fix websocket concurrent write

addon/web/web.go

@@ -41,6 +41,11 @@ func (web *WebAddon) echo(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+type concurrentConn struct {
+	conn *websocket.Conn
+	mu   sync.Mutex
+}
+
 type WebAddon struct {
 	addon.Base
 	addr      string
@@ -48,7 +53,7 @@ type WebAddon struct {
 	serverMux *http.ServeMux
 	server    *http.Server
 
-	conns   []*websocket.Conn
+	conns   []*concurrentConn
 	connsMu sync.RWMutex
 }
 
@@ -79,7 +84,7 @@ func NewWebAddon() *WebAddon {
 
 	web.server = &http.Server{Addr: web.addr, Handler: web.serverMux}
 	log = log.WithField("in", "WebAddon")
-	web.conns = make([]*websocket.Conn, 0)
+	web.conns = make([]*concurrentConn, 0)
 
 	go func() {
 		log.Infof("server start listen at %v\n", web.addr)
@@ -92,7 +97,7 @@ func NewWebAddon() *WebAddon {
 
 func (web *WebAddon) addConn(c *websocket.Conn) {
 	web.connsMu.Lock()
-	web.conns = append(web.conns, c)
+	web.conns = append(web.conns, &concurrentConn{conn: c})
 	web.connsMu.Unlock()
 }
 
@@ -102,7 +107,7 @@ func (web *WebAddon) removeConn(conn *websocket.Conn) {
 
 	index := -1
 	for i, c := range web.conns {
-		if conn == c {
+		if conn == c.conn {
 			index = i
 			break
 		}
@@ -130,7 +135,9 @@ func (web *WebAddon) sendFlow(on string, f *flow.Flow) {
 		return
 	}
 	for _, c := range conns {
-		c.WriteMessage(websocket.TextMessage, b)
+		c.mu.Lock()
+		c.conn.WriteMessage(websocket.TextMessage, b)
+		c.mu.Unlock()
 	}
 }