maps: Consider actual passed time for GC interval calculation

When GetInterval calculates the new GC interval, it uses the result of
the previous calculation as a pivot point. However, if GC was triggered
by a signal, smaller time interval has passed, therefore, expectations
on the delete ratio should be lower. Adjust the delete ratio
proportionally to avoid increasing the interval uncontrollably when
multiple signals arrive over a short period of time.

Ref: #27405
Signed-off-by: Maxim Mikityanskiy <maxim@isovalent.com>

pkg/maps/ctmap/ctmap.go

@@ -864,25 +864,31 @@ var cachedGCInterval time.Duration
 
 // GetInterval returns the interval adjusted based on the deletion ratio of the
 // last run
-func GetInterval(maxDeleteRatio float64) time.Duration {
+func GetInterval(actualPrevInterval time.Duration, maxDeleteRatio float64) time.Duration {
 	if val := option.Config.ConntrackGCInterval; val != time.Duration(0) {
 		return val
 	}
 
-	prevInterval := cachedGCInterval
-	if prevInterval == time.Duration(0) {
-		prevInterval = defaults.ConntrackGCStartingInterval
+	expectedPrevInterval := cachedGCInterval
+	adjustedDeleteRatio := maxDeleteRatio
+	if expectedPrevInterval == time.Duration(0) {
+		expectedPrevInterval = defaults.ConntrackGCStartingInterval
+	} else if actualPrevInterval < expectedPrevInterval && actualPrevInterval > 0 {
+		adjustedDeleteRatio *= float64(expectedPrevInterval) / float64(actualPrevInterval)
 	}
 
-	newInterval := calculateInterval(prevInterval, maxDeleteRatio)
+	newInterval := calculateInterval(expectedPrevInterval, adjustedDeleteRatio)
 	if val := option.Config.ConntrackGCMaxInterval; val != time.Duration(0) && newInterval > val {
 		newInterval = val
 	}
 
-	if newInterval != prevInterval {
+	if newInterval != expectedPrevInterval {
 		log.WithFields(logrus.Fields{
-			"newInterval": newInterval,
-			"deleteRatio": maxDeleteRatio,
+			"expectedPrevInterval": expectedPrevInterval,
+			"actualPrevInterval":   actualPrevInterval,
+			"newInterval":          newInterval,
+			"deleteRatio":          maxDeleteRatio,
+			"adjustedDeleteRatio":  adjustedDeleteRatio,
 		}).Info("Conntrack garbage collector interval recalculated")
 	}
 

pkg/maps/ctmap/ctmap_test.go

@@ -46,21 +46,21 @@ func (t *CTMapTestSuite) TestCalculateInterval(c *C) {
 
 func (t *CTMapTestSuite) TestGetInterval(c *C) {
 	cachedGCInterval = time.Minute
-	c.Assert(GetInterval(0.1), Equals, time.Minute)
+	c.Assert(GetInterval(cachedGCInterval, 0.1), Equals, time.Minute)
 
 	// Setting ConntrackGCInterval overrides the calculation
 	oldInterval := option.Config.ConntrackGCInterval
 	option.Config.ConntrackGCInterval = 10 * time.Second
-	c.Assert(GetInterval(0.1), Equals, 10*time.Second)
+	c.Assert(GetInterval(cachedGCInterval, 0.1), Equals, 10*time.Second)
 	option.Config.ConntrackGCInterval = oldInterval
-	c.Assert(GetInterval(0.1), Equals, time.Minute)
+	c.Assert(GetInterval(cachedGCInterval, 0.1), Equals, time.Minute)
 
 	// Setting ConntrackGCMaxInterval limits the maximum interval
 	oldMaxInterval := option.Config.ConntrackGCMaxInterval
 	option.Config.ConntrackGCMaxInterval = 20 * time.Second
-	c.Assert(GetInterval(0.1), Equals, 20*time.Second)
+	c.Assert(GetInterval(cachedGCInterval, 0.1), Equals, 20*time.Second)
 	option.Config.ConntrackGCMaxInterval = oldMaxInterval
-	c.Assert(GetInterval(0.1), Equals, time.Minute)
+	c.Assert(GetInterval(cachedGCInterval, 0.1), Equals, time.Minute)
 
 	cachedGCInterval = time.Duration(0)
 }

pkg/maps/ctmap/gc/gc.go

@@ -101,6 +101,7 @@ func (gc *GC) Enable(restoredEndpoints []*endpoint.Endpoint) {
 		ipv6 := gc.ipv6
 		triggeredBySignal := false
 		ctTimer, ctTimerDone := inctimer.New()
+		var gcPrev time.Time
 		defer ctTimerDone()
 		for {
 			var (
@@ -138,6 +139,12 @@ func (gc *GC) Enable(restoredEndpoints []*endpoint.Endpoint) {
 				}
 			)
 
+			gcInterval := gcStart.Sub(gcPrev)
+			if gcPrev.IsZero() {
+				gcInterval = time.Duration(0)
+			}
+			gcPrev = gcStart
+
 			eps := gc.endpointsManager.GetEndpoints()
 			for _, e := range eps {
 				epsMap[e.IPv4Address()] = e
@@ -190,7 +197,7 @@ func (gc *GC) Enable(restoredEndpoints []*endpoint.Endpoint) {
 						ipv6 = true
 					}
 				}
-			case <-ctTimer.After(ctmap.GetInterval(maxDeleteRatio)):
+			case <-ctTimer.After(ctmap.GetInterval(gcInterval, maxDeleteRatio)):
 				gc.signalHandler.MuteSignals()
 				ipv4 = gc.ipv4
 				ipv6 = gc.ipv6