5.3.2.4. コントローラーの実装

手順

• この例では、生成されたコントローラーファイル controllers/memcached_controller.go を以下の実装例に置き換えます。

  例5.1 memcached_controller.go の例

  /*
  Copyright 2020.
  
  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 controllers
  
  import (
          appsv1 "k8s.io/api/apps/v1"
          corev1 "k8s.io/api/core/v1"
          "k8s.io/apimachinery/pkg/api/errors"
          metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
          "k8s.io/apimachinery/pkg/types"
          "reflect"
  
          "context"
  
          "github.com/go-logr/logr"
          "k8s.io/apimachinery/pkg/runtime"
          ctrl "sigs.k8s.io/controller-runtime"
          "sigs.k8s.io/controller-runtime/pkg/client"
          ctrllog "sigs.k8s.io/controller-runtime/pkg/log"
  
          cachev1 "github.com/example-inc/memcached-operator/api/v1"
  )
  
  // MemcachedReconciler reconciles a Memcached object
  type MemcachedReconciler struct {
          client.Client
          Log    logr.Logger
          Scheme *runtime.Scheme
  }
  
  // +kubebuilder:rbac:groups=cache.example.com,resources=memcacheds,verbs=get;list;watch;create;update;patch;delete
  // +kubebuilder:rbac:groups=cache.example.com,resources=memcacheds/status,verbs=get;update;patch
  // +kubebuilder:rbac:groups=cache.example.com,resources=memcacheds/finalizers,verbs=update
  // +kubebuilder:rbac:groups=apps,resources=deployments,verbs=get;list;watch;create;update;patch;delete
  // +kubebuilder:rbac:groups=core,resources=pods,verbs=get;list;
  
  // Reconcile is part of the main kubernetes reconciliation loop which aims to
  // move the current state of the cluster closer to the desired state.
  // TODO(user): Modify the Reconcile function to compare the state specified by
  // the Memcached object against the actual cluster state, and then
  // perform operations to make the cluster state reflect the state specified by
  // the user.
  //
  // For more details, check Reconcile and its Result here:
  // - https://pkg.go.dev/sigs.k8s.io/controller-runtime@v0.7.0/pkg/reconcile
  func (r *MemcachedReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
          //log := r.Log.WithValues("memcached", req.NamespacedName)
          log := ctrllog.FromContext(ctx)
          // Fetch the Memcached instance
          memcached := &cachev1.Memcached{}
          err := r.Get(ctx, req.NamespacedName, memcached)
          if err != nil {
                  if errors.IsNotFound(err) {
                          // Request object not found, could have been deleted after reconcile request.
                          // Owned objects are automatically garbage collected. For additional cleanup logic use finalizers.
                          // Return and don't requeue
                          log.Info("Memcached resource not found. Ignoring since object must be deleted")
                          return ctrl.Result{}, nil
                  }
                  // Error reading the object - requeue the request.
                  log.Error(err, "Failed to get Memcached")
                  return ctrl.Result{}, err
          }
  
          // Check if the deployment already exists, if not create a new one
          found := &appsv1.Deployment{}
          err = r.Get(ctx, types.NamespacedName{Name: memcached.Name, Namespace: memcached.Namespace}, found)
          if err != nil && errors.IsNotFound(err) {
                  // Define a new deployment
                  dep := r.deploymentForMemcached(memcached)
                  log.Info("Creating a new Deployment", "Deployment.Namespace", dep.Namespace, "Deployment.Name", dep.Name)
                  err = r.Create(ctx, dep)
                  if err != nil {
                          log.Error(err, "Failed to create new Deployment", "Deployment.Namespace", dep.Namespace, "Deployment.Name", dep.Name)
                          return ctrl.Result{}, err
                  }
                  // Deployment created successfully - return and requeue
                  return ctrl.Result{Requeue: true}, nil
          } else if err != nil {
                  log.Error(err, "Failed to get Deployment")
                  return ctrl.Result{}, err
          }
  
