefixed with /api/1.0

See screenshot

Expected behavior

/api/1.0 should not be part of API documentation.

OpenAPI documents this here

There should be a way to configure Server URL to /api/1.0 like indicated in the examples.

Screenshots

Environment

• OS: alpine docker image
• FastAPI Version 0.54.1
• Python version 3.7.3

Additional context

Using Traefik as reverse proxy. Traefik like other proxies, has the ability to either :
Pass the request as-is with /api/1.0/, or strip the part from the URL and put it in the X-Forwarded-Prefix header. Maybe that could be used as the server URL for Swagger.

[esomir]

You can use openapi_prefix (https://fastapi.tiangolo.com/advanced/sub-applications-proxy/) but that's not really viable when the application doesn't know under which prefix it's running from.

Ideally, it should be resolved dynamically based on the X-Forwarded-Prefix. We are using Traefik and having the same problem. We are having a PathPrefix on our route, and using the StripPrefix middleware, which will strip the prefix, and pass it to the X-Forwarded-Prefix header.

[ybizeul]

That's exactly my situation. Traefik passes all the information but they are not leveraged by fastapi. I switched to Connexion since then

[sm-Fifteen]

Related to #829. @ybizeul raises a good point that the application's root path should probably be included in a server object in the generated OpenAPI documentation and omitted from the routes in the API.

FastAPI's current behavior (not specifying a servers array) falls back to the specification's default, which is this:

If the servers property is not provided, or is an empty array, the default value would be a Server Object with a url value of /.

So equivalent to:

servers:
  - url: '/'

[tiangolo]

Passing the root_path was addressed in #1199 🚀

Available in FastAPI 0.56.0.

Here are new docs on running FastAPI Behind a Proxy with a Traefik example.

It could be passed to Uvicorn as:

$ uvicorn app:main --root-path=/api/1.0

---

About reading the X-Forwarded-Prefix, that would be a feature request to Uvicorn, to read it when using --proxy-headers and set the root_path in the ASGI scope with it.

If it is implemented there, it will be automatically supported here.

[ybizeul]

From what I see in the documentation you point me to, it's not fixed at all and /api/blah is still part of the path for every path

[tiangolo]

Ah, you are right, I didn't interpret your original issue description correctly.

You expected it to not contain the prefix and still work.

I have to investigate how the servers would interact with the rest.

[tiangolo]

This was fixed/implemented by @rkbeatss in #1596. 🎉

Available in FastAPI version 0.59.0. 🚀

New docs here: https://fastapi.tiangolo.com/advanced/behind-a-proxy/#additional-servers

[github-actions]

Assuming the original issue was solved, it will be automatically closed now. But feel free to add more comments or create new issues.

[trungswat]

Hi,

I am still stuck in FastAPI behind Reverse Proxy Nginx.
Everything running smoothly in local query, ROOT_PATH automatically add to every endpoint:

INFO: 172.29.0.5:45328 - "GET /ge_api/ArtistPerformance HTTP/1.1" 200 OK

But when running FastAPI behind the proxy, the ROOT_PATH is double before the endpoint which causes the query to be wrongly directed.

INFO: 172.29.0.9:45668 - "GET /ge_api/ge_api/ArtistPerformance HTTP/1.0" 404 Not Found

Here is FastAPI app config

app = FastAPI(
    root_path = "/ge_api",
    description = desc,
    openapi_tags = tags_metadata,
    version = "0.0.1",
    docs_url = '/ge_api/docs',
    redoc_url = '/ge_api/redoc',
    openapi_url = '/ge_api/openapi.json',
)

Nginx config:

location /ge_api {
			#proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
			#proxy_set_header X-Forwarded-Prefix /ge_api/api;
			#proxy_set_header Host $http_host;
			#proxy_http_version 1.1;
			proxy_pass http://ge_api:8080;	
		}

Is there any fixed for the issue? Thanks

[dontsovcmc]

Is there any fixed for the issue? Thanks

I solved same issue using subapi:
root_path doesn't work for me. openapi_prefix is deprecated.

from fastapi import FastAPI

app = FastAPI()

@app.get("/app")
def read_main():
    return {"message": "Hello World from main app"}

subapi = FastAPI()

@subapi.get("/sub")
def read_sub():
    return {"message": "Hello World from sub API"}

app.mount("/subapi", subapi)

[sm-Fifteen]

Is there any fixed for the issue? Thanks

I solved same issue using subapi: root_path doesn't work for me. openapi_prefix is deprecated.

@dontsovcmc: root_path is intended to be passed to the root app by Uvicorn (and to Uvicorn using the --root-path CLI argument).

Hi,

I am still stuck in FastAPI behind Reverse Proxy Nginx. Everything running smoothly in local query, ROOT_PATH automatically add to every endpoint:

INFO: 172.29.0.5:45328 - "GET /ge_api/ArtistPerformance HTTP/1.1" 200 OK

But when running FastAPI behind the proxy, the ROOT_PATH is double before the endpoint which causes the query to be wrongly directed.

INFO: 172.29.0.9:45668 - "GET /ge_api/ge_api/ArtistPerformance HTTP/1.0" 404 Not Found

Here is FastAPI app config

app = FastAPI(
    root_path = "/ge_api",
    description = desc,
    openapi_tags = tags_metadata,
    version = "0.0.1",
    docs_url = '/ge_api/docs',
    redoc_url = '/ge_api/redoc',
    openapi_url = '/ge_api/openapi.json',
)

Nginx config:

location /ge_api {
			#proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
			#proxy_set_header X-Forwarded-Prefix /ge_api/api;
			#proxy_set_header Host $http_host;
			#proxy_http_version 1.1;
			proxy_pass http://ge_api:8080;	
		}

Is there any fixed for the issue? Thanks

@trungswat: I'm almost a year late on this, but the mistake you're making here is specifying /ge_api/docs for your ressource URLs, while root_path is automatically going to be prefixed to everything, so the final URL is something like root_path + docs_url == "/ge_api" + '/ge_api/docs'.