refactor: assemble and reuse Instance dependencies

internal/controller/postgresqlinstance_state_machine.go

@@ -28,12 +28,12 @@ import (
 type instancePhaseHandler func(context.Context, *databasev1alpha1.PostgreSQLInstance) (ctrl.Result, error)
 
 type instanceStateMachine struct {
-	initializer PostgreSQLInstanceInitializer
-	handlers    map[databasev1alpha1.PostgreSQLInstancePhase]instancePhaseHandler
+	instances PostgreSQLInstances
+	handlers  map[databasev1alpha1.PostgreSQLInstancePhase]instancePhaseHandler
 }
 
-func newInstanceStateMachine(initializer PostgreSQLInstanceInitializer) *instanceStateMachine {
-	m := &instanceStateMachine{initializer: initializer}
+func newInstanceStateMachine(instances PostgreSQLInstances) *instanceStateMachine {
+	m := &instanceStateMachine{instances: instances}
 	m.handlers = map[databasev1alpha1.PostgreSQLInstancePhase]instancePhaseHandler{
 		databasev1alpha1.PostgreSQLInstancePhasePending:              m.pending,
 		databasev1alpha1.PostgreSQLInstancePhaseValidating:           m.validate,
@@ -45,6 +45,8 @@ func newInstanceStateMachine(initializer PostgreSQLInstanceInitializer) *instanc
 }
 
 func (m *instanceStateMachine) reconcile(ctx context.Context, instance *databasev1alpha1.PostgreSQLInstance) (ctrl.Result, error) {
+	// Dispatch exactly one handler from the persisted checkpoint. A handler performs
+	// its state action and returns the next checkpoint for the Reconciler to save.
 	phase := instance.Status.Phase
 	if !instance.DeletionTimestamp.IsZero() {
 		phase = databasev1alpha1.PostgreSQLInstancePhaseDeleting
@@ -69,15 +71,13 @@ func (m *instanceStateMachine) reconcile(ctx context.Context, instance *database
 }
 
 func (m *instanceStateMachine) pending(_ context.Context, instance *databasev1alpha1.PostgreSQLInstance) (ctrl.Result, error) {
+	// Persist intent before the next reconcile opens external connections.
 	return advanceInstance(instance, databasev1alpha1.PostgreSQLInstancePhaseValidating,
 		"instance dependencies are being validated"), nil
 }
 
 func (m *instanceStateMachine) validate(ctx context.Context, instance *databasev1alpha1.PostgreSQLInstance) (ctrl.Result, error) {
-	if m.initializer == nil {
-		return ctrl.Result{}, nil
-	}
-	version, err := m.initializer.Validate(ctx, instance)
+	version, err := m.instances.Validate(ctx, instance)
 	if err != nil {
 		return ctrl.Result{}, err
 	}
@@ -87,10 +87,7 @@ func (m *instanceStateMachine) validate(ctx context.Context, instance *databasev
 }
 
 func (m *instanceStateMachine) initializeRegistry(ctx context.Context, instance *databasev1alpha1.PostgreSQLInstance) (ctrl.Result, error) {
-	if m.initializer == nil {
-		return ctrl.Result{}, nil
-	}
-	version, err := m.initializer.InitializeRegistry(ctx, instance)
+	version, err := m.instances.InitializeRegistry(ctx, instance)
 	if err != nil {
 		return ctrl.Result{}, err
 	}
@@ -105,10 +102,7 @@ func (m *instanceStateMachine) ready(ctx context.Context, instance *databasev1al
 	if instance.Status.ObservedGeneration != instance.Generation {
 		return m.pending(ctx, instance)
 	}
-	if m.initializer == nil {
-		return ctrl.Result{}, nil
-	}
-	version, err := m.initializer.Validate(ctx, instance)
+	version, err := m.instances.Validate(ctx, instance)
 	if err != nil {
 		instance.Status.Phase = databasev1alpha1.PostgreSQLInstancePhaseValidating
 		return ctrl.Result{}, err
@@ -118,6 +112,7 @@ func (m *instanceStateMachine) ready(ctx context.Context, instance *databasev1al
 }
 
 func (m *instanceStateMachine) deleting(_ context.Context, instance *databasev1alpha1.PostgreSQLInstance) (ctrl.Result, error) {
+	m.instances.Forget(instance.Name)
 	instance.Status.Phase = databasev1alpha1.PostgreSQLInstancePhaseDeleting
 	setReconcilingCondition(&instance.Status.Conditions, instance.Generation, "instance deletion is reconciling")
 	return ctrl.Result{}, nil