Implement autoscaling from zero by auto-populating AWSMachineTemplate capacity

Author: LiangquanLi930

config/rbac/role.yaml

@@ -175,6 +175,7 @@ rules:
   resources:
   - awsclusters/status
   - awsfargateprofiles/status
+  - awsmachinetemplates/status
   - rosaclusters/status
   - rosanetworks/status
   - rosaroleconfigs/status

controllers/awsmachinetemplate_controller.go

@@ -0,0 +1,193 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package controllers
+
+import (
+	"context"
+
+	"github.com/aws/aws-sdk-go-v2/service/ec2"
+	ec2types "github.com/aws/aws-sdk-go-v2/service/ec2/types"
+	"github.com/pkg/errors"
+	corev1 "k8s.io/api/core/v1"
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
+	"k8s.io/apimachinery/pkg/api/resource"
+	ctrl "sigs.k8s.io/controller-runtime"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/controller"
+
+	infrav1 "sigs.k8s.io/cluster-api-provider-aws/v2/api/v1beta2"
+	"sigs.k8s.io/cluster-api-provider-aws/v2/pkg/cloud/scope"
+	"sigs.k8s.io/cluster-api-provider-aws/v2/pkg/logger"
+	"sigs.k8s.io/cluster-api-provider-aws/v2/pkg/record"
+	"sigs.k8s.io/cluster-api/util"
+	"sigs.k8s.io/cluster-api/util/predicates"
+)
+
+// AWSMachineTemplateReconciler reconciles AWSMachineTemplate objects.
+//
+// This controller automatically populates capacity information for AWSMachineTemplate resources
+// to enable autoscaling from zero.
+//
+// See: https://github.com/kubernetes-sigs/cluster-api/blob/main/docs/proposals/20210310-opt-in-autoscaling-from-zero.md
+type AWSMachineTemplateReconciler struct {
+	client.Client
+	WatchFilterValue string
+}
+
+// +kubebuilder:rbac:groups=infrastructure.cluster.x-k8s.io,resources=awsmachinetemplates,verbs=get;list;watch
+// +kubebuilder:rbac:groups=infrastructure.cluster.x-k8s.io,resources=awsmachinetemplates/status,verbs=get;update;patch
+// +kubebuilder:rbac:groups=infrastructure.cluster.x-k8s.io,resources=awsclusters,verbs=get;list;watch
+// +kubebuilder:rbac:groups=cluster.x-k8s.io,resources=clusters,verbs=get;list;watch
+// +kubebuilder:rbac:groups="",resources=events,verbs=get;list;watch;create;update;patch
+
+// Reconcile populates capacity information for AWSMachineTemplate.
+func (r *AWSMachineTemplateReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
+	log := logger.FromContext(ctx)
+
+	// Fetch the AWSMachineTemplate
+	awsMachineTemplate := &infrav1.AWSMachineTemplate{}
+	if err := r.Get(ctx, req.NamespacedName, awsMachineTemplate); err != nil {
+		if apierrors.IsNotFound(err) {
+			return ctrl.Result{}, nil
+		}
+		return ctrl.Result{}, err
+	}
+
+	// Skip if capacity is already set
+	if len(awsMachineTemplate.Status.Capacity) > 0 {
+		return ctrl.Result{}, nil
+	}
+
+	// Get instance type from spec
+	instanceType := awsMachineTemplate.Spec.Template.Spec.InstanceType
+	if instanceType == "" {
+		return ctrl.Result{}, nil
+	}
+
+	// Find the region by checking ownerReferences
+	region, err := r.getRegion(ctx, awsMachineTemplate)
+	if err != nil {
+		return ctrl.Result{}, err
+	}
+	if region == "" {
+		return ctrl.Result{}, nil
+	}
+
+	// Create global scope for this region
+	// Reference: exp/instancestate/awsinstancestate_controller.go:68-76
+	globalScope, err := scope.NewGlobalScope(scope.GlobalScopeParams{
+		ControllerName: "awsmachinetemplate",
+		Region:         region,
+	})
+	if err != nil {
+		record.Warnf(awsMachineTemplate, "AWSSessionFailed", "Failed to create AWS session for region %q: %v", region, err)
+		return ctrl.Result{}, nil
+	}
+
+	// Query instance type capacity
