✨ Cache architecture for each instance type in memory to avoid unnecessary AWS API requests

controllers/awsmachine_controller_test.go

@@ -147,7 +147,7 @@ func TestAWSMachineReconcilerIntegrationTests(t *testing.T) {
 		ms.AWSMachine.Status.InstanceState = &infrav1.InstanceStateRunning
 		ms.Machine.Labels = map[string]string{clusterv1.MachineControlPlaneLabel: ""}
 
-		ec2Svc := ec2Service.NewService(cs)
+		ec2Svc := ec2Service.NewService(cs).WithInstanceTypeArchitectureCache(nil)
 		ec2Svc.EC2Client = ec2Mock
 		reconciler.ec2ServiceFactory = func(scope scope.EC2Scope) services.EC2Interface {
 			return ec2Svc

pkg/cloud/services/ec2/ami.go

@@ -38,6 +38,7 @@ import (
 	"sigs.k8s.io/cluster-api-provider-aws/v2/pkg/cloud/endpoints"
 	"sigs.k8s.io/cluster-api-provider-aws/v2/pkg/cloud/services/common"
 	"sigs.k8s.io/cluster-api-provider-aws/v2/pkg/record"
+	"sigs.k8s.io/cluster-api-provider-aws/v2/util/cache"
 )
 
 const (
@@ -124,6 +125,15 @@ func GenerateAmiName(amiNameFormat, baseOS, kubernetesVersion string) (string, e
 
 // Determine architecture based on instance type.
 func (s *Service) pickArchitectureForInstanceType(instanceType ec2types.InstanceType) (string, error) {
+	logger := s.scope.GetLogger().WithValues("instance type", instanceType)
+
+	if s.InstanceTypeArchitectureCache != nil {
+		if entry, ok := s.InstanceTypeArchitectureCache.Has(string(instanceType)); ok {
+			logger.Info("Chosen architecture from cache", "architecture", entry.Architecture)
+			return entry.Architecture, nil
+		}
+	}
+
 	descInstanceTypeInput := &ec2.DescribeInstanceTypesInput{
 		InstanceTypes: []ec2types.InstanceType{instanceType},
 	}
@@ -144,7 +154,7 @@ func (s *Service) pickArchitectureForInstanceType(instanceType ec2types.Instance
 
 	supportedArchs := describeInstanceTypeResult.InstanceTypes[0].ProcessorInfo.SupportedArchitectures
 
-	logger := s.scope.GetLogger().WithValues("instance type", instanceType, "supported architectures", supportedArchs)
+	logger = logger.WithValues("supportedArchs", supportedArchs)
 	logger.Info("Obtained a list of supported architectures for instance type")
 
 	// Loop over every supported architecture for the instance type
@@ -165,6 +175,13 @@ archCheck:
 		return "", fmt.Errorf("unable to find preferred architecture for instance type %q", instanceType)
 	}
 
+	if s.InstanceTypeArchitectureCache != nil {
+		s.InstanceTypeArchitectureCache.Add(cache.InstanceTypeArchitectureCacheEntry{
+			InstanceType: instanceType,
+			Architecture: architecture,
+		})
+	}
+
 	logger.Info("Chosen architecture", "architecture", architecture)
 
 	return architecture, nil

pkg/cloud/services/ec2/instances_test.go

@@ -5971,7 +5971,7 @@ func TestCreateInstance(t *testing.T) {
 			machineScope.AWSMachine.Spec = *tc.machineConfig
 			tc.expect(ec2Mock.EXPECT())
 
-			s := NewService(clusterScope)
+			s := NewService(clusterScope).WithInstanceTypeArchitectureCache(nil)
 			s.EC2Client = ec2Mock
 
 			instance, err := s.CreateInstance(context.TODO(), machineScope, data, "")

pkg/cloud/services/ec2/launchtemplate_test.go

@@ -2028,7 +2028,7 @@ func TestDiscoverLaunchTemplateAMI(t *testing.T) {
 				tc.expect(ec2Mock.EXPECT())
 			}
 
