一、RPC原理
1、RPC框架由來
單體應用體量越來越大，代碼不好維護和管理，所以就產生了微服務架構，按照公共或功能模塊拆分為一個個獨立的服務，然后各獨立的服務之間可以相互呼叫，
微服務之間相互呼叫，該如何實作？
首先要解決下面5個問題：
1、如何規定遠程呼叫的語法？
2、如何傳遞引數？
3、如何表示資料？
4、如何知道一個服務端都實作了哪些遠程呼叫？從哪個埠可以訪問這個遠程呼叫？
5、發生了錯誤、重傳、丟包、性能等問題怎么辦？
大家可能都寫過socket或則http通信，簡單的client訪問server的模式，認為通過這個就可以解決服務之間的相互呼叫了，但是考慮下上面5個問題，處理起來就不是那么容易的事情了，非個人可以完成的作業，
于是就誕生了RPC框架，讓我們不用管底層實作，簡單好用：
2、RPC框架原理
當客戶端的應用想發起一個遠程呼叫時，它實際是呼叫客戶端的 Stub，它負責將呼叫的介面、方法和引數，通過約定的協議規范進行編碼，并通過本地的 RPCRuntime 進行傳輸，將呼叫網路包發送到服務器，服務器端的 RPCRuntime 收到請求后，交給服務器端的 Stub 進行解碼，然后呼叫服務端的方法，服務端執行方法，回傳結果，服務器端的 Stub 將回傳結果編碼后，發送給客戶端，客戶端的 RPCRuntime 收到結果，發給客戶端的 Stub 解碼得到結果，回傳給客戶端，
1、對于客戶端而言，這些程序是透明的，就像本地呼叫一樣；對于服務端而言，專注于業務邏輯的處理就可以了，
2、對于 Stub 層，處理雙方約定好的語法、語意、封裝、解封裝，
3、對于 RPCRuntime，主要處理高性能的傳輸，以及網路的錯誤和例外，
來看一下RPC框架是如何解決上面5個問題的：1、2、3的問題可以由Stub層解決，4的問題可以由服務注冊和發布解決，5的問題可以由RPCRuntime解決，
個人理解Stub層的語法、語意約定現在常用的都是協議檔案方式，流行的有xml、json、protocol buffers等等，它們各自都帶有自己特有的封裝解封裝方法，封裝解封裝主要解決兩個問題：
1、壓縮資料，減少傳輸資料量；
2、資料結構中欄位的映射關系；
二、GRPC原理
gRPC 是一個高性能、開源和通用的 RPC 框架，面向移動和 HTTP/2 設計，目前提供 C、Java 和 Go 語言版本，分別是：grpc, grpc-java, grpc-go. 其中 C 版本支持 C, C++, Node.js, Python, Ruby, Objective-C, PHP 和 C# 支持，
本文以GO語言版本講解
1、Golang安裝GRPC
詳細安裝連接
2、protocol buffer原理文章
文章1
文章2
3、grpc-go github地址:
github倉庫
godoc檔案
grpc-go 的Stub層協議約定問題通過.proto檔案約定好服務介面、引數等，通過工具protoc-gen-go生成客戶端和服務端共用的對照表，想生成什么語言檔案就用相應的插件，這樣就實作了跨語言，
生成GO語言檔案使用命令如下：
protoc --go_out=plugins=grpc:. *.proto
gRPC RPCRuntime層基于HTTP/2設計，帶來諸如雙向流、流控、頭部壓縮、單 TCP 連接上的多復用請求等特性，
GRPC Server端啟動
1、整體啟動程序
func main() {
//決議運行引數
flag.Parse()
//配置監聽協議、地址、埠
lis, err := net.Listen("tcp", fmt.Sprintf("localhost:%d", *port))
if err != nil {
log.Fatalf("failed to listen: %v", err)
}
//grpc額外的服務配置，這里主要是需不需要加密
var opts []grpc.ServerOption
if *tls {
if *certFile == "" {
*certFile = testdata.Path("server1.pem")
}
if *keyFile == "" {
*keyFile = testdata.Path("server1.key")
}
creds, err := credentials.NewServerTLSFromFile(*certFile, *keyFile)
if err != nil {
log.Fatalf("Failed to generate credentials %v", err)
}
opts = []grpc.ServerOption{grpc.Creds(creds)}
}
//grpc服務初始化，系結一些配置引數
grpcServer := grpc.NewServer(opts...)
