Emit scale down metric even when there is no scale down candidates

Author: jackfrancis

cluster-autoscaler/core/scaledown/status/status.go

@@ -100,6 +100,8 @@ const (
 	ScaleDownInCooldown
 	// ScaleDownInProgress - the scale down wasn't attempted, because a previous scale-down was still in progress.
 	ScaleDownInProgress
+	// ScaleDownNoCandidates - the scale down was skipped because of no scale down candidates.
+	ScaleDownNoCandidates
 )
 
 // NodeDeleteResultType denotes the type of the result of node deletion. It provides deeper

cluster-autoscaler/core/static_autoscaler.go

@@ -626,7 +626,7 @@ func (a *StaticAutoscaler) RunOnce(currentTime time.Time) caerrors.AutoscalerErr
 
 		metrics.UpdateDurationFromStart(metrics.FindUnneeded, unneededStart)
 
-		scaleDownInCooldown := a.isScaleDownInCooldown(currentTime, scaleDownCandidates)
+		scaleDownInCooldown := a.isScaleDownInCooldown(currentTime)
 		klog.V(4).Infof("Scale down status: lastScaleUpTime=%s lastScaleDownDeleteTime=%v "+
 			"lastScaleDownFailTime=%s scaleDownForbidden=%v scaleDownInCooldown=%v",
 			a.lastScaleUpTime, a.lastScaleDownDeleteTime, a.lastScaleDownFailTime,
@@ -703,8 +703,8 @@ func (a *StaticAutoscaler) updateSoftDeletionTaints(allNodes []*apiv1.Node) {
 	}
 }
 
-func (a *StaticAutoscaler) isScaleDownInCooldown(currentTime time.Time, scaleDownCandidates []*apiv1.Node) bool {
-	scaleDownInCooldown := a.processorCallbacks.disableScaleDownForLoop || len(scaleDownCandidates) == 0
+func (a *StaticAutoscaler) isScaleDownInCooldown(currentTime time.Time) bool {
+	scaleDownInCooldown := a.processorCallbacks.disableScaleDownForLoop
 
 	if a.ScaleDownDelayTypeLocal {
 		return scaleDownInCooldown

cluster-autoscaler/core/static_autoscaler_test.go

@@ -2599,28 +2599,35 @@ func TestCleaningSoftTaintsInScaleDown(t *testing.T) {
 	tests := []struct {
 		name                          string
 		testNodes                     []*apiv1.Node
-		expectedScaleDownCoolDown     bool
+		scaleDownInCoolDown           bool
 		expectedNodesWithSoftTaints   []*apiv1.Node
 		expectedNodesWithNoSoftTaints []*apiv1.Node
 	}{
 		{
-			name:                          "Soft tainted nodes are cleaned in case of scale down is in cool down",
+			name:                          "Soft tainted nodes are cleaned when scale down skipped",
 			testNodes:                     nodesToHaveNoTaints,
-			expectedScaleDownCoolDown:     true,
+			scaleDownInCoolDown:           false,
 			expectedNodesWithSoftTaints:   []*apiv1.Node{},
 			expectedNodesWithNoSoftTaints: nodesToHaveNoTaints,
 		},
 		{
-			name:                          "Soft tainted nodes are not cleaned in case of scale down isn't in cool down",
+			name:                          "Soft tainted nodes are cleaned when scale down in cooldown",
+			testNodes:                     nodesToHaveNoTaints,
+			scaleDownInCoolDown:           true,
+			expectedNodesWithSoftTaints:   []*apiv1.Node{},
+			expectedNodesWithNoSoftTaints: nodesToHaveNoTaints,
+		},
+		{
+			name:                          "Soft tainted nodes are not cleaned when scale down requested",
 			testNodes:                     nodesToHaveTaints,
-			expectedScaleDownCoolDown:     false,
+			scaleDownInCoolDown:           false,
 			expectedNodesWithSoftTaints:   nodesToHaveTaints,
 			expectedNodesWithNoSoftTaints: []*apiv1.Node{},
 		},
 		{
-			name:                          "Soft tainted nodes are cleaned only from min sized node group in case of scale down isn't in cool down",
+			name:                          "Soft tainted nodes are cleaned only from min sized node group when scale down requested",
 			testNodes:                     append(nodesToHaveNoTaints, nodesToHaveTaints...),
-			expectedScaleDownCoolDown:     false,
+			scaleDownInCoolDown:           false,
 			expectedNodesWithSoftTaints:   nodesToHaveTaints,
 			expectedNodesWithNoSoftTaints: nodesToHaveNoTaints,
 		},
@@ -2631,12 +2638,12 @@ func TestCleaningSoftTaintsInScaleDown(t *testing.T) {
 			fakeClient := buildFakeClient(t, test.testNodes...)
 
 			autoscaler := buildStaticAutoscaler(t, provider, test.testNodes, test.testNodes, fakeClient)
+			autoscaler.processorCallbacks.disableScaleDownForLoop = test.scaleDownInCoolDown
+			assert.Equal(t, autoscaler.isScaleDownInCooldown(time.Now()), test.scaleDownInCoolDown)
 
 			err := autoscaler.RunOnce(time.Now())
 
 			assert.NoError(t, err)
-			candidates, _ := autoscaler.processors.ScaleDownNodeProcessor.GetScaleDownCandidates(autoscaler.AutoscalingContext, test.testNodes)
-			assert.Equal(t, test.expectedScaleDownCoolDown, autoscaler.isScaleDownInCooldown(time.Now(), candidates))
 
 			assertNodesSoftTaintsStatus(t, fakeClient, test.expectedNodesWithSoftTaints, true)
 			assertNodesSoftTaintsStatus(t, fakeClient, test.expectedNodesWithNoSoftTaints, false)