Add support of heartbeat interval in "on change" subscription, so that

full sync would happen periodically when hb is triggered.

sonic_data_client/db_client.go

@@ -73,6 +73,10 @@ var Target2RedisDb = make(map[string]map[string]*redis.Client)
 // Any non-zero value that less than this threshold is considered invalid argument.
 var MinSampleInterval = time.Second
 
+// MinHeartbeatInterval is the lowest HB interval for streaming subscriptions.
+// This is reserved value, which should be adjusted per BGPL benchmark result.
+var MinHeartbeatInterval = 3 * time.Minute
+
 // IntervalTicker is a factory method to implement interval ticking.
 // Exposed for UT purposes.
 var IntervalTicker = func(interval time.Duration) <-chan time.Time {
@@ -212,7 +216,7 @@ func (c *DbClient) StreamRun(q *queue.PriorityQueue, stop chan struct{}, w *sync
 		for gnmiPath := range c.pathG2S {
 			c.w.Add(1)
 			c.synced.Add(1)
-			go streamOnChangeSubscription(c, gnmiPath)
+			go streamOnChangeSubscription(c, gnmiPath, nil)
 		}
 	} else {
 		log.V(2).Infof("Stream subscription request received, mode: %v, subscription count: %v",
@@ -230,7 +234,7 @@ func (c *DbClient) StreamRun(q *queue.PriorityQueue, stop chan struct{}, w *sync
 			} else if subMode == gnmipb.SubscriptionMode_ON_CHANGE {
 				c.w.Add(1)
 				c.synced.Add(1)
-				go streamOnChangeSubscription(c, sub.GetPath())
+				go streamOnChangeSubscription(c, nil, sub)
 			} else {
 				enqueueFatalMsg(c, fmt.Sprintf("unsupported subscription mode, %v", subMode))
 				return
@@ -255,19 +259,36 @@ func (c *DbClient) StreamRun(q *queue.PriorityQueue, stop chan struct{}, w *sync
 }
 
 // streamOnChangeSubscription implements Subscription "ON_CHANGE STREAM" mode
-func streamOnChangeSubscription(c *DbClient, gnmiPath *gnmipb.Path) {
+func streamOnChangeSubscription(c *DbClient, gnmiPath *gnmipb.Path, sub *gnmipb.Subscription) {
+	if gnmiPath == nil {
+		gnmiPath = sub.GetPath()
+	}
+
+	// if heartbeatInterval is not assigned, use 0 to ignore periodical full sync
+	var heartbeatInterval time.Duration = 0
+	if sub != nil {
+		var err error
+		heartbeatInterval, err = validateHeartbeatInterval(sub)
+		if err != nil {
+			enqueueFatalMsg(c, err.Error())
+			c.synced.Done()
+			c.w.Done()
+			return
+		}
+	}
+
 	tblPaths := c.pathG2S[gnmiPath]
 	log.V(2).Infof("streamOnChangeSubscription gnmiPath: %v", gnmiPath)
 
 	if tblPaths[0].field != "" {
 		if len(tblPaths) > 1 {
-			go dbFieldMultiSubscribe(c, gnmiPath, true, time.Millisecond*200, false)
+			go dbFieldMultiSubscribe(c, gnmiPath, true, heartbeatInterval, false)
 		} else {
-			go dbFieldSubscribe(c, gnmiPath, true, time.Millisecond*200)
+			go dbFieldSubscribe(c, gnmiPath, true, heartbeatInterval)
 		}
 	} else {
 		// sample interval and update only parameters are not applicable
-		go dbTableKeySubscribe(c, gnmiPath, 0, true)
+		go dbTableKeySubscribe(c, gnmiPath, heartbeatInterval, true)
 	}
 }
 
@@ -1340,3 +1361,17 @@ func validateSampleInterval(sub *gnmipb.Subscription) (time.Duration, error) {
 		return requestedInterval, nil
 	}
 }
+
+// validateHeartbeatInterval validates the heartbeat interval of the given subscription.
+func validateHeartbeatInterval(sub *gnmipb.Subscription) (time.Duration, error) {
+	requestedInterval := time.Duration(sub.GetHeartbeatInterval())
+	if requestedInterval == 0 {
+		// If the heartbeat_interval is set to 0, the target MUST create the subscription
+		// and send the data with the MinHeartbeatInterval
+		return MinHeartbeatInterval, nil
+	} else if requestedInterval < MinHeartbeatInterval {
+		return 0, fmt.Errorf("invalid heartbeat interval: %v. It cannot be less than %v", requestedInterval, MinHeartbeatInterval)
+	} else {
+		return requestedInterval, nil
+	}
+}