//把.proto檔案中定義的介面API實作注冊到grpc服務上，方便呼叫
pb.RegisterRouteGuideServer(grpcServer, newServer())
//grpc服務啟動，開始監聽
grpcServer.Serve(lis)
}
2、Serve函式
關鍵處理就是一個for回圈，如果Accept() 回傳錯誤，并且錯誤是臨時性的，那么會有重試，重試時間以5ms翻倍增長，直到1s，
for {
rawConn, err := lis.Accept()
//錯誤處理
if err != nil {
if ne, ok := err.(interface {
Temporary() bool
}); ok && ne.Temporary() {
if tempDelay == 0 {
tempDelay = 5 * time.Millisecond
} else {
tempDelay *= 2
}
if max := 1 * time.Second; tempDelay > max {
tempDelay = max
}
s.mu.Lock()
s.printf("Accept error: %v; retrying in %v", err, tempDelay)
s.mu.Unlock()
timer := time.NewTimer(tempDelay)
select {
case <-timer.C:
case <-s.quit.Done():
timer.Stop()
return nil
}
continue
}
s.mu.Lock()
s.printf("done serving; Accept = %v", err)
s.mu.Unlock()
if s.quit.HasFired() {
return nil
}
return err
}
tempDelay = 0
// Start a new goroutine to deal with rawConn so we don't stall this Accept
// loop goroutine.
//
// Make sure we account for the goroutine so GracefulStop doesn't nil out
// s.conns before this conn can be added.
s.serveWG.Add(1)
//重新啟動一個goroutine處理accept的連接
go func() {
s.handleRawConn(rawConn)
s.serveWG.Done()
}()
}
3、handleRawConn函式
主要作用就是獲取一個服務端的Transport，并開一個goroutine等待處理stream，里面會涉及到呼叫注冊的方法，
st := s.newHTTP2Transport(conn, authInfo)
if st == nil {
return
}
rawConn.SetDeadline(time.Time{})
if !s.addConn(st) {
return
}
go func() {
s.serveStreams(st)
s.removeConn(st)
}()
GRPC Client端啟動
1、建立連接和系結實作的介面
//決議運行引數
flag.Parse()
//連接的一些配置，主要是加密，安全、阻塞
var opts []grpc.DialOption
if *tls {
if *caFile == "" {
*caFile = testdata.Path("ca.pem")
}
creds, err := credentials.NewClientTLSFromFile(*caFile, *serverHostOverride)
if err != nil {
log.Fatalf("Failed to create TLS credentials %v", err)
}
opts = append(opts, grpc.WithTransportCredentials(creds))
} else {
opts = append(opts, grpc.WithInsecure())
}
opts = append(opts, grpc.WithBlock())
//建立一個連接
conn, err := grpc.Dial(*serverAddr, opts...)
if err != nil {
log.Fatalf("fail to dial: %v", err)
}
defer conn.Close()
//創建一個實作了.proto檔案定義的介面API的Client
client := pb.NewRouteGuideClient(conn)
2、Client呼叫方式
Unary RPC: 一元RPC
func (c *routeGuideClient) GetFeature(ctx context.Context, in *Point, opts ...grpc.CallOption) (*Feature, error) {
out := new(Feature)
err := c.cc.Invoke(ctx, "/routeguide.RouteGuide/GetFeature", in, out, opts...)