+	capacity, err := r.getInstanceTypeCapacity(ctx, globalScope, instanceType)
+	if err != nil {
+		record.Warnf(awsMachineTemplate, "CapacityQueryFailed", "Failed to query capacity for instance type %q: %v", instanceType, err)
+		return ctrl.Result{}, nil
+	}
+
+	// Update status with capacity
+	awsMachineTemplate.Status.Capacity = capacity
+
+	if err := r.Status().Update(ctx, awsMachineTemplate); err != nil {
+		return ctrl.Result{}, errors.Wrap(err, "failed to update AWSMachineTemplate status")
+	}
+
+	log.Info("Successfully populated capacity information", "instanceType", instanceType, "region", region, "capacity", capacity)
+	return ctrl.Result{}, nil
+}
+
+// getRegion finds the region by checking the template's owner cluster reference.
+func (r *AWSMachineTemplateReconciler) getRegion(ctx context.Context, template *infrav1.AWSMachineTemplate) (string, error) {
+	// Get the owner cluster
+	cluster, err := util.GetOwnerCluster(ctx, r.Client, template.ObjectMeta)
+	if err != nil {
+		return "", err
+	}
+	if cluster == nil {
+		return "", errors.New("no owner cluster found")
+	}
+
+	// Get region from AWSCluster (standard EC2-based cluster)
+	if cluster.Spec.InfrastructureRef != nil && cluster.Spec.InfrastructureRef.Kind == "AWSCluster" {
+		awsCluster := &infrav1.AWSCluster{}
+		if err := r.Get(ctx, client.ObjectKey{
+			Namespace: cluster.Namespace,
+			Name:      cluster.Spec.InfrastructureRef.Name,
+		}, awsCluster); err != nil {
+			if !apierrors.IsNotFound(err) {
+				return "", errors.Wrapf(err, "failed to get AWSCluster %s/%s", cluster.Namespace, cluster.Spec.InfrastructureRef.Name)
+			}
+		} else if awsCluster.Spec.Region != "" {
+			return awsCluster.Spec.Region, nil
+		}
+	}
+
+	return "", nil
+}
+
+// getInstanceTypeCapacity queries AWS EC2 API for instance type capacity.
+func (r *AWSMachineTemplateReconciler) getInstanceTypeCapacity(ctx context.Context, globalScope *scope.GlobalScope, instanceType string) (corev1.ResourceList, error) {
+	// Create EC2 client from global scope
+	ec2Client := ec2.NewFromConfig(globalScope.Session())
+
+	// Query instance type information
+	input := &ec2.DescribeInstanceTypesInput{
+		InstanceTypes: []ec2types.InstanceType{ec2types.InstanceType(instanceType)},
+	}
+
+	result, err := ec2Client.DescribeInstanceTypes(ctx, input)
+	if err != nil {
+		return nil, errors.Wrapf(err, "failed to describe instance type %q", instanceType)
+	}
+
+	if len(result.InstanceTypes) == 0 {
+		return nil, errors.Errorf("no information found for instance type %q", instanceType)
+	}
+
+	// Extract capacity information
+	info := result.InstanceTypes[0]
+	resourceList := corev1.ResourceList{}
+
+	// CPU
+	if info.VCpuInfo != nil && info.VCpuInfo.DefaultVCpus != nil {
+		resourceList[corev1.ResourceCPU] = *resource.NewQuantity(int64(*info.VCpuInfo.DefaultVCpus), resource.DecimalSI)
+	}
+
+	// Memory
+	if info.MemoryInfo != nil && info.MemoryInfo.SizeInMiB != nil {
+		memoryBytes := *info.MemoryInfo.SizeInMiB * 1024 * 1024
+		resourceList[corev1.ResourceMemory] = *resource.NewQuantity(memoryBytes, resource.BinarySI)
+	}
+	return resourceList, nil
+}
+
+// SetupWithManager sets up the controller with the Manager.
+func (r *AWSMachineTemplateReconciler) SetupWithManager(ctx context.Context, mgr ctrl.Manager, options controller.Options) error {
+	log := logger.FromContext(ctx)
+
+	return ctrl.NewControllerManagedBy(mgr).
+		For(&infrav1.AWSMachineTemplate{}).
+		WithOptions(options).
+		WithEventFilter(predicates.ResourceHasFilterLabel(mgr.GetScheme(), log.GetLogger(), r.WatchFilterValue)).
+		Complete(r)
+}