[Feature] Allow Volume Shrink and DBServer replacement

pkg/apis/deployment/annotations.go

@@ -26,4 +26,5 @@ const (
 	ArangoDeploymentAnnotationPrefix         = "deployment.arangodb.com"
 	ArangoDeploymentPodMaintenanceAnnotation = ArangoDeploymentAnnotationPrefix + "/maintenance"
 	ArangoDeploymentPodRotateAnnotation      = ArangoDeploymentAnnotationPrefix + "/rotate"
+	ArangoDeploymentPodReplaceAnnotation     = ArangoDeploymentAnnotationPrefix + "/replace"
 )

pkg/apis/deployment/v1/conditions.go

@@ -61,6 +61,8 @@ const (
 	ConditionTypeTerminating ConditionType = "Terminating"
 	// ConditionTypeTerminating indicates that the deployment is up to date.
 	ConditionTypeUpToDate ConditionType = "UpToDate"
+	// ConditionTypeMarkedToRemove indicates that the member is marked to be removed.
+	ConditionTypeMarkedToRemove ConditionType = "MarkedToRemove"
 )
 
 // Condition represents one current condition of a deployment or deployment member.

pkg/apis/deployment/v1/member_status_list.go

@@ -142,6 +142,12 @@ func (l *MemberStatusList) removeByID(id string) error {
 // Returns an error if the list is empty.
 func (l MemberStatusList) SelectMemberToRemove() (MemberStatus, error) {
 	if len(l) > 0 {
+		// Try to find member with phase to be removed
+		for _, m := range l {
+			if m.Conditions.IsTrue(ConditionTypeMarkedToRemove) {
+				return m, nil
+			}
+		}
 		// Try to find a not ready member
 		for _, m := range l {
 			if m.Phase == MemberPhaseNone {

pkg/apis/deployment/v1/plan.go

@@ -41,6 +41,8 @@ const (
 	ActionTypeIdle ActionType = "Idle"
 	// ActionTypeAddMember causes a member to be added.
 	ActionTypeAddMember ActionType = "AddMember"
+	// ActionTypeMarkToRemoveMember marks member to be removed.
+	ActionTypeMarkToRemoveMember ActionType = "MarkToRemoveMember"
 	// ActionTypeRemoveMember causes a member to be removed.
 	ActionTypeRemoveMember ActionType = "RemoveMember"
 	// ActionTypeRecreateMember recreates member. Used when member is still owner of some shards.

pkg/apis/deployment/v1/server_group_spec.go

@@ -83,7 +83,8 @@ type ServerGroupSpec struct {
 	// VolumeClaimTemplate specifies a template for volume claims
 	VolumeClaimTemplate *core.PersistentVolumeClaim `json:"volumeClaimTemplate,omitempty"`
 	// VolumeResizeMode specified resize mode for pvc
-	VolumeResizeMode *PVCResizeMode `json:"pvcResizeMode,omitempty"`
+	VolumeResizeMode  *PVCResizeMode `json:"pvcResizeMode,omitempty"`
+	VolumeAllowShrink *bool          `json:"volumeAllowShrink,omitempty"`
 	// AntiAffinity specified additional antiAffinity settings in ArangoDB Pod definitions
 	AntiAffinity *core.PodAntiAffinity `json:"antiAffinity,omitempty"`
 	// Affinity specified additional affinity settings in ArangoDB Pod definitions
@@ -614,3 +615,11 @@ func (s ServerGroupSpec) ResetImmutableFields(group ServerGroup, fieldPrefix str
 	}
 	return resetFields
 }
+
+func (s ServerGroupSpec) GetVolumeAllowShrink() bool {
+	if s.VolumeAllowShrink == nil {
+		return false // Default value
+	}
+
+	return *s.VolumeAllowShrink
+}