if err != nil {
return nil, err
}
return out, nil
}
// printFeature gets the feature for the given point.
func printFeature(client pb.RouteGuideClient, point *pb.Point) {
log.Printf("Getting feature for point (%d, %d)", point.Latitude, point.Longitude)
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()
feature, err := client.GetFeature(ctx, point)
if err != nil {
log.Fatalf("%v.GetFeatures(_) = _, %v: ", client, err)
}
log.Println(feature)
}
// GetFeature returns the feature at the given point.
func (s *routeGuideServer) GetFeature(ctx context.Context, point *pb.Point) (*pb.Feature, error) {
for _, feature := range s.savedFeatures {
if proto.Equal(feature.Location, point) {
return feature, nil
}
}
// No feature was found, return an unnamed feature
return &pb.Feature{Location: point}, nil
}
Server-Side streaming RPC: 服務端流式RPC
func (c *routeGuideClient) ListFeatures(ctx context.Context, in *Rectangle, opts ...grpc.CallOption) (RouteGuide_ListFeaturesClient, error) {
stream, err := c.cc.NewStream(ctx, &_RouteGuide_serviceDesc.Streams[0], "/routeguide.RouteGuide/ListFeatures", opts...)
if err != nil {
return nil, err
}
x := &routeGuideListFeaturesClient{stream}
if err := x.ClientStream.SendMsg(in); err != nil {
return nil, err
}
if err := x.ClientStream.CloseSend(); err != nil {
return nil, err
}
return x, nil
}
// printFeatures lists all the features within the given bounding Rectangle.
func printFeatures(client pb.RouteGuideClient, rect *pb.Rectangle) {
log.Printf("Looking for features within %v", rect)
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()
stream, err := client.ListFeatures(ctx, rect)
if err != nil {
log.Fatalf("%v.ListFeatures(_) = _, %v", client, err)
}
for {
feature, err := stream.Recv()
if err == io.EOF {
break
}
if err != nil {
log.Fatalf("%v.ListFeatures(_) = _, %v", client, err)
}
log.Println(feature)
}
}
// ListFeatures lists all features contained within the given bounding Rectangle.
func (s *routeGuideServer) ListFeatures(rect *pb.Rectangle, stream pb.RouteGuide_ListFeaturesServer) error {
for _, feature := range s.savedFeatures {
if inRange(feature.Location, rect) {
if err := stream.Send(feature); err != nil {
return err
}
}
}
return nil
}
Client-Side streaming RPC: 客戶端流式RPC
func (c *routeGuideClient) RecordRoute(ctx context.Context, opts ...grpc.CallOption) (RouteGuide_RecordRouteClient, error) {
stream, err := c.cc.NewStream(ctx, &_RouteGuide_serviceDesc.Streams[1], "/routeguide.RouteGuide/RecordRoute", opts...)
if err != nil {
return nil, err
}
x := &routeGuideRecordRouteClient{stream}
return x, nil
}
// runRecordRoute sends a sequence of points to server and expects to get a RouteSummary from server.
func runRecordRoute(client pb.RouteGuideClient) {
// Create a random number of random points
r := rand.New(rand.NewSource(time.Now().UnixNano()))
pointCount := int(r.Int31n(100)) + 2 // Traverse at least two points
var points []*pb.Point
for i := 0; i < pointCount; i++ {
points = append(points, randomPoint(r))
}
log.Printf("Traversing %d points.", len(points))
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()
stream, err := client.RecordRoute(ctx)
if err != nil {
log.Fatalf("%v.RecordRoute(_) = _, %v", client, err)
}
for _, point := range points {
if err := stream.Send(point); err != nil {
log.Fatalf("%v.Send(%v) = %v", stream, point, err)
}
}
reply, err := stream.CloseAndRecv()
if err != nil {
log.Fatalf("%v.CloseAndRecv() got error %v, want %v", stream, err, nil)
}
log.Printf("Route summary: %v", reply)
}
// RecordRoute records a route composited of a sequence of points.
