FastAPI CORS Issue with External API Calls in Production Environment
I'm working on a project and hit a roadblock. I've looked through the documentation and I'm still confused about During development of a FastAPI application, I set up CORS to allow requests from my front-end hosted on a different domain... Everything works perfectly on localhost, but when I deploy the application, I encounter a `CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource` error. The specific configuration I have is as follows: ```python from fastapi import FastAPI from fastapi.middleware.cors import CORSMiddleware app = FastAPI() app.add_middleware( CORSMiddleware, allow_origins=["https://myfrontend.com"], # This is my production front-end domain allow_credentials=True, allow_methods=["GET", "POST", "OPTIONS"], allow_headers=["*"], ) ``` In my production environment, I’m running the FastAPI application behind an Nginx reverse proxy. The Nginx configuration includes: ```nginx server { listen 80; server_name api.mydomain.com; location / { proxy_pass http://localhost:8000; 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; } } ``` I’ve ensured that CORS is configured correctly in FastAPI, yet the browser still blocks the requests. I’ve also checked the network requests in Chrome and confirmed that the OPTIONS preflight request does return a response, but the main request fails. Any insights on what might be causing this discrepancy? Could it be related to Nginx settings or headers? Additionally, I tried adding the following headers to my Nginx configuration: ```nginx add_header 'Access-Control-Allow-Origin' '*'; add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS'; ``` However, this did not resolve the issue either. I'm keen to understand how to manage CORS effectively when integrating FastAPI with an external frontend in a production setup. Any help would be greatly appreciated! What's the best practice here? My development environment is CentOS. Cheers for any assistance!