k8s自定义controller三部曲之三：编写controller代码

本文是《k8s自定义controller三部曲》的终篇，前面的章节中，我们创建了CRD，再通过自动生成代码的工具将controller所需的informer、client等依赖全部准备好，到了本章，就该编写controller的代码了，也就是说，现在已经能监听到Student对象的增删改等事件，接下来就是根据这些事件来做不同的事情，满足个性化的业务需求；

三部曲所有文章链接

《k8s自定义controller三部曲之一:创建CRD（Custom Resource Definition）》；
《k8s自定义controller三部曲之二:自动生成代码》；
《k8s自定义controller三部曲之三：编写controller代码》；

源码下载

接下来详细讲述应用的编码过程，如果您不想自己写代码，也可以在GitHub下载完整的应用源码，地址和链接信息如下表所示：

名称	链接	备注
项目主页	https://github.com/zq2599/blog_demos	该项目在GitHub上的主页
git仓库地址(https)	https://github.com/zq2599/blog_demos.git	该项目源码的仓库地址，https协议
git仓库地址(ssh)	git@github.com:zq2599/blog_demos.git	该项目源码的仓库地址，ssh协议

这个git项目中有多个文件夹，本章源码在k8s_customize_controller这个文件夹下，如下图红框所示：

开始实战

回顾一下，上一章通过自动代码生成工具生成代码后，源码目录的内容如下：

[root@golang k8s_customize_controller]# tree
.
└── pkg├── apis│   └── bolingcavalry│       ├── register.go│       └── v1│           ├── doc.go│           ├── register.go│           ├── types.go│           └── zz_generated.deepcopy.go└── client├── clientset│   └── versioned│       ├── clientset.go│       ├── doc.go│       ├── fake│       │   ├── clientset_generated.go│       │   ├── doc.go│       │   └── register.go│       ├── scheme│       │   ├── doc.go│       │   └── register.go│       └── typed│           └── bolingcavalry│               └── v1│                   ├── bolingcavalry_client.go│                   ├── doc.go│                   ├── fake│                   │   ├── doc.go│                   │   ├── fake_bolingcavalry_client.go│                   │   └── fake_student.go│                   ├── generated_expansion.go│                   └── student.go├── informers│   └── externalversions│       ├── bolingcavalry│       │   ├── interface.go│       │   └── v1│       │       ├── interface.go│       │       └── student.go│       ├── factory.go│       ├── generic.go│       └── internalinterfaces│           └── factory_interfaces.go└── listers└── bolingcavalry└── v1├── expansion_generated.go└── student.go21 directories, 27 files

