refactor updateTimestamp according to the comment

server/tso.go

@@ -82,30 +82,24 @@ func (s *Server) syncTimestamp() error {
 		return errors.Trace(err)
 	}
 
-	now := time.Now()
+	next := time.Now()
 	// If the current system time minus the saved etcd timestamp is less than updateTimestampGuard,
 	// the timestamp allocation will start from the saved etcd timestamp temporarily.
-	if subTimeByWallClock(now, last) < updateTimestampGuard {
-		log.Errorf("system time may be incorrect, last: %v, now: %v", last, now)
-		last = last.Add(updateTimestampGuard)
-		save := last.Add(s.cfg.TsoSaveInterval.Duration)
-		if err = s.saveTimestamp(save); err != nil {
-			return errors.Trace(err)
-		}
-		s.ts.Store(&atomicObject{physical: last})
-		return nil
+	if subTimeByWallClock(next, last) < updateTimestampGuard {
+		log.Errorf("system time may be incorrect: last: %v next %v", last, next)
+		next = next.Add(updateTimestampGuard)
 	}
 
-	save := now.Add(s.cfg.TsoSaveInterval.Duration)
+	save := next.Add(s.cfg.TsoSaveInterval.Duration)
 	if err = s.saveTimestamp(save); err != nil {
 		return errors.Trace(err)
 	}
 
 	tsoCounter.WithLabelValues("sync_ok").Inc()
-	log.Infof("sync and save timestamp: last %v save %v", last, save)
+	log.Infof("sync and save timestamp: last %v save %v next %v", last, save, next)
 
 	current := &atomicObject{
-		physical: now,
+		physical: next,
 	}
 	s.ts.Store(current)
 
@@ -118,76 +112,36 @@ func (s *Server) updateTimestamp() error {
 
 	tsoCounter.WithLabelValues("save").Inc()
 
-	since := subTimeByWallClock(now, prev.physical)
-	if since > 3*updateTimestampStep {
-		log.Warnf("clock offset: %v, prev: %v, now: %v", since, prev.physical, now)
+	jetLag := subTimeByWallClock(now, prev.physical)
+	if jetLag > 3*updateTimestampStep {
+		log.Warnf("clock offset: %v, prev: %v, now: %v", jetLag, prev.physical, now)
 		tsoCounter.WithLabelValues("slow_save").Inc()
 	}
 
-	// Check if the logical is still enough.
-	notEnough := atomic.LoadInt64(&prev.logical) > maxLogical/2
+	var next time.Time
+	if jetLag > updateTimestampGuard {
+		next = now
+	} else if atomic.LoadInt64(&prev.logical) > maxLogical/2 {
+		next = prev.physical.Add(time.Millisecond)
+	} else {
+		return nil
+	}
 
 	saved := s.lastSavedTime
-	// This is a normal situation.
-	if since > 0 {
-		// Avoid the same physical timestamp.
-		if since <= updateTimestampGuard {
-			tsoCounter.WithLabelValues("skip_save").Inc()
-			log.Warnf("invalid physical timestamp, prev: %v, now: %v, re-update later", prev.physical, now)
-			return nil
-		}
-		// If the time window is no more than updateTimestampGuard,
-		// it will adjust the time window.
-		if subTimeByWallClock(saved, now) <= updateTimestampGuard {
-			last := saved
-			save := now.Add(s.cfg.TsoSaveInterval.Duration)
-			if err := s.saveTimestamp(save); err != nil {
-				return errors.Trace(err)
-			}
-
-			tsoCounter.WithLabelValues("save_ok").Inc()
-			log.Debugf("save timestamp ok: prev %v last %v save %v", prev.physical, last, save)
-		} else {
-			if notEnough {
-				last := &atomicObject{
-					physical: now.Add(time.Millisecond),
-					logical:  0,
-				}
-				s.ts.Store(last)
-				return nil
-			}
-		}
-	} else {
-		if subTimeByWallClock(saved, prev.physical) <= updateTimestampGuard {
-			last := saved
-			save := prev.physical.Add(s.cfg.TsoSaveInterval.Duration)
-			if err := s.saveTimestamp(save); err != nil {
-				return errors.Trace(err)
-			}
-
-			tsoCounter.WithLabelValues("save_incorrect").Inc()
-			log.Debugf("save timestamp incorrect: now %v prev %v last %v save %v", now, prev.physical, last, save)
-		} else {
-			if notEnough {
-				last := &atomicObject{
-					physical: prev.physical.Add(time.Millisecond),
-					logical:  0,
-				}
-				s.ts.Store(last)
-				return nil
-			}
+	if subTimeByWallClock(saved, next) <= updateTimestampGuard {
+		save := next.Add(s.cfg.TsoSaveInterval.Duration)
+		if err := s.saveTimestamp(save); err != nil {
+			return errors.Trace(err)
 		}
-		// Since the physical timestamp is greater than the current system time,
-		// the physical timestamp will be used to alloc timestamp temporarily.
-		return nil
 	}
 
 	current := &atomicObject{
-		physical: now,
+		physical: next,
+		logical:  0,
 	}
 
 	s.ts.Store(current)
-	metadataGauge.WithLabelValues("tso").Set(float64(current.physical.Unix()))
+	metadataGauge.WithLabelValues("tso").Set(float64(next.Unix()))
 
 	return nil
 }
@@ -206,7 +160,6 @@ func (s *Server) getRespTS(count uint32) (pdpb.Timestamp, error) {
 
 		resp.Physical = current.physical.UnixNano() / int64(time.Millisecond)
 		resp.Logical = atomic.AddInt64(&current.logical, int64(count))
-
 		if resp.Logical >= maxLogical {
 			log.Errorf("logical part outside of max logical interval %v, please check ntp time, retry count %d", resp, i)
 			time.Sleep(updateTimestampStep)