go-micro server 服务器

　　go-micro 支持很多通信协议：http、tcp、grpc等，支持的编码方式也很多有json、protobuf、bytes、jsonrpc等。也可以根据自己的需要实现通信协议和编码方式。go-micro 默认的通信协议是http，默认的编码方式是protobuf。

　　主要代码定义如下：

type Server interface {
	Options() Options
	Init(...Option) error
	Handle(Handler) error
	NewHandler(interface{}, ...HandlerOption) Handler
	NewSubscriber(string, interface{}, ...SubscriberOption) Subscriber
	Subscribe(Subscriber) error
	Register() error
	Deregister() error
	Start() error
	Stop() error
	String() string
}

type Message interface {
	Topic() string
	Payload() interface{}
	ContentType() string
}

type Request interface {
	Service() string
	Method() string
	ContentType() string
	Request() interface{}
	// indicates whether the request will be streamed
	Stream() bool
}

// Stream represents a stream established with a client.
// A stream can be bidirectional which is indicated by the request.
// The last error will be left in Error().
// EOF indicated end of the stream.
type Stream interface {
	Context() context.Context
	Request() Request
	Send(interface{}) error
	Recv(interface{}) error
	Error() error
	Close() error
}

type Option func(*Options)

type HandlerOption func(*HandlerOptions)

type SubscriberOption func(*SubscriberOptions)

　　

　　server 启动时会注册 handler ，即方法路由。注册机制是利用反射，把对象的信息完全提取出来，解析出结构体内的方法及方法的参数，保存到一个map内： map[结构体名称][方法信息集合]

func (s *rpcServer) Handle(h Handler) error {
	s.Lock()
	defer s.Unlock()

	if err := s.rpc.register(h.Handler()); err != nil {
		return err
	}

	s.handlers[h.Name()] = h

	return nil
}

　　

func (server *server) register(rcvr interface{}) error {
	server.mu.Lock()
	defer server.mu.Unlock()
	if server.serviceMap == nil {
		server.serviceMap = make(map[string]*service)
	}
	s := new(service)
	s.typ = reflect.TypeOf(rcvr)
	s.rcvr = reflect.ValueOf(rcvr)
	sname := reflect.Indirect(s.rcvr).Type().Name()
	if sname == "" {
		log.Fatal("rpc: no service name for type", s.typ.String())
	}
	if !isExported(sname) {
		s := "rpc Register: type " + sname + " is not exported"
		log.Log(s)
		return errors.New(s)
	}
	if _, present := server.serviceMap[sname]; present {
		return errors.New("rpc: service already defined: " + sname)
	}
	s.name = sname
	s.method = make(map[string]*methodType)

	// Install the methods
	for m := 0; m < s.typ.NumMethod(); m++ {
		method := s.typ.Method(m)
		if mt := prepareMethod(method); mt != nil {
			s.method[method.Name] = mt
		}
	}

	if len(s.method) == 0 {
		s := "rpc Register: type " + sname + " has no exported methods of suitable type"
		log.Log(s)
		return errors.New(s)
	}
	server.serviceMap[s.name] = s
	return nil
}

　　

type methodType struct {
	sync.Mutex  // protects counters
	method      reflect.Method
	ArgType     reflect.Type
	ReplyType   reflect.Type
	ContextType reflect.Type
	stream      bool
}

type service struct {
	name   string                 // name of service
	rcvr   reflect.Value          // receiver of methods for the service
	typ    reflect.Type           // type of the receiver
	method map[string]*methodType // registered methods
}

　　

　　路由信息处理完后，主要的工作就已经完成了，然后注册服务并启动服务，启动的服务是一个http的服务。启动流程如下：