Support mounting application elsewhere than at root path

[Tronic]

Sanic app might be exposed publicly in a path other than root at a HTTP server that also serves other things on the same domain. E.g. https://company.com/blog/ is proxied to Sanic app at http://localhost:8000/.

Currently Sanic offers no support for that, with url_for resolving to absolute paths pointing at site root.

It would be good to add support e.g. via config.SERVER_NAME that also included the external root path, so that proper URLs would be formed whenever external URLs are requested. The path information is already available but not used if presented on proxy headers req.forwarded, whereas I am not exactly sure of SERVER_NAME handling.

[sjsadowski]

I like this idea.

[ahopkins]

This seems like a fairly easy one to add.

[ahopkins]

Related discussion: https://community.sanicframework.org/t/sanic-app-on-nginx-subpath/463

[ahopkins]

I finally got back to testing this. I ran the following on:

• 19.12LTS
• 20.12LTS
• master
• sanic-routing

On all of these branches, this seemed to work fine.

from sanic import Sanic
from sanic.response import text

app = Sanic("app")
app.config.SERVER_NAME = "example.com/api"


@app.route("/foo")
def handler(request):
    url = app.url_for("handler", _external=True)
    return text(f"URL: {url}")

The result:

URL: http://example.com/api/foo

Am I missing something? Can we close this?

[ashleysommer]

Yep, that's right. I deploy sanic using that same pattern at my workplace in several applications.
I agree there could be a slightly more elegant way of doing it, but using config.SERVER_NAME is easy and just works (as long as you remember to always pass _external=True to url_for())
Maybe it could be documented better?

[ahopkins]

Marking as a documentation issue.

[ahopkins]

Documented in this PR