From 8747cd81f96da82721089c90f3d93ea5a00b40f8 Mon Sep 17 00:00:00 2001
From: Ralph Slooten <axllent@gmail.com>
Date: Thu, 11 Jun 2026 20:09:42 +1200
Subject: [PATCH] Chore:  Compress websocket messages once per broadcast to
 improve performance (#695)

---
 server/websockets/client.go | 6 +++---
 server/websockets/hub.go    | 8 +++++++-
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/server/websockets/client.go b/server/websockets/client.go
index 1fca11f..a7ef0cf 100644
--- a/server/websockets/client.go
+++ b/server/websockets/client.go
@@ -47,7 +47,7 @@ type Client struct {
 	conn *websocket.Conn
 
 	// Buffered channel of outbound messages.
-	send chan []byte
+	send chan *websocket.PreparedMessage
 }
 
 // ReadPump is used here solely to monitor the connection, not to actually receive messages.
@@ -90,7 +90,7 @@ func (c *Client) writePump() {
 				return
 			}
 
-			if err := c.conn.WriteMessage(websocket.TextMessage, message); err != nil {
+			if err := c.conn.WritePreparedMessage(message); err != nil {
 				return
 			}
 		case <-ticker.C:
@@ -124,7 +124,7 @@ func ServeWs(hub *Hub, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	client := &Client{hub: hub, conn: conn, send: make(chan []byte, 256)}
+	client := &Client{hub: hub, conn: conn, send: make(chan *websocket.PreparedMessage, 256)}
 	client.hub.register <- client
 
 	// Allow collection of memory referenced by the caller by doing all work in new goroutines.
diff --git a/server/websockets/hub.go b/server/websockets/hub.go
index 266ab5e..a3f8b49 100644
--- a/server/websockets/hub.go
+++ b/server/websockets/hub.go
@@ -6,6 +6,7 @@ import (
 	"sync/atomic"
 
 	"github.com/axllent/mailpit/internal/logger"
+	"github.com/gorilla/websocket"
 )
 
 // Hub maintains the set of active clients and broadcasts messages to the
@@ -61,9 +62,14 @@ func (h *Hub) Run() {
 				h.clientCount.Add(-1)
 			}
 		case message := <-h.Broadcast:
+			prepared, err := websocket.NewPreparedMessage(websocket.TextMessage, message)
+			if err != nil {
+				logger.Log().Errorf("[websocket] error preparing message: %s", err.Error())
+				continue
+			}
 			for client := range h.Clients {
 				select {
-				case client.send <- message:
+				case client.send <- prepared:
 				default:
 					close(client.send)
 					delete(h.Clients, client)