> For the complete documentation index, see [llms.txt](https://eddycjy.gitbook.io/golang/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://eddycjy.gitbook.io/golang/di-4-ke-grpc/grpc-http.md).

# 4.7 让你的服务同时提供 HTTP 接口

项目地址：<https://github.com/EDDYCJY/go-grpc-example>

## 前言

* 接口需要提供给其他业务组访问，但是 RPC 协议不同无法内调，对方问能否走 HTTP 接口，怎么办？
* 微信（公众号、小程序）等第三方回调接口只支持 HTTP 接口，怎么办

我相信你在实际工作中都会遇到如上问题，在 gRPC 中都是有解决方案的，本章节将会进行介绍 🤔

## 为什么可以同时提供 HTTP 接口

关键一点，gRPC 的协议是基于 HTTP/2 的，因此应用程序能够在单个 TCP 端口上提供 HTTP/1.1 和 gRPC 接口服务（两种不同的流量）

## 怎么同时提供 HTTP 接口

### 检测协议

```
if r.ProtoMajor == 2 && strings.Contains(r.Header.Get("Content-Type"), "application/grpc") {
    server.ServeHTTP(w, r)
} else {
    mux.ServeHTTP(w, r)
}
```

### 流程

1. 检测请求协议是否为 HTTP/2
2. 判断 Content-Type 是否为 application/grpc（gRPC 的默认标识位）
3. 根据协议的不同转发到不同的服务处理

## gRPC

### TLS

在前面的章节，为了便于展示因此没有简单封装

在本节需复用代码，重新封装了，可详见：[go-grpc-example](https://github.com/EDDYCJY/go-grpc-example/tree/master/pkg/gtls)

### 目录结构

新建 simple\_http\_client、simple\_http\_server 目录，目录结构如下：

```
go-grpc-example
├── client
│   ├── simple_client
│   ├── simple_http_client
│   └── stream_client
├── conf
├── pkg
│   └── gtls
├── proto
├── server
│   ├── simple_http_server
│   ├── simple_server
│   └── stream_server
```

### Server

在 simple\_http\_server 目录下新建 server.go，写入文件内容：

```
package main

import (
    "context"
    "log"
    "net/http"
    "strings"

    "github.com/EDDYCJY/go-grpc-example/pkg/gtls"
    pb "github.com/EDDYCJY/go-grpc-example/proto"

    "google.golang.org/grpc"
)

type SearchService struct{}

func (s *SearchService) Search(ctx context.Context, r *pb.SearchRequest) (*pb.SearchResponse, error) {
    return &pb.SearchResponse{Response: r.GetRequest() + " HTTP Server"}, nil
}

const PORT = "9003"

func main() {
    certFile := "../../conf/server/server.pem"
    keyFile := "../../conf/server/server.key"
    tlsServer := gtls.Server{
        CertFile: certFile,
        KeyFile:  keyFile,
    }

    c, err := tlsServer.GetTLSCredentials()
    if err != nil {
        log.Fatalf("tlsServer.GetTLSCredentials err: %v", err)
    }

    mux := GetHTTPServeMux()

    server := grpc.NewServer(grpc.Creds(c))
    pb.RegisterSearchServiceServer(server, &SearchService{})

    http.ListenAndServeTLS(":"+PORT,
        certFile,
        keyFile,
        http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            if r.ProtoMajor == 2 && strings.Contains(r.Header.Get("Content-Type"), "application/grpc") {
                server.ServeHTTP(w, r)
            } else {
                mux.ServeHTTP(w, r)
            }

            return
        }),
    )
}

func GetHTTPServeMux() *http.ServeMux {
    mux := http.NewServeMux()
    mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        w.Write([]byte("eddycjy: go-grpc-example"))
    })

    return mux
}
```

* http.NewServeMux：创建一个新的 ServeMux，ServeMux 本质上是一个路由表。它默认实现了 ServeHTTP，因此返回 Handler 后可直接通过 HandleFunc 注册 pattern 和处理逻辑的方法
* http.ListenAndServeTLS：可简单的理解为提供监听 HTTPS 服务的方法，重点的协议判断转发，也在这里面

其实，你理解后就会觉得很简单，核心步骤：判断 -> 转发 -> 响应。我们改变了前两步的默认逻辑，仅此而已

### Client

在 simple\_http\_server 目录下新建 client.go，写入文件内容：

```
package main

import (
    "context"
    "log"

    "google.golang.org/grpc"

    "github.com/EDDYCJY/go-grpc-example/pkg/gtls"
    pb "github.com/EDDYCJY/go-grpc-example/proto"
)

const PORT = "9003"

func main() {
    tlsClient := gtls.Client{
        ServerName: "go-grpc-example",
        CertFile:   "../../conf/server/server.pem",
    }
    c, err := tlsClient.GetTLSCredentials()
    if err != nil {
        log.Fatalf("tlsClient.GetTLSCredentials err: %v", err)
    }

    conn, err := grpc.Dial(":"+PORT, grpc.WithTransportCredentials(c))
    if err != nil {
        log.Fatalf("grpc.Dial err: %v", err)
    }
    defer conn.Close()

    client := pb.NewSearchServiceClient(conn)
    resp, err := client.Search(context.Background(), &pb.SearchRequest{
        Request: "gRPC",
    })
    if err != nil {
        log.Fatalf("client.Search err: %v", err)
    }

    log.Printf("resp: %s", resp.GetResponse())
}
```

## 验证

### gRPC Client

```
$ go run client.go 
2018/10/04 14:56:56 resp: gRPC HTTP Server
```

### HTTP/1.1 访问

![image](https://image.eddycjy.com/1d92cb9e949e32eef7f8a64a6a77deb9.jpg)

## 总结

通过本章节，表面上完成了同端口提供双服务的功能，但实际上，应该是加深了 HTTP/2 的理解和使用，这才是本质

## 拓展

如果你有一个需求，是要**同时提供** RPC 和 RESTful JSON API 两种接口的，不要犹豫，点进去：[gRPC + gRPC Gateway 实践](https://segmentfault.com/a/1190000013339403)

## 问题

你以为这个方案就万能了吗，不。Envoy Proxy 的支持就不完美，无法同时监听一个端口的两种流量 😤

## 参考

### 本系列示例代码

* [go-grpc-example](https://github.com/EDDYCJY/go-grpc-example)


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