pkg/deployment/reconcile/action_add_member.go

@@ -65,5 +65,20 @@ func (a *actionAddMember) Start(ctx context.Context) (bool, error) {
 		return false, maskAny(err)
 	}
 	a.newMemberID = newID
+
+	if _, ok := a.action.Params[api.ActionTypeWaitForMemberUp.String()]; ok {
+		a.actionCtx.WithStatusUpdate(func(s *api.DeploymentStatus) bool {
+			s.Plan = append(s.Plan, api.NewAction(api.ActionTypeWaitForMemberInSync, a.action.Group, newID, "Wait for member in sync after creation"))
+			return true
+		})
+	}
+
+	if _, ok := a.action.Params[api.ActionTypeWaitForMemberInSync.String()]; ok {
+		a.actionCtx.WithStatusUpdate(func(s *api.DeploymentStatus) bool {
+			s.Plan = append(s.Plan, api.NewAction(api.ActionTypeWaitForMemberInSync, a.action.Group, newID, "Wait for member in sync after creation"))
+			return true
+		})
+	}
+
 	return true, nil
 }

pkg/deployment/reconcile/action_mark_to_remove_member.go

@@ -0,0 +1,78 @@
+//
+// DISCLAIMER
+//
+// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+//
+// 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.
+//
+// Copyright holder is ArangoDB GmbH, Cologne, Germany
+//
+// Author Ewout Prangsma
+//
+
+package reconcile
+
+import (
+	"context"
+
+	api "github.com/arangodb/kube-arangodb/pkg/apis/deployment/v1"
+	"github.com/rs/zerolog"
+)
+
+func init() {
+	registerAction(api.ActionTypeMarkToRemoveMember, newMarkToRemoveMemberAction)
+}
+
+func newMarkToRemoveMemberAction(log zerolog.Logger, action api.Action, actionCtx ActionContext) Action {
+	a := &actionMarkToRemove{}
+
+	a.actionImpl = newActionImplDefRef(log, action, actionCtx, addMemberTimeout)
+
+	return a
+}
+
+type actionMarkToRemove struct {
+	// actionImpl implement timeout and member id functions
+	actionImpl
+
+	// actionEmptyCheckProgress implement check progress with empty implementation
+	actionEmptyCheckProgress
+}
+
+func (a *actionMarkToRemove) Start(ctx context.Context) (bool, error) {
+	if a.action.Group != api.ServerGroupDBServers {
+		return true, nil
+	}
+
+	return true, a.actionCtx.WithStatusUpdate(func(s *api.DeploymentStatus) bool {
+		member, group, ok := s.Members.ElementByID(a.action.MemberID)
+		if !ok {
+			return false
+		}
+
+		if group != a.action.Group {
+			return false
+		}
+
+		if !member.Conditions.Update(api.ConditionTypeMarkedToRemove, true, "Member marked to be removed", "") {
+			return false
+		}
+
+		if err := s.Members.Update(member, group); err != nil {
+			a.log.Warn().Err(err).Str("Member", member.ID).Msgf("Unable to update member")
+			return false
+		}
+
+		return true
+	})
+}

pkg/deployment/reconcile/action_pvc_resize.go

@@ -98,9 +98,18 @@ func (a *actionPVCResize) Start(ctx context.Context) (bool, error) {
 
 				return false, nil
 			} else if cmp > 0 {
-				log.Error().Str("server-group", group.AsRole()).Str("pvc-storage-size", volumeSize.String()).Str("requested-size", requestedSize.String()).
-					Msg("Volume size should not shrink")
-				a.actionCtx.CreateEvent(k8sutil.NewCannotShrinkVolumeEvent(a.actionCtx.GetAPIObject(), pvc.Name))
+				if groupSpec.GetVolumeAllowShrink() && group == api.ServerGroupDBServers {
+					if err := a.actionCtx.WithStatusUpdate(func(s *api.DeploymentStatus) bool {
+						s.Plan = append(s.Plan, api.NewAction(api.ActionTypeMarkToRemoveMember, group, m.ID))
+						return true
+					}); err != nil {
+						log.Error().Err(err).Msg("Unable to mark instance to be replaced")
+					}
+				} else {
+					log.Error().Str("server-group", group.AsRole()).Str("pvc-storage-size", volumeSize.String()).Str("requested-size", requestedSize.String()).
+						Msg("Volume size should not shrink")
+					a.actionCtx.CreateEvent(k8sutil.NewCannotShrinkVolumeEvent(a.actionCtx.GetAPIObject(), pvc.Name))
+				}
 				return false, nil
 			}
 		}

pkg/deployment/reconcile/plan_builder.go

@@ -214,7 +214,12 @@ func createPlan(ctx context.Context, log zerolog.Logger, apiObject k8sutil.APIOb
 
