Take into account the revisionTimeout field instead of the progressDe…

…adline

also added a condition in the Scale function in which in case we are not
receiving data, check if you had panicked and the stable windows has passed,
and continue to check again further conditions

pkg/autoscaler/scaling/autoscaler.go

@@ -169,7 +169,13 @@ func (a *autoscaler) Scale(logger *zap.SugaredLogger, now time.Time) ScaleResult
 		} else {
 			logger.Errorw("Failed to obtain metrics", zap.Error(err))
 		}
-		return invalidSR
+		if errors.Is(err, metrics.ErrNoData) && !a.panicTime.IsZero() && a.panicTime.Add(spec.StableWindow).Before(now) {
+			// We are not receiving data, but we panicked before, and the panic stable window has gone, we want to continue.
+			// We want to un-panic and scale down to 0 if the rest of the conditions allow it
+			logger.Debug("No data to scale on yet, and panicked before, but the stable window has gone, we want to continue")
+		} else {
+			return invalidSR
+		}
 	}
 
 	// Make sure we don't get stuck with the same number of pods, if the scale up rate

pkg/reconciler/autoscaling/kpa/scaler.go

@@ -19,6 +19,7 @@ package kpa
 import (
 	"context"
 	"fmt"
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"net/http"
 	"time"
 
@@ -187,7 +188,9 @@ func (ks *scaler) handleScaleToZero(ctx context.Context, pa *autoscalingv1alpha1
 	}
 	cfgD := cfgs.Deployment
 	var activationTimeout time.Duration
-	if progressDeadline, ok := pa.ProgressDeadline(); ok {
+	if revTimeout, err := ks.revisionTimeout(ctx, pa); err == nil && revTimeout > 0 {
+		activationTimeout = time.Duration(revTimeout) * time.Second
+	} else if progressDeadline, ok := pa.ProgressDeadline(); ok {
 		activationTimeout = progressDeadline + activationTimeoutBuffer
 	} else {
 		activationTimeout = cfgD.ProgressDeadline + activationTimeoutBuffer
@@ -325,7 +328,6 @@ func (ks *scaler) applyScale(ctx context.Context, pa *autoscalingv1alpha1.PodAut
 func (ks *scaler) scale(ctx context.Context, pa *autoscalingv1alpha1.PodAutoscaler, sks *netv1alpha1.ServerlessService, desiredScale int32) (int32, error) {
 	asConfig := config.FromContext(ctx).Autoscaler
 	logger := logging.FromContext(ctx)
-
 	if desiredScale < 0 && !pa.Status.IsActivating() {
 		logger.Debug("Metrics are not yet being collected.")
 		return desiredScale, nil
@@ -370,3 +372,20 @@ func (ks *scaler) scale(ctx context.Context, pa *autoscalingv1alpha1.PodAutoscal
 	logger.Infof("Scaling from %d to %d", currentScale, desiredScale)
 	return desiredScale, ks.applyScale(ctx, pa, desiredScale, ps)
 }
+func (ks *scaler) revisionTimeout(ctx context.Context, pa *autoscalingv1alpha1.PodAutoscaler) (int64, error) {
+	gvr := schema.GroupVersionResource{
+		Group:    "serving.knative.dev",
+		Version:  "v1",
+		Resource: "revisions",
+	}
+	uRevision, err := ks.dynamicClient.Resource(gvr).Namespace(pa.Namespace).Get(ctx, pa.Name, metav1.GetOptions{})
+	if err == nil {
+		var timeoutSeconds interface{}
+		var found bool
+		timeoutSeconds, found, err = unstructured.NestedFieldNoCopy(uRevision.Object, "spec", "timeoutSeconds")
+		if err == nil && found {
+			return timeoutSeconds.(int64), nil
+		}
+	}
+	return -1, err
+}