Add FetchReservations to GCE Autoscaling client

cluster-autoscaler/cloudprovider/gce/autoscaling_gce_client.go

@@ -77,6 +77,7 @@ type AutoscalingGceClient interface {
 	FetchMigsWithName(zone string, filter *regexp.Regexp) ([]string, error)
 	FetchZones(region string) ([]string, error)
 	FetchAvailableCpuPlatforms() (map[string][]string, error)
+	FetchReservations() ([]*gce.Reservation, error)
 
 	// modifying resources
 	ResizeMig(GceRef, int64) error
@@ -508,3 +509,15 @@ func (client *autoscalingGceClientV1) FetchMigsWithName(zone string, name *regex
 	}
 	return links, nil
 }
+
+func (client *autoscalingGceClientV1) FetchReservations() ([]*gce.Reservation, error) {
+	reservations := make([]*gce.Reservation, 0)
+	call := client.gceService.Reservations.AggregatedList(client.projectId)
+	err := call.Pages(context.TODO(), func(ls *gce.ReservationAggregatedList) error {
+		for _, items := range ls.Items {
+			reservations = append(reservations, items.Reservations...)
+		}
+		return nil
+	})
+	return reservations, err
+}

cluster-autoscaler/cloudprovider/gce/mig_info_provider_test.go

@@ -100,6 +100,10 @@ func (client *mockAutoscalingGceClient) FetchAvailableCpuPlatforms() (map[string
 	return nil, nil
 }
 
+func (client *mockAutoscalingGceClient) FetchReservations() ([]*gce.Reservation, error) {
+	return nil, nil
+}
+
 func (client *mockAutoscalingGceClient) ResizeMig(_ GceRef, _ int64) error {
 	return nil
 }