5.4. 基于 Go 的 Operator

• 已安装 operator SDK CLI
• 已安装 OpenShift CLI（oc）v4.8+
• 使用具有 cluster-admin 权限的 oc 登录到 OpenShift Container Platform 4.8 集群
• 要允许集群拉取镜像，推送镜像的存储库必须设置为公共的存储库，或必须配置一个镜像 pull secret

• 如需更深入地了解如何构建基于 Go 的 Operator，请参阅基于 Go 的 Operator SDK 指南。

• 已安装 operator SDK CLI
• 已安装 OpenShift CLI（oc）v4.8+
• 使用具有 cluster-admin 权限的 oc 登录到 OpenShift Container Platform 4.8 集群
• 要允许集群拉取镜像，推送镜像的存储库必须设置为公共的存储库，或必须配置一个镜像 pull secret

流程

• 在本例中，将生成的控制器文件 controllers/memcached_controller.go 替换为以下示例实现：

  例 5.28. memcached_controller.go示例

  /*
  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"
  
  	cachev1alpha1 "github.com/example/memcached-operator/api/v1alpha1"
  )
  
  // 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)
  
  	// Fetch the Memcached instance
  	memcached := &cachev1alpha1.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 *cachev1alpha1.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(&cachev1alpha1.Memcached{}).
  		Owns(&appsv1.Deployment{}).
  		Complete(r)
  }

  示例控制器为每个 Memcached 自定义资源（CR）运行以下协调逻辑：

  • 如果尚无 Memcached 部署，创建一个。
  • 确保部署大小与 Memcached CR spec 指定的大小相同。
  • 使用 memcached Pod 的名称更新 Memcached CR 状态。

• 作为 Go 程序在集群外本地运行。
• 作为集群的部署运行。
• 捆绑 Operator，并使用 Operator Lifecycle Manager（OLM）在集群中部署。

先决条件

• 在集群中安装的 Memcached Operator 示例，它提供 Memcached CR