下面由#Golang教學欄目跟大家介紹Golang實作簡單的API網關的方法，希望對需要的朋友有幫助！
在最近的一個專案中，採用了微服務架構-go-kit進行後端的開發。在微服務架構風格中，一個大應用被拆分成為了多個小的服務系統提供出來，這些小的系統他們可以自成體系，也就是說這些小系統可以擁有自己的資料庫，框架甚至語言等，因此我們需要設計一個API 網關(API Gataway)，其實網路上已經有較多現成的實作框架，但是本專案的需求是比較簡單的，因此將使用Golang自行實現。
API網關是伺服器，是系統的唯一入口。從物件導向設計的角度來看，它與外觀模式類似。 API閘道封裝了系統內部架構，為每個客戶端提供一個客製化的API。它可能還具有其它職責，如身份驗證、監控、負載平衡、快取、請求分片與管理、靜態回應處理。
用於實作API閘道的技術很多，大致上分為這麼幾類：
Nginx、Haproxy、…Netty、Servlet、…Spring Cloud Gateway、Zuul、Zuul2、…API閘道最基本的功能就是反向代理。其實作方式有很多，本文將基於標準函式庫net/http/httputil包中的ReverseProxy型別來實作一個簡單的反向代理程式。反向代理的實作主要涉及到func NewSingleHostReverseProxy(target *url.URL) *ReverseProxy和type ReverseProxy。
func NewSingleHostReverseProxy(target *url.URL) *ReverseProxy
// NewSingleHostReverseProxy returns a new ReverseProxy that routes// URLs to the scheme, host, and base path provided in target. If the// target's path is "/base" and the incoming request was for "/dir",// the target request will be for /base/dir.// NewSingleHostReverseProxy does not rewrite the Host header.// To rewrite Host headers, use ReverseProxy directly with a custom// Director policy.func NewSingleHostReverseProxy(target *url.URL) *ReverseProxy {
targetQuery := target.RawQuery
director := func(req *http.Request) {
req.URL.Scheme = target.Scheme
req.URL.Host = target.Host
req.URL.Path = singleJoiningSlash(target.Path, req.URL.Path)
if targetQuery == "" || req.URL.RawQuery == "" {
req.URL.RawQuery = targetQuery + req.URL.RawQuery } else {
req.URL.RawQuery = targetQuery + "&" + req.URL.RawQuery }
if _, ok := req.Header["User-Agent"]; !ok {
// explicitly disable User-Agent so it's not set to default value
req.Header.Set("User-Agent", "")
}
}
return &ReverseProxy{Director: director}}NewSingleHostReverseProxy傳回一個新的ReverseProxy，將URLs請求路由到targe的指定的 scheme, host, base path。
// ReverseProxy is an HTTP Handler that takes an incoming request and// sends it to another server, proxying the response back to the// client.type ReverseProxy struct {
// Director must be a function which modifies
// the request into a new request to be sent
// using Transport. Its response is then copied
// back to the original client unmodified.
// Director must not access the provided Request
// after returning.
Director func(*http.Request)
Transport http.RoundTripper
FlushInterval time.Duration
ErrorLog *log.Logger
BufferPool BufferPool // ModifyResponse is an optional function that modifies the
// Response from the backend. It is called if the backend
// returns a response at all, with any HTTP status code.
// If the backend is unreachable, the optional ErrorHandler is
// called without any call to ModifyResponse.
//
// If ModifyResponse returns an error, ErrorHandler is called
// with its error value. If ErrorHandler is nil, its default
// implementation is used.
ModifyResponse func(*http.Response) error
ErrorHandler func(http.ResponseWriter, *http.Request, error)}ReverseProxy類型有兩個重要的屬性，分別是Director和ModifyResponse，這兩個屬性都是函數類型，在接收到客戶端請求時，ServeHTTP函數首先呼叫Director函數對接受到的請求體進行修改，例如修改請求的目標位址、請求頭等；然後使用修改後的請求體發起新的請求，接收到回應後，呼叫ModifyResponse函數對回應進行修改，最後將修改後的回應體拷貝並回應給客戶端，這樣就實現了反向代理的整個流程。
在NewSingleHostReverseProxy中原始碼已經對傳入的URLs進行解析並且完成了Director的修改，我們只需要呼叫 NewSingleHostReverseProxy函數並且傳入目標伺服器的URL即可，一個簡單的反向代理就完成了啦。
實例程式碼只涉及微服務中
user與auth模組，可以依照實際需求自行修改部分
package mainimport (
"fmt"
"log"
"net/http"
"net/http/httputil"
"net/url"
"strings")type handle struct {
host string
port string}type Service struct {
auth *handle
user *handle}func (this *Service) ServeHTTP(w http.ResponseWriter, r *http.Request) {
var remote *url.URL if strings.Contains(r.RequestURI, "api/auth") {
remote, _ = url.Parse("http://" + this.auth.host + ":" + this.auth.port)
} else if strings.Contains(r.RequestURI, "api/user") {
remote, _ = url.Parse("http://" + this.user.host + ":" + this.user.port)
} else {
fmt.Fprintf(w, "404 Not Found")
return
}
proxy := httputil.NewSingleHostReverseProxy(remote)
proxy.ServeHTTP(w, r)}func startServer() {
// 注册被代理的服务器 (host， port)
service := &Service{
auth: &handle{host: "127.0.0.1", port: "8081"},
user: &handle{host: "127.0.0.1", port: "8082"},
}
err := http.ListenAndServe(":8888", service)
if err != nil {
log.Fatalln("ListenAndServe: ", err)
}}func main() {
startServer()}以上是Golang如何實現簡單的API網關的詳細內容。更多資訊請關注PHP中文網其他相關文章！
