pilot-discover代码阅读.md

// 在实例化一个变量之前，可以传入函数作用于它。pilot中的addFlags函数使用了类似“过滤器”的做法：
// NewPilotArgs constructs pilotArgs with default values.
func NewPilotArgs(initFuncs ...func(*PilotArgs)) *PilotArgs {
	p := &PilotArgs{}

	// Apply Default Values.
	p.applyDefaults()

	// Apply custom initialization functions.
	for _, fn := range initFuncs {
		fn(p)
	}
  ...

	serverArgs = bootstrap.NewPilotArgs(func(p *bootstrap.PilotArgs) {
		// Set Defaults
		p.CtrlZOptions = ctrlz.DefaultOptions()
		// TODO replace with mesh config?
		p.InjectionOptions = bootstrap.InjectionOptions{
			InjectionDirectory: "./var/lib/istio/inject",
		}
	})
  ...

// ledger 保存了map 的之前状态，具有三个特征：
// 1. every unique state of the map is given a unique hash
// 2. prior states of the map are retained for a fixed period of time
// 2. given a previous hash, we can retrieve a previous state from the map, if it is still retained.

// 监控文件变化
// NewWatcher return with a FileWatcher instance that implemented with fsnotify.
func NewWatcher() FileWatcher {
	return &fileWatcher{
		workers: map[string]*workerState{},

		// replaceable functions for tests
		funcs: &patchTable{
			newWatcher: fsnotify.NewWatcher,
			addWatcherPath: func(watcher *fsnotify.Watcher, path string) error {
				return watcher.Add(path)
			},
		},
	}
}

// 写时复制，先分配好list的容量，然后append，节省内存分配时间
func (c *ControllerHandlers) AppendWorkloadHandler(f func(*WorkloadInstance, Event)) {
	// Copy on write.
	c.mutex.Lock()
	handlers := make([]func(*WorkloadInstance, Event), 0, len(c.workloadHandlers)+1)
	handlers = append(handlers, c.workloadHandlers...)
	handlers = append(handlers, f)
	c.workloadHandlers = handlers
	c.mutex.Unlock()
}

// istio\pilot\pkg\serviceregistry\aggregate\controller.go
// 区分servicehandler workloadhandler instancehandler,后者是前两者的汇总
// Controller defines an event controller loop.  Proxy agent registers itself
// with the controller loop and receives notifications on changes to the
// service topology or changes to the configuration artifacts.
//
// The controller guarantees the following consistency requirement: registry
// view in the controller is as AT LEAST as fresh as the moment notification
// arrives, but MAY BE more fresh (e.g. "delete" cancels an "add" event).  For
// example, an event for a service creation will see a service registry without
// the service if the event is immediately followed by the service deletion
// event.
//
// Handlers execute on the single worker queue in the order they are appended.
// Handlers receive the notification event and the associated object.  Note
// that all handlers must be appended before starting the controller.
type Controller interface {
	// AppendServiceHandler notifies about changes to the service catalog.
	AppendServiceHandler(f func(*Service, Event))

	// AppendWorkloadHandler notifies about changes to workloads. This differs from InstanceHandler,
	// which deals with service instances (the result of a merge of Service and Workload)
	AppendWorkloadHandler(f func(*WorkloadInstance, Event))

	// Run until a signal is received
	Run(stop <-chan struct{})

	// HasSynced returns true after initial cache synchronization is complete
	HasSynced() bool
}

func newDiscoveryCommand() *cobra.Command {
	return &cobra.Command{
		Use:   "discovery",
		Short: "Start Istio proxy discovery service.",
	        // 注意 args 0 , cobra中分 command,arguments,flags 
        	Args:  cobra.ExactArgs(0),
		PreRunE:...
...