 	// Check for scale up/down
 	if plan.IsEmpty() {
-		plan = pb.Apply(createScaleMemeberPlan)
+		plan = pb.Apply(createScaleMemberPlan)
+	}
+
+	// Check for members to be removed
+	if plan.IsEmpty() {
+		plan = pb.Apply(createReplaceMemberPlan)
 	}
 
 	// Check for the need to rotate one or more members

pkg/deployment/reconcile/plan_builder_rotate_upgrade.go

@@ -144,8 +144,14 @@ func createRotateOrUpgradePlanInternal(log zerolog.Logger, apiObject k8sutil.API
 			}
 
 			if pod.Annotations != nil {
+				if _, ok := pod.Annotations[deployment.ArangoDeploymentPodReplaceAnnotation]; ok && group == api.ServerGroupDBServers {
+					newPlan = api.Plan{api.NewAction(api.ActionTypeMarkToRemoveMember, group, m.ID, "Replace flag present")}
+					continue
+				}
+
 				if _, ok := pod.Annotations[deployment.ArangoDeploymentPodRotateAnnotation]; ok {
 					newPlan = createRotateMemberPlan(log, m, group, "Rotation flag present")
+					continue
 				}
 			}
 		}

pkg/deployment/reconcile/plan_builder_scale.go

@@ -31,7 +31,7 @@ import (
 	"github.com/rs/zerolog"
 )
 
-func createScaleMemeberPlan(ctx context.Context,
+func createScaleMemberPlan(ctx context.Context,
 	log zerolog.Logger, apiObject k8sutil.APIObject,
 	spec api.DeploymentSpec, status api.DeploymentStatus,
 	cachedStatus inspector.Inspector, context PlanBuilderContext) api.Plan {
@@ -102,3 +102,36 @@ func createScalePlan(log zerolog.Logger, members api.MemberStatusList, group api
 	}
 	return plan
 }
+
+func createReplaceMemberPlan(ctx context.Context,
+	log zerolog.Logger, apiObject k8sutil.APIObject,
+	spec api.DeploymentSpec, status api.DeploymentStatus,
+	cachedStatus inspector.Inspector, context PlanBuilderContext) api.Plan {
+
+	var plan api.Plan
+
+	// Replace is only allowed for DBServers
+	switch spec.GetMode() {
+	case api.DeploymentModeCluster:
+		status.Members.ForeachServerInGroups(func(group api.ServerGroup, list api.MemberStatusList) error {
+			for _, member := range list {
+				if !plan.IsEmpty() {
+					return nil
+				}
+				if member.Conditions.IsTrue(api.ConditionTypeMarkedToRemove) {
+					plan = append(plan, api.NewAction(api.ActionTypeAddMember, group, "").
+						AddParam(api.ActionTypeWaitForMemberInSync.String(), "").
+						AddParam(api.ActionTypeWaitForMemberUp.String(), ""))
+					log.Debug().
+						Str("role", group.AsRole()).
+						Msg("Creating replacement plan")
+					return nil
+				}
+			}
+
+			return nil
+		}, api.ServerGroupDBServers)
+	}
+
+	return plan
+}

pkg/deployment/reconcile/plan_builder_storage.go

@@ -115,8 +115,12 @@ func createRotateServerStoragePlan(ctx context.Context,
 							if cmp < 0 {
 								plan = append(plan, pvcResizePlan(log, group, groupSpec, m.ID)...)
 							} else if cmp > 0 {
-								log.Error().Str("server-group", group.AsRole()).Str("pvc-storage-size", volumeSize.String()).Str("requested-size", requestedSize.String()).
-									Msg("Volume size should not shrink")
+								if groupSpec.GetVolumeAllowShrink() && group == api.ServerGroupDBServers {
+									plan = append(plan, api.NewAction(api.ActionTypeMarkToRemoveMember, group, m.ID))
+								} else {
+									log.Error().Str("server-group", group.AsRole()).Str("pvc-storage-size", volumeSize.String()).Str("requested-size", requestedSize.String()).
+										Msg("Volume size should not shrink")
+								}
 							}
 						}
 					}