[Feature] ScaleDown candidate (#1120)

CHANGELOG.md

@@ -8,6 +8,7 @@
 - (Debug Package) Initial commit
 - (Feature) Detach PVC from deployment in Ordered indexing method
 - (Feature) OPS Alerts
+- (Feature) ScaleDown Candidate
 
 ## [1.2.16](https://github.com/arangodb/kube-arangodb/tree/1.2.16) (2022-09-14)
 - (Feature) Add ArangoDeployment ServerGroupStatus

pkg/apis/deployment/annotations.go

@@ -21,10 +21,11 @@
 package deployment
 
 const (
-	ArangoDeploymentAnnotationPrefix         = "deployment.arangodb.com"
-	ArangoDeploymentPodMaintenanceAnnotation = ArangoDeploymentAnnotationPrefix + "/maintenance"
-	ArangoDeploymentPodRotateAnnotation      = ArangoDeploymentAnnotationPrefix + "/rotate"
-	ArangoDeploymentPodReplaceAnnotation     = ArangoDeploymentAnnotationPrefix + "/replace"
-	ArangoDeploymentPodDeleteNow             = ArangoDeploymentAnnotationPrefix + "/delete_now"
-	ArangoDeploymentPlanCleanAnnotation      = "plan." + ArangoDeploymentAnnotationPrefix + "/clean"
+	ArangoDeploymentAnnotationPrefix                = "deployment.arangodb.com"
+	ArangoDeploymentPodMaintenanceAnnotation        = ArangoDeploymentAnnotationPrefix + "/maintenance"
+	ArangoDeploymentPodRotateAnnotation             = ArangoDeploymentAnnotationPrefix + "/rotate"
+	ArangoDeploymentPodReplaceAnnotation            = ArangoDeploymentAnnotationPrefix + "/replace"
+	ArangoDeploymentPodDeleteNow                    = ArangoDeploymentAnnotationPrefix + "/delete_now"
+	ArangoDeploymentPodScaleDownCandidateAnnotation = ArangoDeploymentAnnotationPrefix + "/scale_down_candidate"
+	ArangoDeploymentPlanCleanAnnotation             = "plan." + ArangoDeploymentAnnotationPrefix + "/clean"
 )

pkg/apis/deployment/v1/conditions.go

@@ -68,6 +68,8 @@ const (
 	ConditionTypeSpecAccepted ConditionType = "SpecAccepted"
 	// ConditionTypeMarkedToRemove indicates that the member is marked to be removed.
 	ConditionTypeMarkedToRemove ConditionType = "MarkedToRemove"
+	// ConditionTypeScaleDownCandidate indicates that the member will be picked in ScaleDown operaion.
+	ConditionTypeScaleDownCandidate ConditionType = "ScaleDownCandidate"
 	// ConditionTypeUpgradeFailed indicates that upgrade failed
 	ConditionTypeUpgradeFailed ConditionType = "UpgradeFailed"
 

pkg/apis/deployment/v1/member_status_list.go

@@ -149,6 +149,11 @@ func (l MemberStatusList) SelectMemberToRemove(selectors ...MemberToRemoveSelect
 				return m, nil
 			}
 		}
+		for _, m := range l {
+			if m.Conditions.IsTrue(ConditionTypeScaleDownCandidate) {
+				return m, nil
+			}
+		}
 		// Try to find a not ready member
 		for _, m := range l {
 			if m.Phase.IsPending() {

pkg/apis/deployment/v2alpha1/conditions.go

@@ -68,6 +68,8 @@ const (
 	ConditionTypeSpecAccepted ConditionType = "SpecAccepted"
 	// ConditionTypeMarkedToRemove indicates that the member is marked to be removed.
 	ConditionTypeMarkedToRemove ConditionType = "MarkedToRemove"
+	// ConditionTypeScaleDownCandidate indicates that the member will be picked in ScaleDown operaion.
+	ConditionTypeScaleDownCandidate ConditionType = "ScaleDownCandidate"
 	// ConditionTypeUpgradeFailed indicates that upgrade failed
 	ConditionTypeUpgradeFailed ConditionType = "UpgradeFailed"
 