//
// It gets a stream of points, and responds with statistics about the "trip":
// number of points, number of known features visited, total distance traveled, and
// total time spent.
func (s *routeGuideServer) RecordRoute(stream pb.RouteGuide_RecordRouteServer) error {
var pointCount, featureCount, distance int32
var lastPoint *pb.Point
startTime := time.Now()
for {
point, err := stream.Recv()
if err == io.EOF {
endTime := time.Now()
return stream.SendAndClose(&pb.RouteSummary{
PointCount: pointCount,
FeatureCount: featureCount,
Distance: distance,
ElapsedTime: int32(endTime.Sub(startTime).Seconds()),
})
}
if err != nil {
return err
}
pointCount++
for _, feature := range s.savedFeatures {
if proto.Equal(feature.Location, point) {
featureCount++
}
}
if lastPoint != nil {
distance += calcDistance(lastPoint, point)
}
lastPoint = point
}
}
Bidirectional streaming RPC : 雙向流式RPC
func (c *routeGuideClient) RouteChat(ctx context.Context, opts ...grpc.CallOption) (RouteGuide_RouteChatClient, error) {
stream, err := c.cc.NewStream(ctx, &_RouteGuide_serviceDesc.Streams[2], "/routeguide.RouteGuide/RouteChat", opts...)
if err != nil {
return nil, err
}
x := &routeGuideRouteChatClient{stream}
return x, nil
}
// runRouteChat receives a sequence of route notes, while sending notes for various locations.
func runRouteChat(client pb.RouteGuideClient) {
notes := []*pb.RouteNote{
{Location: &pb.Point{Latitude: 0, Longitude: 1}, Message: "First message"},
{Location: &pb.Point{Latitude: 0, Longitude: 2}, Message: "Second message"},
{Location: &pb.Point{Latitude: 0, Longitude: 3}, Message: "Third message"},
{Location: &pb.Point{Latitude: 0, Longitude: 1}, Message: "Fourth message"},
{Location: &pb.Point{Latitude: 0, Longitude: 2}, Message: "Fifth message"},
{Location: &pb.Point{Latitude: 0, Longitude: 3}, Message: "Sixth message"},
}
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()
stream, err := client.RouteChat(ctx)
if err != nil {
log.Fatalf("%v.RouteChat(_) = _, %v", client, err)
}
waitc := make(chan struct{})
go func() {
for {
in, err := stream.Recv()
if err == io.EOF {
// read done.
close(waitc)
return
}
if err != nil {
log.Fatalf("Failed to receive a note : %v", err)
}
log.Printf("Got message %s at point(%d, %d)", in.Message, in.Location.Latitude, in.Location.Longitude)
}
}()
for _, note := range notes {
if err := stream.Send(note); err != nil {
log.Fatalf("Failed to send a note: %v", err)
}
}
stream.CloseSend()
<-waitc
}
// RouteChat receives a stream of message/location pairs, and responds with a stream of all
// previous messages at each of those locations.
func (s *routeGuideServer) RouteChat(stream pb.RouteGuide_RouteChatServer) error {
for {
in, err := stream.Recv()
if err == io.EOF {
return nil
}
if err != nil {
return err
}
key := serialize(in.Location)
s.mu.Lock()
s.routeNotes[key] = append(s.routeNotes[key], in)
// Note: this copy prevents blocking other clients while serving this one.
// We don't need to do a deep copy, because elements in the slice are
// insert-only and never modified.
rn := make([]*pb.RouteNote, len(s.routeNotes[key]))
copy(rn, s.routeNotes[key])
s.mu.Unlock()
for _, note := range rn {
if err := stream.Send(note); err != nil {
return err
}
}
}
}
Client 連接底層兩個主要方法
1、Invoke函式
newClientStream：獲取傳輸層 Trasport 并組合封裝到 ClientStream 中回傳，在這塊會涉及負載均衡、超時控制、 Encoding、 Stream 的動作，與服務端基本一致的行為，
cs.SendMsg：發送 RPC 請求出去，但其并不承擔等待回應的功能，
cs.RecvMsg：阻塞等待接受到的 RPC 方法回應結果，
// Invoke sends the RPC request on the wire and returns after response is
// received. This is typically called by generated code.