本章要编写的第一个go文件就是controller.go，在k8s_customize_controller目录下创建controller.go，代码内容如下：

package mainimport ("fmt""time""github.com/golang/glog"corev1 "k8s.io/api/core/v1""k8s.io/apimachinery/pkg/api/errors""k8s.io/apimachinery/pkg/util/runtime"utilruntime "k8s.io/apimachinery/pkg/util/runtime""k8s.io/apimachinery/pkg/util/wait""k8s.io/client-go/kubernetes""k8s.io/client-go/kubernetes/scheme"typedcorev1 "k8s.io/client-go/kubernetes/typed/core/v1""k8s.io/client-go/tools/cache""k8s.io/client-go/tools/record""k8s.io/client-go/util/workqueue"bolingcavalryv1 "github.com/zq2599/k8s-controller-custom-resource/pkg/apis/bolingcavalry/v1"clientset "github.com/zq2599/k8s-controller-custom-resource/pkg/client/clientset/versioned"studentscheme "github.com/zq2599/k8s-controller-custom-resource/pkg/client/clientset/versioned/scheme"informers "github.com/zq2599/k8s-controller-custom-resource/pkg/client/informers/externalversions/bolingcavalry/v1"listers "github.com/zq2599/k8s-controller-custom-resource/pkg/client/listers/bolingcavalry/v1"
)const controllerAgentName = "student-controller"const (SuccessSynced = "Synced"MessageResourceSynced = "Student synced successfully"
)// Controller is the controller implementation for Student resources
type Controller struct {// kubeclientset is a standard kubernetes clientsetkubeclientset kubernetes.Interface// studentclientset is a clientset for our own API groupstudentclientset clientset.InterfacestudentsLister listers.StudentListerstudentsSynced cache.InformerSyncedworkqueue workqueue.RateLimitingInterfacerecorder record.EventRecorder
}// NewController returns a new student controller
func NewController(kubeclientset kubernetes.Interface,studentclientset clientset.Interface,studentInformer informers.StudentInformer) *Controller {utilruntime.Must(studentscheme.AddToScheme(scheme.Scheme))glog.V(4).Info("Creating event broadcaster")eventBroadcaster := record.NewBroadcaster()eventBroadcaster.StartLogging(glog.Infof)eventBroadcaster.StartRecordingToSink(&typedcorev1.EventSinkImpl{Interface: kubeclientset.CoreV1().Events("")})recorder := eventBroadcaster.NewRecorder(scheme.Scheme, corev1.EventSource{Component: controllerAgentName})controller := &Controller{kubeclientset:    kubeclientset,studentclientset: studentclientset,studentsLister:   studentInformer.Lister(),studentsSynced:   studentInformer.Informer().HasSynced,workqueue:        workqueue.NewNamedRateLimitingQueue(workqueue.DefaultControllerRateLimiter(), "Students"),recorder:         recorder,}glog.Info("Setting up event handlers")// Set up an event handler for when Student resources changestudentInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{AddFunc: controller.enqueueStudent,UpdateFunc: func(old, new interface{}) {oldStudent := old.(*bolingcavalryv1.Student)newStudent := new.(*bolingcavalryv1.Student)if oldStudent.ResourceVersion == newStudent.ResourceVersion {//版本一致，就表示没有实际更新的操作，立即返回return}controller.enqueueStudent(new)},DeleteFunc: controller.enqueueStudentForDelete,})return controller
}//在此处开始controller的业务
func (c *Controller) Run(threadiness int, stopCh <-chan struct{}) error {defer runtime.HandleCrash()defer c.workqueue.ShutDown()glog.Info("开始controller业务，开始一次缓存数据同步")if ok := cache.WaitForCacheSync(stopCh, c.studentsSynced); !ok {return fmt.Errorf("failed to wait for caches to sync")}glog.Info("worker启动")for i := 0; i < threadiness; i++ {go wait.Until(c.runWorker, time.Second, stopCh)}glog.Info("worker已经启动")<-stopChglog.Info("worker已经结束")return nil
}func (c *Controller) runWorker() {for c.processNextWorkItem() {}
}// 取数据处理
func (c *Controller) processNextWorkItem() bool {obj, shutdown := c.workqueue.Get()if shutdown {return false}// We wrap this block in a func so we can defer c.workqueue.Done.err := func(obj interface{}) error {defer c.workqueue.Done(obj)var key stringvar ok boolif key, ok = obj.(string); !ok {c.workqueue.Forget(obj)runtime.HandleError(fmt.Errorf("expected string in workqueue but got %#v", obj))return nil}// 在syncHandler中处理业务if err := c.syncHandler(key); err != nil {return fmt.Errorf("error syncing '%s': %s", key, err.Error())}c.workqueue.Forget(obj)glog.Infof("Successfully synced '%s'", key)return nil}(obj)if err != nil {runtime.HandleError(err)return true}return true
}// 处理
func (c *Controller) syncHandler(key string) error {// Convert the namespace/name string into a distinct namespace and namenamespace, name, err := cache.SplitMetaNamespaceKey(key)if err != nil {runtime.HandleError(fmt.Errorf("invalid resource key: %s", key))return nil}// 从缓存中取对象student, err := c.studentsLister.Students(namespace).Get(name)if err != nil {// 如果Student对象被删除了，就会走到这里，所以应该在这里加入执行if errors.IsNotFound(err) {glog.Infof("Student对象被删除，请在这里执行实际的删除业务: %s/%s ...", namespace, name)return nil}runtime.HandleError(fmt.Errorf("failed to list student by: %s/%s", namespace, name))return err}glog.Infof("这里是student对象的期望状态: %#v ...", student)glog.Infof("实际状态是从业务层面得到的，此处应该去的实际状态，与期望状态做对比，并根据差异做出响应(新增或者删除)")c.recorder.Event(student, corev1.EventTypeNormal, SuccessSynced, MessageResourceSynced)return nil
}// 数据先放入缓存，再入队列
func (c *Controller) enqueueStudent(obj interface{}) {var key stringvar err error// 将对象放入缓存if key, err = cache.MetaNamespaceKeyFunc(obj); err != nil {runtime.HandleError(err)return}// 将key放入队列c.workqueue.AddRateLimited(key)
}// 删除操作
func (c *Controller) enqueueStudentForDelete(obj interface{}) {var key stringvar err error// 从缓存中删除指定对象key, err = cache.DeletionHandlingMetaNamespaceKeyFunc(obj)if err != nil {runtime.HandleError(err)return}//再将key放入队列c.workqueue.AddRateLimited(key)
}

