grpc 实现

TODO

RegisterName

rpc.RegisterName("hello", new(hello.Hello))

// RegisterName is like Register but uses the provided name for the type
// instead of the receiver's concrete type.
func RegisterName(name string, rcvr interface{}) error {
	return DefaultServer.RegisterName(name, rcvr)
}

// DefaultServer is the default instance of *Server.
var DefaultServer = NewServer()

// NewServer returns a new Server.
func NewServer() *Server {
	return &Server{}
}

// Server represents an RPC Server.
type Server struct {
	serviceMap sync.Map   // map[string]*service
	reqLock    sync.Mutex // protects freeReq
	freeReq    *Request
	respLock   sync.Mutex // protects freeResp
	freeResp   *Response
}

// RegisterName is like Register but uses the provided name for the type
// instead of the receiver's concrete type.
func (server *Server) RegisterName(name string, rcvr interface{}) error {
	return server.register(rcvr, name, true)
}

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
}


func (server *Server) register(rcvr interface{}, name string, useName bool) error {
	s := new(service)
	s.typ = reflect.TypeOf(rcvr)
	s.rcvr = reflect.ValueOf(rcvr)
	sname := reflect.Indirect(s.rcvr).Type().Name()
	if useName {
		sname = name
	}
	if sname == "" {
		s := "rpc.Register: no service name for type " + s.typ.String()
		log.Print(s)
		return errors.New(s)
	}
	if !token.IsExported(sname) && !useName {
		s := "rpc.Register: type " + sname + " is not exported"
		log.Print(s)
		return errors.New(s)
	}
	s.name = sname

	// Install the methods
	s.method = suitableMethods(s.typ, true)

	if len(s.method) == 0 {
		str := ""

		// To help the user, see if a pointer receiver would work.
		//转换成指针类型再试试
		method := suitableMethods(reflect.PtrTo(s.typ), false)
		if len(method) != 0 {
			str = "rpc.Register: type " + sname + " has no exported methods of suitable type (hint: pass a pointer to value of that type)"
		} else {
			str = "rpc.Register: type " + sname + " has no exported methods of suitable type"
		}
		log.Print(str)
		return errors.New(str)
	}

	if _, dup := server.serviceMap.LoadOrStore(sname, s); dup {
		return errors.New("rpc: service already defined: " + sname)
	}
	return nil
}

suitableMethods

// suitableMethods returns suitable Rpc methods of typ, it will report
// error using log if reportErr is true.
func suitableMethods(typ reflect.Type, reportErr bool) map[string]*methodType {
	methods := make(map[string]*methodType)
	for m := 0; m < typ.NumMethod(); m++ {
		method := typ.Method(m)
		mtype := method.Type
		mname := method.Name
		// Method must be exported.
		if method.PkgPath != "" {
			continue
		}
		// Method needs three ins: receiver, *args, *reply.
		//func (h *Hello) Hello(req string, rep *string) error 
		if mtype.NumIn() != 3 {
			if reportErr {
				log.Printf("rpc.Register: method %q has %d input parameters; needs exactly three\n", mname, mtype.NumIn())
			}
			continue
		}
		// First arg need not be a pointer.
		argType := mtype.In(1)
		if !isExportedOrBuiltinType(argType) {
			if reportErr {
				log.Printf("rpc.Register: argument type of method %q is not exported: %q\n", mname, argType)
			}
			continue
		}
		// Second arg must be a pointer.
		replyType := mtype.In(2)
		if replyType.Kind() != reflect.Ptr {
			if reportErr {
				log.Printf("rpc.Register: reply type of method %q is not a pointer: %q\n", mname, replyType)
			}
			continue
		}
		// Reply type must be exported.
		if !isExportedOrBuiltinType(replyType) {
			if reportErr {
				log.Printf("rpc.Register: reply type of method %q is not exported: %q\n", mname, replyType)
			}
			continue
		}
		// Method needs one out.
		if mtype.NumOut() != 1 {
			if reportErr {
				log.Printf("rpc.Register: method %q has %d output parameters; needs exactly one\n", mname, mtype.NumOut())
			}
			continue
		}
		// The return type of the method must be error.
		if returnType := mtype.Out(0); returnType != typeOfError {
			if reportErr {
				log.Printf("rpc.Register: return type of method %q is %q, must be error\n", mname, returnType)
			}
			continue
		}
		methods[mname] = &methodType{method: method, ArgType: argType, ReplyType: replyType}
	}
	return methods
}

note

RegisterName其实就是通过reflect把数据结构的所有方法存到sync.map中