26.使用中间件的方式包装日志输出

package Services

import (
    "context"
    "fmt"
    "github.com/go-kit/kit/endpoint"
    "github.com/go-kit/kit/log"
    "golang.org/x/time/rate"
    "gomicro/utils"
    "strconv"
)

type UserRequest struct { //封装User请求结构体
    Uid    int `json:"uid"`
    Method string
}

type UserResponse struct {
    Result string `json:"result"`
}

//日志中间件,每一个service都应该有自己的日志中间件
func UserServiceLogMiddleware(logger log.Logger) endpoint.Middleware { //Middleware type Middleware func(Endpoint) Endpoint
    return func(next endpoint.Endpoint) endpoint.Endpoint { //Endpoint type Endpoint func(ctx context.Context, request interface{}) (response interface{}, err error)
        return func(ctx context.Context, request interface{}) (response interface{}, err error) {
            r := request.(UserRequest) //通过类型断言获取请求结构体
            logger.Log("method", r.Method, "event", "get user", "userid", r.Uid)
            return next(ctx, request)
        }
    }
}

//加入限流功能中间件
func RateLimit(limit *rate.Limiter) endpoint.Middleware { //Middleware type Middleware func(Endpoint) Endpoint
    return func(next endpoint.Endpoint) endpoint.Endpoint { //Endpoint type Endpoint func(ctx context.Context, request interface{}) (response interface{}, err error)
        return func(ctx context.Context, request interface{}) (response interface{}, err error) {
            if !limit.Allow() {
                return nil, utils.NewMyError(429, "toot many request")
            }
            return next(ctx, request)
        }
    }
}

func GenUserEnPoint(userService IUserService) endpoint.Endpoint {
    return func(ctx context.Context, request interface{}) (response interface{}, err error) {
        r := request.(UserRequest) //通过类型断言获取请求结构体
        result := "nothings"
        if r.Method == "GET" {
            result = userService.GetName(r.Uid) + strconv.Itoa(utils.ServicePort)

        } else if r.Method == "DELETE" {
            err := userService.DelUser(r.Uid)
            if err != nil {
                result = err.Error()
            } else {
                result = fmt.Sprintf("userid为%d的用户已删除", r.Uid)
            }
        }
        return UserResponse{Result: result}, nil
    }
}

package main

import (
    "flag"
    "fmt"
    kitlog "github.com/go-kit/kit/log"
    httptransport "github.com/go-kit/kit/transport/http"
    mymux "github.com/gorilla/mux"
    "golang.org/x/time/rate"
    "gomicro/Services"
    "gomicro/utils"
    "log"
    "net/http"
    "os"
    "os/signal"
    "strconv"
    "syscall"
)

func main() {
    go func() {}()
    go (func() {})()
    name := flag.String("name", "", "服务名称")
    port := flag.Int("port", 0, "服务端口")
    flag.Parse()
    if *name == "" {
        log.Fatal("请指定服务名")
    }
    if *port == 0 {
        log.Fatal("请指定端口")
    }
    var logger kitlog.Logger
    {
        logger = kitlog.NewLogfmtLogger(os.Stdout)
        logger = kitlog.WithPrefix(logger, "mykit", "1.0")
        logger = kitlog.WithPrefix(logger, "time", kitlog.DefaultTimestampUTC) //加上前缀时间
        logger = kitlog.WithPrefix(logger, "caller", kitlog.DefaultCaller)     //加上前缀，日志输出时的文件和第几行代码

    }
    utils.SetServiceNameAndPort(*name, *port) //设置服务名和端口

    user := Services.UserService{}
    limit := rate.NewLimiter(1, 5)
    endp := Services.RateLimit(limit)(Services.UserServiceLogMiddleware(logger)(Services.GenUserEnPoint(user)))
    /*我们分析一下上面这段代码Services.RateLimit(limit)返回一个Middware，type Middleware func(Endpoint) Endpoint
    也就是说这段代码的返回值必须是Endpoint类型
    type Endpoint func(ctx context.Context, request interface{}) (response interface{}, err error)
    才可以传入Middware (Services.UserServiceLogMiddleware(logger)(Services.GenUserEnPoint(user)))

    再拆分Services.UserServiceLogMiddleware(logger)也返回一个Middware，同理Services.GenUserEnPoint(user)必然是返回一个EndPoint，这里GenUserEnPoint(user)返回值是    func(ctx context.Context, request interface{}) (response interface{}, err error)所以是EndPoint类型
    那么(Services.UserServiceLogMiddleware(logger)是middleware,Services.GenUserEnPoint(user))值作为参数是Endpoint，返回值依然是一个Endpoint，这个返回值作为参数传递给了Services.RateLimit(limit)，Services.RateLimit(limit)也是一个Middware，所以这样写是成立的
    */

    options := []httptransport.ServerOption{
        httptransport.ServerErrorEncoder(Services.MyErrorEncoder),
    }

    serverHandler := httptransport.NewServer(endp, Services.DecodeUserRequest, Services.EncodeUserResponse, options...) //使用go kit创建server传入我们之前定义的两个解析函数

    r := mymux.NewRouter()
    //r.Handle(`/user/{uid:\d+}`, serverHandler) //这种写法支持多种请求方式
    r.Methods("GET", "DELETE").Path(`/user/{uid:\d+}`).Handler(serverHandler) //这种写法仅支持Get，限定只能Get请求
    r.Methods("GET").Path("/health").HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
        writer.Header().Set("Content-type", "application/json")
        writer.Write([]byte(`{"status":"ok"}`))
    })
    errChan := make(chan error)
    go func() {
        utils.RegService()                                                 //调用注册服务程序
        err := http.ListenAndServe(":"+strconv.Itoa(utils.ServicePort), r) //启动http服务
        if err != nil {
            log.Println(err)
            errChan <- err
        }
    }()
    go func() {
        sigChan := make(chan os.Signal)
        signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
        errChan <- fmt.Errorf("%s", <-sigChan)
    }()
    getErr := <-errChan
    utils.UnRegService()
    log.Println(getErr)
}