Engineering Million-Connection WebSocket Infrastructure in Go: Zero-Memory-Copy Event Broadcasting

package main

import (
	"sync"
	"time"
	"github.com/gobwas/ws"
	"github.com/gobwas/ws/wsutil"
)

// Zero-allocation buffer pool to eliminate GC pressure
var bufferPool = sync.Pool{
	New: func() interface{} {
		b := make([]byte, 4096)
		return &b
	},
}

type ClientConnection struct {
	fd   int
	send chan []byte
}

type BroadcastHub struct {
	clients    map[*ClientConnection]bool
	broadcast  chan []byte
	register   chan *ClientConnection
	unregister chan *ClientConnection
	mu         sync.RWMutex
}

func (h *BroadcastHub) Run() {
	for {
		select {
		case client := <-h.register:
			h.mu.Lock()
			h.clients[client] = true
			h.mu.Unlock()
		case client := <-h.unregister:
			h.mu.Lock()
			if _, ok := h.clients[client]; ok {
				delete(h.clients, client)
				close(client.send)
			}
			h.mu.Unlock()
		case message := <-h.broadcast:
			h.mu.RLock()
			for client := range h.clients {
				select {
				case client.send <- message:
				default:
					// Drop slow consumer connections to prevent pipeline backpressure
					close(client.send)
					delete(h.clients, client)
				}
			}
			h.mu.RUnlock()
		}
	}
}