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创建rpc接口，需要几个条件
方法的类型是可输出的
方法的本身也是可输出的
方法必须有两个参数，必须是输出类型或者是内建类型
方法的第二个参数是指针类型
方法返回的类型为error
rpc服务原理分析
server端
服务注册
处理网络调用
服务注册 通过反射处理，将接口存入到map中，进行调用 注册服务两个方法
func Register (rcvr interface{}) error {}func RegisterName (rcvr interface{} , name string) error {}//指定注册的名称注册方法的源代码解读 首先，无论是Register还是RegisterName底层代码都是调用register方法，进行服务注册。 server.go register方法解读
func (server *Server) register(rcvr interface{}, name string, useName bool) error {//创建一个service实例s := new(service)s.typ = reflect.TypeOf(rcvr)s.rcvr = reflect.ValueOf(rcvr)sname := reflect.Indirect(s.rcvr).Type().Name()//如果服务名为空，则使用默认的服务名if useName {sname = name}if sname == "" {s := "rpc.Register: no service name for type " + s.typ.String()log.Print(s)return errors.New(s)}//判断方法名是否暴漏的，如果方法名不是暴露的，则会导致调用不成功，所以返回falseif !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//调用suitableMethods函数，进行返回接口，在suitableMethods中判断方法是否符合作为rpc接口的条件，如果符合，则进行添加到services中s.method = suitableMethods(s.typ, true)if len(s.method) == 0 {str := ""// To help the user, see if a pointer receiver would work.//如果方法绑定到结构体的地址上，使用reflect.TypeOf()是不会发现方法的，所以也要进行查找绑定到结构体地址上的方法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)}//判断服务接口是否已经注册。if _, dup := server.serviceMap.LoadOrStore(sname, s); dup {return errors.New("rpc: service already defined: " + sname)}return nil}suitableMethod方法解读
func suitableMethods(typ reflect.Type, reportErr bool) map[string]*methodType {//创建一个方法的切片methods := make(map[string]*methodType)for m := 0; m < typ.NumMethod(); m++ {method := typ.Method(m)mtype := method.Typemname := method.Name// Method must be exported.if method.PkgPath != "" {continue}// Method needs three ins: receiver, *args, *reply.//如果传入的参数，不为三个，则会报错，这里为什么是三个？//golang方法体中默认传入结构体实例，所以request,*response,结构体实例一共三个参数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.//判断第二个参数是否为指针，如果不为指针，则返回false。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.//返回结果是否为一个值，且为errorif 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}//将接口加入servicemethods[mname] = &methodType{method: method, ArgType: argType, ReplyType: replyType}}return methods}接收到请求后会不断的解析请求 解析请求的两个方法 readRequestHeader
func (server *Server) readRequestHeader(codec ServerCodec) (svc *service, mtype *methodType, req *Request, keepReading bool, err error) {// Grab the request header.//接收到请求，对请求进行编码req = server.getRequest()err = codec.ReadRequestHeader(req)if err != nil {req = nilif err == io.EOF || err == io.ErrUnexpectedEOF {return}err = errors.New("rpc: server cannot decode request: " + err.Error())return}// We read the header successfully. If we see an error now,// we can still recover and move on to the next request.keepReading = true//编码后的请求，进行间隔，所以只要进行将.的左右两边的数据进行分割，就能解码dot := strings.LastIndex(req.ServiceMethod, ".")if dot < 0 {err = errors.New("rpc: service/method request ill-formed: " + req.ServiceMethod)return}serviceName := req.ServiceMethod[:dot]methodName := req.ServiceMethod[dot+1:]// Look up the request.svci, ok := server.serviceMap.Load(serviceName)if !ok {err = errors.New("rpc: can't find service " + req.ServiceMethod)return}svc = svci.(*service)//获取到注册服务时，注册的接口mtype = svc.method[methodName]if mtype == nil {err = errors.New("rpc: can't find method " + req.ServiceMethod)}return}readRequest方法
func (server *Server) readRequest(codec ServerCodec) (service *service, mtype *methodType, req *Request, argv, replyv reflect.Value, keepReading bool, err error) {service, mtype, req, keepReading, err = server.readRequestHeader(codec)//调用上面的readRequestHeader方法，进行解码，并返返回接口数据if err != nil {if !keepReading {return}// discard bodycodec.ReadRequestBody(nil)return}// Decode the argument value.argIsValue := false // if true, need to indirect before calling.//判断传擦是否为指针，如果为指针，需要使用Elem()方法，进行指向结构体if mtype.ArgType.Kind() == reflect.Ptr {argv = reflect.New(mtype.ArgType.Elem())} else {argv = reflect.New(mtype.ArgType)argIsValue = true}// argv guaranteed to be a pointer now.if err = codec.ReadRequestBody(argv.Interface()); err != nil {return}if argIsValue {argv = argv.Elem()}replyv = reflect.New(mtype.ReplyType.Elem())switch mtype.ReplyType.Elem().Kind() {case reflect.Map:replyv.Elem().Set(reflect.MakeMap(mtype.ReplyType.Elem()))case reflect.Slice:replyv.Elem().Set(reflect.MakeSlice(mtype.ReplyType.Elem(), 0, 0))}return}call方法
func (s *service) call(server *Server, sending *sync.Mutex, wg *sync.WaitGroup, mtype *methodType, req *Request, argv, replyv reflect.Value, codec ServerCodec) {if wg != nil {defer wg.Done()}mtype.Lock()mtype.numCalls++mtype.Unlock()function := mtype.method.Func// Invoke the method, providing a new value for the reply.//调用call方法，并将参数转化为valueof型参数，returnValues := function.Call([]reflect.Value{s.rcvr, argv, replyv})// The return value for the method is an error.//将返回的error进行读取，转化为interface{}型errInter := returnValues[0].Interface()errmsg := ""if errInter != nil {//将error进行断言errmsg = errInter.(error).Error()}server.sendResponse(sending, req, replyv.Interface(), codec, errmsg)server.freeRequest(req)}注册的大概流程
根据反射，进行接口的获取
使用方法判断接口是否符合作为rpc接口的规范（有两个参数，第二个参数为指针，返回一个参数error）
如果不符合规范，将返回error，符合规范，将存入map，进行提供调用
接收请求的大概流程
首先，不断的接收数据流，并进行解码，解码之后为data.data，所以我们需要使用 . 作为分隔符，进行数据的截切和读取
将读取的数据在注册的map中进行查找，如果查找到，返回相关的service和其他数据
进行调用
感谢各位的阅读，以上就是“Golang原生rpc的原理是什么”的内容了，经过本文的学习后，相信大家对Golang原生rpc的原理是什么这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是编程网，小编将为大家推送更多相关知识点的文章，欢迎关注！
