feat: implement real-time Pub/Sub alert broadcast system and update docs/GRPC.md

lib/grpcentity/server.go

@@ -31,6 +31,28 @@ var (
 	storeMu   sync.RWMutex
 )
 
+type AlertSubscriber struct {
+	ClientId string
+	Channel  chan *protoapi.AlertMessage
+}
+
+var (
+	subscribers = make(map[string]*AlertSubscriber)
+	subMu       sync.Mutex
+)
+
+func publishAlert(alert *protoapi.AlertMessage) {
+	subMu.Lock()
+	defer subMu.Unlock()
+	for _, sub := range subscribers {
+		select {
+		case sub.Channel <- alert:
+		default:
+			fmt.Printf("Alert channel blocked for client %s, dropping event\n", sub.ClientId)
+		}
+	}
+}
+
 func random(min, max int, src rand.Source) int {
 	return rand.New(src).Intn(max-min) + min
 }
@@ -81,6 +103,17 @@ func (IoTServer) GetDate(ctx context.Context, r *protoapi.RequestDateTime) (*pro
 func (IoTServer) UpdateSensingData(ctx context.Context, r *protoapi.SensingData) (*protoapi.SensingResponse, error) {
 	fmt.Printf("Received sensing data - Device: %s, Temp: %.2f°C, Humid: %.2f%%\n", r.GetDeviceId(), r.GetTemperature(), r.GetHumidity())
 
+	// 임계값 초과(40도 초과) 시 실시간 Pub/Sub 경보 메시지 발행
+	if r.GetTemperature() > 40.0 {
+		fmt.Printf("⚠️ Critical temperature detected: %.2f°C! Publishing warning...\n", r.GetTemperature())
+		publishAlert(&protoapi.AlertMessage{
+			AlertId:   fmt.Sprintf("alert-%d", time.Now().UnixNano()),
+			DeviceId:  r.GetDeviceId(),
+			Message:   fmt.Sprintf("Critical high temperature: %.2f°C (Humidity: %.2f%%)", r.GetTemperature(), r.GetHumidity()),
+			Timestamp: time.Now().Unix(),
+		})
+	}
+
 	response := &protoapi.SensingResponse{
 		Success: true,
 		Message: fmt.Sprintf("Sensing data updated successfully for device %s", r.GetDeviceId()),
@@ -185,6 +218,41 @@ func (IoTServer) DownloadFile(r *protoapi.DownloadRequest, stream protoapi.IoTSe
 	return nil
 }
 
+func (IoTServer) SubscribeAlerts(r *protoapi.AlertSubscription, stream protoapi.IoTService_SubscribeAlertsServer) error {
+	clientId := r.GetClientId()
+	ch := make(chan *protoapi.AlertMessage, 10)
+	sub := &AlertSubscriber{
+		ClientId: clientId,
+		Channel:  ch,
+	}
+
+	subMu.Lock()
+	subscribers[clientId] = sub
+	subMu.Unlock()
+
+	fmt.Printf("Client %s subscribed to alerts on topic '%s'\n", clientId, r.GetTopic())
+
+	for {
+		select {
+		case alert := <-ch:
+			err := stream.Send(alert)
+			if err != nil {
+				subMu.Lock()
+				delete(subscribers, clientId)
+				subMu.Unlock()
+				fmt.Printf("Client %s alert subscription disconnected: %v\n", clientId, err)
+				return err
+			}
+		case <-stream.Context().Done():
+			subMu.Lock()
+			delete(subscribers, clientId)
+			subMu.Unlock()
+			fmt.Printf("Client %s unsubscribed (context done)\n", clientId)
+			return nil
+		}
+	}
+}
+
 func ServerRun(addr string) {
 	server := grpc.NewServer()
 	var iotServer IoTServer