events {
    worker_connections 1024;
}

http {
    upstream node_app {
        ip_hash;  # Enables session persistence based on client IP
        server node-app-1:4000;
        server node-app-2:4000;
        server node-app-3:4000;
    }

    # WebSocket upgrade configuration
    map $http_upgrade $connection_upgrade {
        default upgrade;
        ''      close;
    }

    server {
        listen 80;
        
        location / {
            proxy_pass http://node_app;
            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;
            
            # WebSocket headers
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection $connection_upgrade;
            proxy_read_timeout 86400;  # Keep WebSocket connections alive (24 hours)
        }

        # Health check endpoint
        location /health {
            proxy_pass http://node_app;
            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;
        }
    }
}