pkg/apis/deployment/v2alpha1/member_status_list.go

@@ -149,6 +149,11 @@ func (l MemberStatusList) SelectMemberToRemove(selectors ...MemberToRemoveSelect
 				return m, nil
 			}
 		}
+		for _, m := range l {
+			if m.Conditions.IsTrue(ConditionTypeScaleDownCandidate) {
+				return m, nil
+			}
+		}
 		// Try to find a not ready member
 		for _, m := range l {
 			if m.Phase.IsPending() {

pkg/deployment/reconcile/plan_builder_high.go

@@ -58,6 +58,7 @@ func (r *Reconciler) createHighPlan(ctx context.Context, apiObject k8sutil.APIOb
 		ApplyIfEmpty(r.createTopologyMemberConditionPlan).
 		ApplyIfEmpty(r.createRebalancerCheckPlan).
 		ApplyIfEmpty(r.createMemberFailedRestoreHighPlan).
+		ApplyIfEmpty(r.scaleDownCandidate).
 		ApplyWithBackOff(BackOffCheck, time.Minute, r.emptyPlanBuilder)).
 		ApplyIfEmptyWithBackOff(TimezoneCheck, time.Minute, r.createTimezoneUpdatePlan).
 		Apply(r.createBackupInProgressConditionPlan). // Discover backups always

pkg/deployment/reconcile/plan_builder_scale.go

@@ -23,6 +23,7 @@ package reconcile
 import (
 	"context"
 
+	"github.com/arangodb/kube-arangodb/pkg/apis/deployment"
 	api "github.com/arangodb/kube-arangodb/pkg/apis/deployment/v1"
 	"github.com/arangodb/kube-arangodb/pkg/deployment/actions"
 	"github.com/arangodb/kube-arangodb/pkg/deployment/agency"
@@ -173,3 +174,45 @@ func getCleanedServer(ctx reconciler.ArangoAgencyGet) api.MemberToRemoveSelector
 		return "", nil
 	}
 }
+
+func (r *Reconciler) scaleDownCandidate(ctx context.Context, apiObject k8sutil.APIObject,
+	spec api.DeploymentSpec, status api.DeploymentStatus,
+	context PlanBuilderContext) api.Plan {
+	var plan api.Plan
+
+	for _, m := range status.Members.AsList() {
+		cache, ok := context.ACS().ClusterCache(m.Member.ClusterID)
+		if !ok {
+			continue
+		}
+
+		annotationExists := false
+
+		am, ok := cache.ArangoMember().V1().GetSimple(m.Member.ArangoMemberName(context.GetName(), m.Group))
+		if !ok {
+			continue
+		}
+
+		if _, ok := am.Annotations[deployment.ArangoDeploymentPodScaleDownCandidateAnnotation]; ok {
+			annotationExists = true
+		}
+
+		if pod, ok := cache.Pod().V1().GetSimple(m.Member.Pod.GetName()); ok {
+			if _, ok := pod.Annotations[deployment.ArangoDeploymentPodScaleDownCandidateAnnotation]; ok {
+				annotationExists = true
+			}
+		}
+
+		conditionExists := m.Member.Conditions.IsTrue(api.ConditionTypeScaleDownCandidate)
+
+		if annotationExists != conditionExists {
+			if annotationExists {
+				plan = append(plan, updateMemberConditionActionV2("Marked as ScaleDownCandidate", api.ConditionTypeScaleDownCandidate, m.Group, m.Member.ID, true, "Marked as ScaleDownCandidate", "", ""))
+			} else {
+				plan = append(plan, removeMemberConditionActionV2("Unmarked as ScaleDownCandidate", api.ConditionTypeScaleDownCandidate, m.Group, m.Member.ID))
+			}
+		}
+	}
+
+	return plan
+}