//
// All errors returned by Invoke are compatible with the status package.
func (cc *ClientConn) Invoke(ctx context.Context, method string, args, reply interface{}, opts ...CallOption) error {
// allow interceptor to see all applicable call options, which means those
// configured as defaults from dial option as well as per-call options
opts = combine(cc.dopts.callOptions, opts)
if cc.dopts.unaryInt != nil {
return cc.dopts.unaryInt(ctx, method, args, reply, cc, invoke, opts...)
}
return invoke(ctx, method, args, reply, cc, opts...)
}
func invoke(ctx context.Context, method string, req, reply interface{}, cc *ClientConn, opts ...CallOption) error {
cs, err := newClientStream(ctx, unaryStreamDesc, cc, method, opts...)
if err != nil {
return err
}
if err := cs.SendMsg(req); err != nil {
return err
}
return cs.RecvMsg(reply)
}
2、NewStream函式
// NewStream creates a new Stream for the client side. This is typically
// called by generated code. ctx is used for the lifetime of the stream.
//
// To ensure resources are not leaked due to the stream returned, one of the following
// actions must be performed:
//
// 1. Call Close on the ClientConn.
// 2. Cancel the context provided.
// 3. Call RecvMsg until a non-nil error is returned. A protobuf-generated
// client-streaming RPC, for instance, might use the helper function
// CloseAndRecv (note that CloseSend does not Recv, therefore is not
// guaranteed to release all resources).
// 4. Receive a non-nil, non-io.EOF error from Header or SendMsg.
//
// If none of the above happen, a goroutine and a context will be leaked, and grpc
// will not call the optionally-configured stats handler with a stats.End message.
func (cc *ClientConn) NewStream(ctx context.Context, desc *StreamDesc, method string, opts ...CallOption) (ClientStream, error) {
// allow interceptor to see all applicable call options, which means those
// configured as defaults from dial option as well as per-call options
opts = combine(cc.dopts.callOptions, opts)
if cc.dopts.streamInt != nil {
return cc.dopts.streamInt(ctx, desc, cc, method, newClientStream, opts...)
}
return newClientStream(ctx, desc, cc, method, opts...)
}
總結
gRPC的優點和缺點：
優點：
1、protobuf二進制訊息，性能好/效率高（空間和時間效率都很不錯）；
2、proto檔案生成目標代碼，簡單易用；
3、序列化反序列化直接對應程式中的資料類，不需要決議后在進行映射(XML,JSON都是這種方式)；
4、支持向前兼容（新加欄位采用默認值）和向后兼容（忽略新加欄位），簡化升級；
5、支持多種語言（可以把proto檔案看做IDL檔案）；
6、Netty等一些框架集成；
缺點：
1、GRPC尚未提供連接池，需要自行實作；
2、尚未提供“服務發現”、“負載均衡”機制；
3、因為基于HTTP2，絕大部多數HTTP Server、Nginx都尚不支持，即Nginx不能將GRPC請求作為HTTP請求來負載均衡，而是作為普通的TCP請求，（nginx1.9版本已支持）；
4、Protobuf二進制可讀性差（貌似提供了Text_Fromat功能，沒用過）；
5、默認不具備動態特性（可以通過動態定義生成訊息型別或者動態編譯支持）；
參考資料
1.從實踐到原理，帶你參透GRPC.
2.極客時間：趣談網路協議32-36講.
轉載請註明出處，本文鏈接：https://www.uj5u.com/houduan/36311.html
標籤：Go
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