add log for unexpected jitter (#2752)

pkg/sfu/forwardstats.go

@@ -1,11 +1,13 @@
 package sfu
 
 import (
+	"fmt"
 	"sync"
 	"sync/atomic"
 	"time"
 
 	"github.com/livekit/livekit-server/pkg/telemetry/prometheus"
+	"github.com/livekit/protocol/logger"
 	"github.com/livekit/protocol/utils"
 )
 
@@ -46,9 +48,17 @@ func (s *ForwardStats) Update(arrival, left time.Time) {
 
 func (s *ForwardStats) GetStats() (latency, jitter time.Duration) {
 	s.lock.Lock()
-	defer s.lock.Unlock()
 	w := s.latency.Summarize()
-	return time.Duration(w.Mean()), time.Duration(w.StdDev())
+	s.lock.Unlock()
+	latency, jitter = time.Duration(w.Mean()), time.Duration(w.StdDev())
+	// TODO: remove this check after debugging unexpected jitter issue
+	if jitter > 10*time.Second {
+		logger.Infow("unexpected forward jitter",
+			"jitter", jitter,
+			"stats", fmt.Sprintf("count %.2f, mean %.2f, stdDev %.2f", w.Count(), w.Mean(), w.StdDev()),
+		)
+	}
+	return
 }
 
 func (s *ForwardStats) GetLastStats(duration time.Duration) (latency, jitter time.Duration) {