          // Ensure the deployment size is the same as the spec
          size := memcached.Spec.Size
          if *found.Spec.Replicas != size {
                  found.Spec.Replicas = &size
                  err = r.Update(ctx, found)
                  if err != nil {
                          log.Error(err, "Failed to update Deployment", "Deployment.Namespace", found.Namespace, "Deployment.Name", found.Name)
                          return ctrl.Result{}, err
                  }
                  // Spec updated - return and requeue
                  return ctrl.Result{Requeue: true}, nil
          }
  
          // Update the Memcached status with the pod names
          // List the pods for this memcached's deployment
          podList := &corev1.PodList{}
          listOpts := []client.ListOption{
                  client.InNamespace(memcached.Namespace),
                  client.MatchingLabels(labelsForMemcached(memcached.Name)),
          }
          if err = r.List(ctx, podList, listOpts...); err != nil {
                  log.Error(err, "Failed to list pods", "Memcached.Namespace", memcached.Namespace, "Memcached.Name", memcached.Name)
                  return ctrl.Result{}, err
          }
          podNames := getPodNames(podList.Items)
  
          // Update status.Nodes if needed
          if !reflect.DeepEqual(podNames, memcached.Status.Nodes) {
                  memcached.Status.Nodes = podNames
                  err := r.Status().Update(ctx, memcached)
                  if err != nil {
                          log.Error(err, "Failed to update Memcached status")
                          return ctrl.Result{}, err
                  }
          }
  
          return ctrl.Result{}, nil
  }
  
  // deploymentForMemcached returns a memcached Deployment object
  func (r *MemcachedReconciler) deploymentForMemcached(m *cachev1.Memcached) *appsv1.Deployment {
          ls := labelsForMemcached(m.Name)
          replicas := m.Spec.Size
  
          dep := &appsv1.Deployment{
                  ObjectMeta: metav1.ObjectMeta{
                          Name:      m.Name,
                          Namespace: m.Namespace,
                  },
                  Spec: appsv1.DeploymentSpec{
                          Replicas: &replicas,
                          Selector: &metav1.LabelSelector{
                                  MatchLabels: ls,
                          },
                          Template: corev1.PodTemplateSpec{
                                  ObjectMeta: metav1.ObjectMeta{
                                          Labels: ls,
                                  },
                                  Spec: corev1.PodSpec{
                                          Containers: []corev1.Container{{
                                                  Image:   "memcached:1.4.36-alpine",
                                                  Name:    "memcached",
                                                  Command: []string{"memcached", "-m=64", "-o", "modern", "-v"},
                                                  Ports: []corev1.ContainerPort{{
                                                          ContainerPort: 11211,
                                                          Name:          "memcached",
                                                  }},
                                          }},
                                  },
                          },
                  },
          }
          // Set Memcached instance as the owner and controller
          ctrl.SetControllerReference(m, dep, r.Scheme)
          return dep
  }
  
  // labelsForMemcached returns the labels for selecting the resources
  // belonging to the given memcached CR name.
  func labelsForMemcached(name string) map[string]string {
          return map[string]string{"app": "memcached", "memcached_cr": name}
  }
  
  // getPodNames returns the pod names of the array of pods passed in
  func getPodNames(pods []corev1.Pod) []string {
          var podNames []string
          for _, pod := range pods {
                  podNames = append(podNames, pod.Name)
          }
          return podNames
  }
  
  // SetupWithManager sets up the controller with the Manager.
  func (r *MemcachedReconciler) SetupWithManager(mgr ctrl.Manager) error {
          return ctrl.NewControllerManagedBy(mgr).
                  For(&cachev1.Memcached{}).
                  Owns(&appsv1.Deployment{}).
                  Complete(r)
  }

  コントローラーのサンプルは、それぞれの Memcached カスタムリソース (CR) について以下の調整 (reconciliation) ロジックを実行します。

  • Memcached デプロイメントを作成します (ない場合)。
  • デプロイメントのサイズが、Memcached CR 仕様で指定されたものと同じであることを確認します。
  • Memcached CR ステータスを memcached Pod の名前に置き換えます。