kubernetes之operator开发controller-runtime源码分析

一、概述

Operator 的运行机制是作为自定义扩展资源注册到Controller Manager，通过List-Watch的方式监听对应资源的变化。controller-runtime 是 Kubernetes 社区提供可供快速搭建一套 实现了controller 功能的工具，对client-go进行了封装，用户无需自行实现Controller的功能了，只需关注Reconciler即可。

二、main函数入口

func main() {
   
    // 1.构建controllerManager
	mgr, err := ctrl.NewManager(ctrl.GetConfigOrDie(), ctrl.Options{
   
		Scheme:                 scheme,
		MetricsBindAddress:     metricsAddr,
		Port:                   9443,
		HealthProbeBindAddress: probeAddr,
		LeaderElection:         enableLeaderElection,
		LeaderElectionID:       "1de8eaa9.demo.kubebuilder.io",
	})
    // 2.将reconciler添加到controllerManager中
	if err = (&controllers.MyNginxReconciler{
   
		Client: mgr.GetClient(),
		Scheme: mgr.GetScheme(),
	}).SetupWithManager(mgr); err != nil {
   
		setupLog.Error(err, "unable to create controller", "controller", "MyNginx")
		os.Exit(1)
	}
	//+kubebuilder:scaffold:builder
	setupLog.Info("starting manager")
	// 3.启动controllerManager
	if err := mgr.Start(ctrl.SetupSignalHandler()); err != nil {
   
		setupLog.Error(err, "problem running manager")
		os.Exit(1)
	}
}

2.1 SetupWithManager

SetupWithManager做了三件事情：

1. 构建一个controller，并加入到controllerManager中
2. 为该controller设置watch对象，也就是myappv1.MyNginxUss{}
3. 为该controller设置Reconciler，也就是MemcachedReconciler

// SetupWithManager sets up the controller with the Manager.
func (r *MyNginxReconciler) SetupWithManager(mgr ctrl.Manager) error {
   
	return ctrl.NewControllerManagedBy(mgr).
	    //设置监听对象
		For(&myappv1.MyNginxUss{
   }). 
		//创建controller
		Complete(r)
}

// Complete builds the Application Controller.
func (blder *Builder) Complete(r reconcile.Reconciler) error {
   
	_, err := blder.Build(r)
	return err
}

// Build builds the Application Controller and returns the Controller it created.
func (blder *Builder) Build(r reconcile.Reconciler) (controller.Controller, error) {
   
	if r == nil {
   
		return nil, fmt.Errorf("must provide a non-nil Reconciler")
	}
	if blder.mgr == nil {
   
		return nil, fmt.Errorf("must provide a non-nil Manager")
	}
	if blder.forInput.err != nil {
   
		return nil, blder.forInput.err
	}
	// Checking the reconcile type exist or not
	if blder.forInput.object == nil {
   
		return nil, fmt.Errorf("must provide an object for reconciliation")
	}

	// Set the ControllerManagedBy
	//创建controller
	if err := blder.doController(r); err != nil {
   
		return nil, err
	}

	// Set the Watch
	//创建watch
	if err := blder.doWatch(); err != nil {
   
		return nil, err
	}

	return blder.ctrl, nil
}

先看doController()：

func (blder *Builder) doController(r reconcile.Reconciler) error {
   
	globalOpts := blder.mgr.GetControllerOptions()

	ctrlOptions := blder.ctrlOptions
	if ctrlOptions.Reconciler == nil {
   
	    //设置reconciler
		ctrlOptions.Reconciler = r
	}
    //省略代码
	......

	// Build the controller and return.
	//创建controller
	blder.ctrl, err = newController(blder.getControllerName(gvk), blder.mgr, ctrlOptions)
	return err
}

//newController就是调用这个方法
// New returns a new Controller registered with the Manager.  The Manager will ensure that shared Caches have
// been synced before the Controller is Started.
func New(name string, mgr manager.Manager, options Options) (Controller, error) {
   
    //创建了controller
	c, err := NewUnmanaged(name, mgr, options)
	if err != nil {
   
		return nil, err
	}

	// Add the controller as a Manager components
	//将controller加入到Manage中
	return c, mgr.Add(c)