上述代码有以下几处关键点：
a. 创建controller的NewController方法中，定义了收到Student对象的增删改消息时的具体处理逻辑，除了同步本地缓存，就是将该对象的key放入消息中；
b. 实际处理消息的方法是syncHandler，这里面可以添加实际的业务代码，来响应Student对象的增删改情况，达到业务目的；

3. 接下来可以写main.go了，不过在此之前把处理系统信号量的辅助类先写好，然后在main.go中会用到（处理例如ctrl+c的退出），在$GOPATH/src/k8s_customize_controller/pkg目录下新建目录signals；
4. 在signals目录下新建文件signal_posix.go：

// +build !windowspackage signalsimport ("os""syscall"
)var shutdownSignals = []os.Signal{os.Interrupt, syscall.SIGTERM}

在signals目录下新建文件signal_posix.go：

package signalsimport ("os"
)var shutdownSignals = []os.Signal{os.Interrupt}

在signals目录下新建文件signal.go：

package signalsimport ("os""os/signal"
)var onlyOneSignalHandler = make(chan struct{})func SetupSignalHandler() (stopCh <-chan struct{}) {close(onlyOneSignalHandler) // panics when called twicestop := make(chan struct{})c := make(chan os.Signal, 2)signal.Notify(c, shutdownSignals...)go func() {<-cclose(stop)<-cos.Exit(1) // second signal. Exit directly.}()return stop
}

接下来可以编写main.go了，在k8s_customize_controller目录下创建main.go文件，内容如下，关键位置已经加了注释，就不再赘述了：

package mainimport ("flag""time""github.com/golang/glog""k8s.io/client-go/kubernetes""k8s.io/client-go/tools/clientcmd"// Uncomment the following line to load the gcp plugin (only required to authenticate against GKE clusters).// _ "k8s.io/client-go/plugin/pkg/client/auth/gcp"clientset "k8s_customize_controller/pkg/client/clientset/versioned"informers "k8s_customize_controller/pkg/client/informers/externalversions""k8s_customize_controller/pkg/signals"
)var (masterURL  stringkubeconfig string
)func main() {flag.Parse()// 处理信号量stopCh := signals.SetupSignalHandler()// 处理入参cfg, err := clientcmd.BuildConfigFromFlags(masterURL, kubeconfig)if err != nil {glog.Fatalf("Error building kubeconfig: %s", err.Error())}kubeClient, err := kubernetes.NewForConfig(cfg)if err != nil {glog.Fatalf("Error building kubernetes clientset: %s", err.Error())}studentClient, err := clientset.NewForConfig(cfg)if err != nil {glog.Fatalf("Error building example clientset: %s", err.Error())}studentInformerFactory := informers.NewSharedInformerFactory(studentClient, time.Second*30)//得到controllercontroller := NewController(kubeClient, studentClient,studentInformerFactory.Bolingcavalry().V1().Students())//启动informergo studentInformerFactory.Start(stopCh)//controller开始处理消息if err = controller.Run(2, stopCh); err != nil {glog.Fatalf("Error running controller: %s", err.Error())}
}func init() {flag.StringVar(&kubeconfig, "kubeconfig", "", "Path to a kubeconfig. Only required if out-of-cluster.")flag.StringVar(&masterURL, "master", "", "The address of the Kubernetes API server. Overrides any value in kubeconfig. Only required if out-of-cluster.")
}

