Golang原生rpc(rpc服务端源码解读) Golang原生rpc(rpc服务端源码解读

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

【Golang原生rpc(rpc服务端源码解读)】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false 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 //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 = https://www.it610.com/article/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