Same Origin Policy violated on localhost with falcon webserver

问题

I am running an elm frontend via elm-reactor on localhost:8000. It is supposed to load json files from a falcon backend running via gunicorn on localhost:8010. This fails.

The frontend is able to load static dummy files served by elm-reactor (:8000) but when I try to replace the dummies by the actual backend (:8010) it fails due to a missing header:

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost:8010/api/sheets. (Reason: CORS header 'Access-Control-Allow-Origin' missing).

The error message from the Firefox Inspector seems reasonably clear, but I'm at a loss how to fix that. I already installed a CORS middleware in falcon, but that didn't improve the situation at all.

from falcon_cors import CORS
cors = CORS(allow_origins_list=['*'])
api = falcon.API(middleware=[cors.middleware])

I did also try to use the origins 'localhost:8000' and 'localhost' but neither works.

Any idea how to fix this?

回答1:

Try this. Hopefully, this will solve your problem.

import falcon
from falcon_cors import CORS
cors = CORS(allow_origins_list=['http://localhost:8080', 'http://localhost:8000', 'http://localhost:8010'], allow_all_headers=True, allow_methods_list=['GET', 'POST', 'OPTIONS'])
api = falcon.API(middleware=[cors.middleware])

回答2:

It turns out that falcon_cors offers allow_all_origins=True as a parameter. This fixes my problem, but isn't a perfect solution.

When using POST requests as well allow_all_methods=True should be set as well.

来源：https://stackoverflow.com/questions/39546536/same-origin-policy-violated-on-localhost-with-falcon-webserver