至此，所有代码已经编写完毕，接下来是编译构建；

编译构建和启动

在$GOPATH/src/k8s_customize_controller目录下，执行以下命令：

go get k8s.io/client-go/kubernetes/scheme \
&& go get github.com/golang/glog \
&& go get k8s.io/kube-openapi/pkg/util/proto \
&& go get k8s.io/utils/buffer \
&& go get k8s.io/utils/integer \
&& go get k8s.io/utils/trace

上述脚本将编译过程中依赖的库通过go get方式进行获取，属于笨办法，更好的方法是选用一种包依赖工具，具体的可以参照k8s的官方demo，这个代码中同时提供了godep和vendor两种方式来处理上面的包依赖问题，地址是：https://github.com/kubernetes/sample-controller
解决了包依赖问题后，在$GOPATH/src/k8s_customize_controller目录下执行命令go build，即可在当前目录生成k8s_customize_controller文件；
将文件k8s_customize_controller复制到k8s环境中，记得通过chmod a+x命令给其可执行权限；
执行命令./k8s_customize_controller -kubeconfig=$HOME/.kube/config -alsologtostderr=true，会立即启动controller，看到控制台输出如下：

[root@master 31]# ./k8s_customize_controller -kubeconfig=$HOME/.kube/config -alsologtostderr=true
I0331 23:27:17.909265   21540 controller.go:72] Setting up event handlers
I0331 23:27:17.909450   21540 controller.go:96] 开始controller业务，开始一次缓存数据同步
I0331 23:27:18.110448   21540 controller.go:101] worker启动
I0331 23:27:18.110516   21540 controller.go:106] worker已经启动
I0331 23:27:18.110653   21540 controller.go:181] 这里是student对象的期望状态: &v1.Student{TypeMeta:v1.TypeMeta{Kind:"Student", APIVersion:"bolingcavalry.k8s.io/v1"}, ObjectMeta:v1.ObjectMeta{Name:"object-student", GenerateName:"", Namespace:"default", SelfLink:"/apis/bolingcavalry.k8s.io/v1/namespaces/default/students/object-student", UID:"92927d0d-5360-11e9-9d2a-000c29f1f9c9", ResourceVersion:"310395", Generation:1, CreationTimestamp:v1.Time{Time:time.Time{wall:0x0, ext:63689597785, loc:(*time.Location)(0x1f9c200)}}, DeletionTimestamp:(*v1.Time)(nil), DeletionGracePeriodSeconds:(*int64)(nil), Labels:map[string]string(nil), Annotations:map[string]string{"kubectl.kubernetes.io/last-applied-configuration":"{\"apiVersion\":\"bolingcavalry.k8s.io/v1\",\"kind\":\"Student\",\"metadata\":{\"annotations\":{},\"name\":\"object-student\",\"namespace\":\"default\"},\"spec\":{\"name\":\"张三\",\"school\":\"深圳中学\"}}\n"}, OwnerReferences:[]v1.OwnerReference(nil), Initializers:(*v1.Initializers)(nil), Finalizers:[]string(nil), ClusterName:"", ManagedFields:[]v1.ManagedFieldsEntry(nil)}, Spec:v1.StudentSpec{name:"", school:""}} ...
I0331 23:27:18.111105   21540 controller.go:182] 实际状态是从业务层面得到的，此处应该去的实际状态，与期望状态做对比，并根据差异做出响应(新增或者删除)
I0331 23:27:18.111187   21540 controller.go:145] Successfully synced 'default/object-student'
I0331 23:27:18.112263   21540 event.go:209] Event(v1.ObjectReference{Kind:"Student", Namespace:"default", Name:"object-student", UID:"92927d0d-5360-11e9-9d2a-000c29f1f9c9", APIVersion:"bolingcavalry.k8s.io/v1", ResourceVersion:"310395", FieldPath:""}): type: 'Normal' reason: 'Synced' Student synced successfully

