Nginx proxy configuration for FastAPI with WebSockets

# /etc/nginx/conf.d/default.conf

# Shared proxy settings
map $http_upgrade $connection_upgrade {
    default upgrade;
    '' close;
}

upstream fastapi_backend {
    server api:8000;  # Docker service name
    keepalive 32;     # Persistent connections to upstream
}

server {
    listen 80;
    server_name api.example.com;

    # Redirect HTTP to HTTPS
    return 301 https://$host$request_uri;
}

server {
    listen 443 ssl;
    server_name api.example.com;

    ssl_certificate /etc/letsencrypt/live/api.example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/api.example.com/privkey.pem;

    # Regular HTTP API
    location /api/ {
        proxy_pass http://fastapi_backend;
        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;
        proxy_http_version 1.1;
        proxy_read_timeout 30s;
    }

    # WebSocket endpoint
    location /ws/ {
        proxy_pass http://fastapi_backend;
        proxy_http_version 1.1;
        # Critical: these headers enable WebSocket upgrade
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection $connection_upgrade;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        # Longer timeout for persistent WebSocket connections
        proxy_read_timeout 3600s;
        proxy_send_timeout 3600s;
    }

    # Server-Sent Events
    location /events/ {
        proxy_pass http://fastapi_backend;
        proxy_http_version 1.1;
        proxy_set_header Connection '';
        proxy_cache off;
        proxy_buffering off;  # Critical: disable buffering for SSE
        proxy_read_timeout 3600s;
        add_header X-Accel-Buffering no;
    }
}