-			s := NewService(cs)
+			s := NewService(cs).WithInstanceTypeArchitectureCache(nil)
 			s.EC2Client = ec2Mock
 
 			id, err := s.DiscoverLaunchTemplateAMI(context.TODO(), ms)
@@ -2104,7 +2104,7 @@ func TestDiscoverLaunchTemplateAMIForEKS(t *testing.T) {
 				tc.expectSSM(ssmMock.EXPECT())
 			}
 
-			s := NewService(mcps)
+			s := NewService(mcps).WithInstanceTypeArchitectureCache(nil)
 			s.EC2Client = ec2Mock
 			s.SSMClient = ssmMock
 

pkg/cloud/services/ec2/service.go

@@ -22,6 +22,7 @@ import (
 	"sigs.k8s.io/cluster-api-provider-aws/v2/pkg/cloud/services/common"
 	"sigs.k8s.io/cluster-api-provider-aws/v2/pkg/cloud/services/network"
 	"sigs.k8s.io/cluster-api-provider-aws/v2/pkg/cloud/services/ssm"
+	"sigs.k8s.io/cluster-api-provider-aws/v2/util/cache"
 )
 
 // Service holds a collection of interfaces.
@@ -38,14 +39,23 @@ type Service struct {
 	// RetryEC2Client is used for dedicated host operations with enhanced retry configuration
 	// If nil, a new retry client will be created as needed
 	RetryEC2Client common.EC2API
+
+	InstanceTypeArchitectureCache cache.InstanceTypeArchitectureCache
 }
 
 // NewService returns a new service given the ec2 api client.
 func NewService(clusterScope scope.EC2Scope) *Service {
 	return &Service{
-		scope:      clusterScope,
-		EC2Client:  scope.NewEC2Client(clusterScope, clusterScope, clusterScope, clusterScope.InfraCluster()),
-		SSMClient:  scope.NewSSMClient(clusterScope, clusterScope, clusterScope, clusterScope.InfraCluster()),
-		netService: network.NewService(clusterScope.(scope.NetworkScope)),
+		scope:                         clusterScope,
+		EC2Client:                     scope.NewEC2Client(clusterScope, clusterScope, clusterScope, clusterScope.InfraCluster()),
+		SSMClient:                     scope.NewSSMClient(clusterScope, clusterScope, clusterScope, clusterScope.InfraCluster()),
+		netService:                    network.NewService(clusterScope.(scope.NetworkScope)),
+		InstanceTypeArchitectureCache: cache.InstanceTypeArchitectureCacheSingleton,
 	}
 }
+
+// WithInstanceTypeArchitectureCache overrides the cache for InstanceTypeArchitectureCacheEntry items (nil disables caching).
+func (s *Service) WithInstanceTypeArchitectureCache(instanceTypeArchitectureCache cache.InstanceTypeArchitectureCache) *Service {
+	s.InstanceTypeArchitectureCache = instanceTypeArchitectureCache
+	return s
+}

util/cache/cache.go

@@ -0,0 +1,46 @@
+/*
+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 cache implements caching helper functions.
+package cache
+
+import (
+	"time"
+
+	ec2types "github.com/aws/aws-sdk-go-v2/service/ec2/types"
+
+	capicache "sigs.k8s.io/cluster-api/util/cache"
+)
+
+// InstanceTypeArchitectureCacheEntry caches DescribeInstanceTypes results since they are not expected to change.
+type InstanceTypeArchitectureCacheEntry struct {
+	InstanceType ec2types.InstanceType
+	Architecture string
+}
+
+// Key returns the cache key of a InstanceTypeArchitectureCacheEntry.
+func (e InstanceTypeArchitectureCacheEntry) Key() string {
+	return string(e.InstanceType)
+}
+
+// InstanceTypeArchitectureCache stores InstanceTypeArchitectureCacheEntry items.
+type InstanceTypeArchitectureCache = capicache.Cache[InstanceTypeArchitectureCacheEntry]
+
+var (
+	// InstanceTypeArchitectureCacheSingleton is the singleton cache for InstanceTypeArchitectureCacheEntry items.
+	// It should be used in all relevant controllers (and possibly disabled for unit tests).
+	InstanceTypeArchitectureCacheSingleton InstanceTypeArchitectureCache = capicache.New[InstanceTypeArchitectureCacheEntry](2 * time.Hour)
+)