至此，自定义controller已经启动成功了，并且从缓存中获取到了上一章中创建的对象的信息，接下来我们在k8s环境对Student对象做增删改，看看controller是否能做出响应；

验证controller

新开一个窗口连接到k8s环境，新建一个名为new-student.yaml的文件，内容如下：

apiVersion: bolingcavalry.k8s.io/v1
kind: Student
metadata:name: new-student
spec:name: "李四"school: "深圳小学"

在new-student.yaml所在目录执行命令kubectl apply -f new-student.yaml；
返回controller所在的控制台窗口，发现新输出了如下内容，可见新增student对象的事件已经被controller监听并处理：

I0331 23:43:03.789894   21540 controller.go:181] 这里是student对象的期望状态: &v1.Student{TypeMeta:v1.TypeMeta{Kind:"", APIVersion:""}, ObjectMeta:v1.ObjectMeta{Name:"new-student", GenerateName:"", Namespace:"default", SelfLink:"/apis/bolingcavalry.k8s.io/v1/namespaces/default/students/new-student", UID:"abcd77d6-53cb-11e9-9d2a-000c29f1f9c9", ResourceVersion:"370653", Generation:1, CreationTimestamp:v1.Time{Time:time.Time{wall:0x0, ext:63689643783, loc:(*time.Location)(0x1f9c200)}}, DeletionTimestamp:(*v1.Time)(nil), DeletionGracePeriodSeconds:(*int64)(nil), Labels:map[string]string(nil), Annotations:map[string]string{"kubectl.kubernetes.io/last-applied-configuration":"{\"apiVersion\":\"bolingcavalry.k8s.io/v1\",\"kind\":\"Student\",\"metadata\":{\"annotations\":{},\"name\":\"new-student\",\"namespace\":\"default\"},\"spec\":{\"name\":\"李四\",\"school\":\"深圳小学\"}}\n"}, OwnerReferences:[]v1.OwnerReference(nil), Initializers:(*v1.Initializers)(nil), Finalizers:[]string(nil), ClusterName:"", ManagedFields:[]v1.ManagedFieldsEntry(nil)}, Spec:v1.StudentSpec{name:"", school:""}} ...
I0331 23:43:03.790076   21540 controller.go:182] 实际状态是从业务层面得到的，此处应该去的实际状态，与期望状态做对比，并根据差异做出响应(新增或者删除)
I0331 23:43:03.790120   21540 controller.go:145] Successfully synced 'default/new-student'
I0331 23:43:03.790141   21540 event.go:209] Event(v1.ObjectReference{Kind:"Student", Namespace:"default", Name:"new-student", UID:"abcd77d6-53cb-11e9-9d2a-000c29f1f9c9", APIVersion:"bolingcavalry.k8s.io/v1", ResourceVersion:"370653", FieldPath:""}): type: 'Normal' reason: 'Synced' Student synced successfully

接下来您也可以尝试修改和删除已有的Student对象，观察controller控制台的输出，确定是否已经监听到所有student变化的事件，例如删除的事件日志如下：

I0331 23:44:37.236090   21540 controller.go:171] Student对象被删除，请在这里执行实际的删除业务: default/new-student ...
I0331 23:44:37.236118   21540 controller.go:145] Successfully synced 'default/new-student'

小结

至此，controller的编码和验证就全部完成了，现在小结一下自定义controller开发的整个过程：

创建CRD（Custom Resource Definition），令k8s明白我们自定义的API对象；
编写代码，将CRD的情况写入对应的代码中，然后通过自动代码生成工具，将controller之外的informer，client等内容较为固定的代码通过工具生成；
编写controller，在里面判断实际情况是否达到了API对象的声明情况，如果未达到，就要进行实际业务处理，而这也是controller的通用做法；
实际编码过程并不负载，动手编写的文件如下：

├── controller.go
├── main.go
└── pkg├── apis│   └── bolingcavalry│       ├── register.go│       └── v1│           ├── doc.go│           ├── register.go│           └── types.go└── signals├── signal.go├── signal_posix.go└── signal_windows.go

以上就是k8s自定义controller的整个开发过程，希望在您的开发过程中本文能提供一些参考；

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