enhance: Prevent frequently updating metric

Signed-off-by: bigsheeper <[email protected]>

internal/querycoordv2/task/scheduler.go

@@ -168,6 +168,8 @@ type taskScheduler struct {
 	channelTasks map[replicaChannelIndex]Task
 	processQueue *taskQueue
 	waitQueue    *taskQueue
+
+	lastUpdateMetricTime time.Time
 }
 
 func NewScheduler(ctx context.Context,
@@ -280,13 +282,15 @@ func (scheduler *taskScheduler) Add(task Task) error {
 		scheduler.segmentTasks[index] = task
 	}
 
-	scheduler.updateTaskMetrics()
 	log.Ctx(task.Context()).Info("task added", zap.String("task", task.String()))
 	task.RecordStartTs()
 	return nil
 }
 
 func (scheduler *taskScheduler) updateTaskMetrics() {
+	if time.Since(scheduler.lastUpdateMetricTime) < 30*time.Second {
+		return
+	}
 	segmentGrowNum, segmentReduceNum, segmentMoveNum := 0, 0, 0
 	channelGrowNum, channelReduceNum, channelMoveNum := 0, 0, 0
 	for _, task := range scheduler.segmentTasks {
@@ -319,6 +323,7 @@ func (scheduler *taskScheduler) updateTaskMetrics() {
 	metrics.QueryCoordTaskNum.WithLabelValues(metrics.ChannelGrowTaskLabel).Set(float64(channelGrowNum))
 	metrics.QueryCoordTaskNum.WithLabelValues(metrics.ChannelReduceTaskLabel).Set(float64(channelReduceNum))
 	metrics.QueryCoordTaskNum.WithLabelValues(metrics.ChannelMoveTaskLabel).Set(float64(channelMoveNum))
+	scheduler.lastUpdateMetricTime = time.Now()
 }
 
 // check whether the task is valid to add,