Merge pull request #2525 from dlipovetsky/dlipovetsky/prune-launchtem…

…plateversion

🐛 AWSMachinePool: Prune old Launch Template versions

exp/controllers/awsmachinepool_controller.go

@@ -455,6 +455,11 @@ func (r *AWSMachinePoolReconciler) reconcileLaunchTemplate(machinePoolScope *sco
 	// userdata, OR we've discovered a new AMI ID.
 	if needsUpdate || tagsChanged || *imageID != *launchTemplate.AMI.ID || launchTemplateUserDataHash != bootstrapDataHash {
 		machinePoolScope.Info("creating new version for launch template", "existing", launchTemplate, "incoming", machinePoolScope.AWSMachinePool.Spec.AWSLaunchTemplate)
+		// There is a limit to the number of Launch Template Versions.
+		// We ensure that the number of versions does not grow without bound by following a simple rule: Before we create a new version, we delete one old version, if there is at least one old version that is not in use.
+		if err := ec2svc.PruneLaunchTemplateVersions(machinePoolScope.AWSMachinePool.Status.LaunchTemplateID); err != nil {
+			return err
+		}
 		if err := ec2svc.CreateLaunchTemplateVersion(machinePoolScope, imageID, bootstrapData); err != nil {
 			return err
 		}

pkg/cloud/services/ec2/launchtemplate.go

@@ -20,6 +20,7 @@ import (
 	"encoding/base64"
 	"reflect"
 	"sort"
+	"strconv"
 	"strings"
 
 	"github.com/aws/aws-sdk-go/aws"
@@ -245,6 +246,63 @@ func (s *Service) DeleteLaunchTemplate(id string) error {
 	return nil
 }
 
+// PruneLaunchTemplateVersions deletes one old launch template version.
+// It does not delete the "latest" version, because that version may still be in use.
+// It does not delete the "default" version, because that version cannot be deleted.
+// It does not assume that versions are sequential. Versions may be deleted out of band.
+func (s *Service) PruneLaunchTemplateVersions(id string) error {
+	// When there is one version available, it is the default and the latest.
+	// When there are two versions available, one the is the default, the other is the latest.
+	// Therefore we only prune when there are at least 3 versions available.
+	const minCountToAllowPrune = 3
+
+	input := &ec2.DescribeLaunchTemplateVersionsInput{
+		LaunchTemplateId: aws.String(id),
+		MinVersion:       aws.String("0"),
+		MaxVersion:       aws.String(expinfrav1.LaunchTemplateLatestVersion),
+		MaxResults:       aws.Int64(minCountToAllowPrune),
+	}
+
+	out, err := s.EC2Client.DescribeLaunchTemplateVersions(input)
+	if err != nil {
+		s.scope.Info("", "aerr", err.Error())
+		return err
+	}
+
+	// len(out.LaunchTemplateVersions)	|	items
+	// -------------------------------- + -----------------------
+	// 								1	|	[default/latest]
+	// 								2	|	[default, latest]
+	// 								3	| 	[default, versionToPrune, latest]
+	if len(out.LaunchTemplateVersions) < minCountToAllowPrune {
+		return nil
+	}
+	versionToPrune := out.LaunchTemplateVersions[1].VersionNumber
+	return s.deleteLaunchTemplateVersion(id, versionToPrune)
+}
+
+func (s *Service) deleteLaunchTemplateVersion(id string, version *int64) error {
+	s.scope.V(2).Info("Deleting launch template version", "id", id)
+
+	if version == nil {
+		return errors.New("version is a nil pointer")
+	}
+	versions := []string{strconv.FormatInt(*version, 10)}
+
+	input := &ec2.DeleteLaunchTemplateVersionsInput{
+		LaunchTemplateId: aws.String(id),
+		Versions:         aws.StringSlice(versions),
+	}
+
+	_, err := s.EC2Client.DeleteLaunchTemplateVersions(input)
+	if err != nil {
+		return err
+	}
+
+	s.scope.V(2).Info("Deleted launch template", "id", id, "version", *version)
+	return nil
+}
+
 // SDKToLaunchTemplate converts an AWS EC2 SDK instance to the CAPA instance type.
 func (s *Service) SDKToLaunchTemplate(d *ec2.LaunchTemplateVersion) (*expinfrav1.AWSLaunchTemplate, string, error) {
 	v := d.LaunchTemplateData

pkg/cloud/services/interfaces.go

@@ -64,6 +64,7 @@ type EC2MachineInterface interface {
 	GetLaunchTemplateID(id string) (string, error)
 	CreateLaunchTemplate(scope *scope.MachinePoolScope, imageID *string, userData []byte) (string, error)
 	CreateLaunchTemplateVersion(scope *scope.MachinePoolScope, imageID *string, userData []byte) error
+	PruneLaunchTemplateVersions(id string) error
 	DeleteLaunchTemplate(id string) error
 	LaunchTemplateNeedsUpdate(scope *scope.MachinePoolScope, incoming *expinfrav1.AWSLaunchTemplate, existing *expinfrav1.AWSLaunchTemplate) (bool, error)
 }