Reintroduce the cache of instances known not to be owned by any ASG

This now needs to be invalidated whenever we register a new ASG, as that
ASG may include instances that we previously cached as unowned.

cluster-autoscaler/cloudprovider/aws/auto_scaling_groups.go

@@ -33,6 +33,7 @@ const scaleToZeroSupported = false
 type autoScalingGroups struct {
 	registeredAsgs      []*asgInformation
 	instanceToAsg       map[AwsRef]*Asg
+	notInRegisteredAsg  map[AwsRef]bool
 	registeredAsgsMutex sync.RWMutex
 	instanceToAsgMutex  sync.Mutex
 	service             autoScalingWrapper
@@ -41,10 +42,11 @@ type autoScalingGroups struct {
 
 func newAutoScalingGroups(service autoScalingWrapper) (*autoScalingGroups, error) {
 	registry := &autoScalingGroups{
-		registeredAsgs: make([]*asgInformation, 0),
-		service:        service,
-		instanceToAsg:  make(map[AwsRef]*Asg),
-		interrupt:      make(chan struct{}),
+		registeredAsgs:     make([]*asgInformation, 0),
+		service:            service,
+		instanceToAsg:      make(map[AwsRef]*Asg),
+		notInRegisteredAsg: make(map[AwsRef]bool),
+		interrupt:          make(chan struct{}),
 	}
 	go wait.Until(func() {
 		if err := registry.regenerateCache(); err != nil {
@@ -67,6 +69,7 @@ func (m *autoScalingGroups) Register(asg *Asg) bool {
 			}
 			m.registeredAsgs[i].config = asg
 			glog.V(4).Infof("Updated ASG %s", asg.AwsRef.Name)
+			m.invalidateUnownedInstanceCache()
 			return true
 		}
 	}
@@ -75,6 +78,7 @@ func (m *autoScalingGroups) Register(asg *Asg) bool {
 	m.registeredAsgs = append(m.registeredAsgs, &asgInformation{
 		config: asg,
 	})
+	m.invalidateUnownedInstanceCache()
 	return true
 }
 
@@ -110,6 +114,12 @@ func (m *autoScalingGroups) FindForInstance(instance *AwsRef) (*Asg, error) {
 	m.instanceToAsgMutex.Lock()
 	defer m.instanceToAsgMutex.Unlock()
 
+	if m.notInRegisteredAsg[*instance] {
+		// We already know we don't own this instance. Return early and avoid
+		// additional calls to describe ASGs.
+		return nil, nil
+	}
+
 	if config, found := m.instanceToAsg[*instance]; found {
 		return config, nil
 	}
@@ -119,9 +129,18 @@ func (m *autoScalingGroups) FindForInstance(instance *AwsRef) (*Asg, error) {
 	if config, found := m.instanceToAsg[*instance]; found {
 		return config, nil
 	}
+
+	m.notInRegisteredAsg[*instance] = true
 	return nil, nil
 }
 
+func (m *autoScalingGroups) invalidateUnownedInstanceCache() {
+	glog.V(4).Info("Invalidating unowned instance cache")
+	m.instanceToAsgMutex.Lock()
+	m.notInRegisteredAsg = make(map[AwsRef]bool)
+	m.instanceToAsgMutex.Unlock()
+}
+
 func (m *autoScalingGroups) regenerateCache() error {
 	m.instanceToAsgMutex.Lock()
 	defer m.instanceToAsgMutex.Unlock()