Unexpected 502 Bad Gateway scenarios with FastAPI and Nginx on Deployment
I'm stuck on something that should probably be simple. I've been struggling with this for a few days now and could really use some help. I'm deploying a FastAPI application using Uvicorn and Nginx, but I'm working with a `502 Bad Gateway` behavior when I try to access the app in the browser. Locally, everything works perfectly; I can run the app using `uvicorn main:app --host 0.0.0.0 --port 8000` and access it at `http://localhost:8000`. However, once I set it up with Nginx on my server, it fails. Here's my Nginx configuration: ```nginx server { listen 80; server_name myapp.com; location / { proxy_pass http://127.0.0.1:8000; 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 made sure that Uvicorn is running on port 8000 and that there are no firewall rules blocking it. When I check the Nginx behavior log, I find entries like this: ``` 2023/10/01 12:00:00 [behavior] 12345#12345: *1 connect() failed (111: Connection refused) while connecting to upstream, client: 192.168.1.1, server: myapp.com, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:8000/", host: "myapp.com" ``` I've tried restarting both Uvicorn and Nginx, and I even changed the `proxy_pass` URL to `http://localhost:8000` to see if that makes a difference, but the scenario continues. Could it be a question with how Uvicorn is configured to run in the background, or is there something wrong with my Nginx configuration? Any suggestions for debugging this would be greatly appreciated. I'd really appreciate any guidance on this. My development environment is Linux.