nginx.conf

# This directive sets the number of worker processes to automatically adjust based on the number of CPU cores available.
# This is useful for optimizing performance without manually specifying the number of processes.
worker_processes auto;

# This directive sets the maximum number of open file descriptors for each worker process.
# Increasing this limit can help handle a large number of simultaneous connections.
worker_rlimit_nofile 500000;

events {
    # This tells Nginx to use the epoll method for managing connections on Linux.
    # epoll is efficient for handling a large number of simultaneous connections.
    # More options here: https://nginx.org/en/docs/events.html
    use epoll;

    # This sets the maximum number of connections that each worker process can handle.
    # A higher number allows more simultaneous connections.
    # More about here: https://www.nginx.com/blog/tuning-nginx/
    worker_connections 1024;
}

http {
    # This disables the access log, which can improve performance by not writing every request to a log file.
    access_log off;

    # This redirects error logs to /dev/null, effectively discarding them, except for emergency level messages.
    # This can be risky but may improve performance by avoiding disk writes for errors.
    error_log /dev/null emerg;

    upstream api {
        # These lines define a group of servers that can handle requests to the api upstream.
        # Requests will be load-balanced between these servers.
        server 127.0.0.1:8080;
        server 127.0.0.1:8081;

        # Sets the number of idle keepalive connections to upstream servers that are preserved.
        # This can improve performance by reusing connections for multiple requests.
        keepalive 250;
    }

    server {
        # Configures the server to listen on port 9999 for incoming connections.
        listen 9999;

        # This block defines how to respond to requests for the root URL (/).
        # Inside this block, several directives configure how to proxy these requests to the upstream api
        location / {
            # Disables buffering of responses from the proxied server, which can reduce latency for streaming or real-time applications.
            proxy_buffering off;

            # Clears the Connection header before forwarding the request to the proxied server.
            proxy_set_header Connection "";

            # Sets the HTTP version to 1.1 for requests to the proxied server.
            proxy_http_version 1.1;

            # Clears the Keep-Alive header before forwarding the request.
            proxy_set_header Keep-Alive "";

            # Sets the Proxy-Connection header to keep-alive to maintain a persistent connection to the proxied server.
            proxy_set_header Proxy-Connection "keep-alive";

            # Specifies that the request should be forwarded to the api upstream group defined earlier.
            proxy_pass http://api;
        }
    }
}