爱站程序员基地1、真实服务器
package mainimport (\"fmt\"\"log\"\"net/http\"\"os\"\"os/signal\"\"strconv\"\"syscall\"\"time\")type realServer struct {Addr string}func (rs *realServer) HelloHandler(w http.ResponseWriter,r *http.Request){data := fmt.Sprintf(\"[%s] http://%s%s \\n\\n\",rs.Addr,rs.Addr,r.RequestURI)w.Write([]byte(data))}func (rs *realServer) Run(){fmt.Println(\"Http server tart to serve at :\",rs.Addr)mux := http.NewServeMux()mux.HandleFunc(\"/\",rs.HelloHandler)server := &http.Server{Addr: rs.Addr,Handler: mux,WriteTimeout: time.Second * 3,}go func(){if err := server.ListenAndServe();err != nil{log.Fatal(\"Start http server failed,err:\",err)}}()}func main() {doneCh := make(chan os.Signal)for i:=0;i<5;i++{port := \"808\" + strconv.Itoa(i)addr := \"127.0.0.1:\" + portrs := &realServer{Addr: addr}go rs.Run()}signal.Notify(doneCh,syscall.SIGINT,syscall.SIGTERM)<- doneCh}
2、反向代理代码框架
//package httpServerimport (\"math/rand\"\"time\")type HttpServer struct {Host string}type LoadBalance struct {Servers []*HttpServer}func NewLoadBalance()*LoadBalance{return &LoadBalance{Servers:make([]*HttpServer,0)}}func NewHttpServer(host string)*HttpServer{return &HttpServer{Host:host,}}func (lb *LoadBalance)Add(server *HttpServer){lb.Servers = append(lb.Servers,server)}
启动服务
// server.gopackage mainimport (\"log\"\"net/http\"\"net/http/httputil\"\"net/url\". \"gostudy/reverseProxyDemo/httpServer\")type ReveseProxyHandler struct {}func (rph *ReveseProxyHandler)ServeHTTP(w http.ResponseWriter,r *http.Request){lb := NewLoadBalance()lb.Add(NewHttpServer(\"http://127.0.0.1:8080\"))lb.Add(NewHttpServer(\"http://127.0.0.1:8081\"))lb.Add(NewHttpServer(\"http://127.0.0.1:8082\"))lb.Add(NewHttpServer(\"http://127.0.0.1:8083\"))lb.Add(NewHttpServer(\"http://127.0.0.1:8084\"))url,err := url.Parse(lb.GetHttpServerByRandom().Host)if err != nil {log.Println(\"[ERR] url.Parse failed,err:\",err)return}proxy := httputil.NewSingleHostReverseProxy(url)proxy.ServeHTTP(w,r)}func main() {proxy := &ReveseProxyHandler{}log.Println(\"Start to serve at 127.0.0.1:8888\")if err := http.ListenAndServe(\":8888\",proxy);err !=nil{log.Fatal(\"Failed to start reverse proxy server ,err:\",err)}}
3、随机负载均衡算法
// httpServer/reverseProxy.go// 随机负载均衡func (lb *LoadBalance)GetHttpServerByRandom()*HttpServer{rand.Seed(time.Now().UnixNano())index := rand.Intn(len(lb.Servers))return lb.Servers[index]}
测试结果
$ for i in {0..9};do curl -s http://127.0.0.1:8888/reverseproxydemo?id=123;done[127.0.0.1:8083] http://127.0.0.1:8083/reverseproxydemo?id=123[127.0.0.1:8084] http://127.0.0.1:8084/reverseproxydemo?id=123[127.0.0.1:8082] http://127.0.0.1:8082/reverseproxydemo?id=123[127.0.0.1:8080] http://127.0.0.1:8080/reverseproxydemo?id=123[127.0.0.1:8081] http://127.0.0.1:8081/reverseproxydemo?id=123[127.0.0.1:8082] http://127.0.0.1:8082/reverseproxydemo?id=123[127.0.0.1:8080] http://127.0.0.1:8080/reverseproxydemo?id=123[127.0.0.1:8081] http://127.0.0.1:8081/reverseproxydemo?id=123[127.0.0.1:8080] http://127.0.0.1:8080/reverseproxydemo?id=123[127.0.0.1:8084] http://127.0.0.1:8084/reverseproxydemo?id=123
加权随机
原理：获取到所有节点的权重值，将weight个当前节点Index加到一个[]int，并随机从中获取一个index，例如：
A ： B ： C = 5:2:1 且ABC三个节点的Index分别为0,1,2，那么新建一个如下是切片：
[]int{0,0,0,0,0,1,1,2} ，然后通过rand(len([]int)) 随机拿到一个index
// httpserver.gotype HttpServer struct {Host stringWeight int}func NewHttpServer(host string,weight int)*HttpServer{return &HttpServer{Host:host,Weight:weight,}}// 加权随机func (lb *LoadBalance)GetHttpServerByRandomWithWeight(httpServerArr []int)*HttpServer{rand.Seed(time.Now().UnixNano())index := rand.Intn(len(httpServerArr))return lb.Servers[httpServerArr[index]]}
// loadBalanceDemo/loadbalance.go// 加权随机var httpServerArr []intfor index,server := range lb.Servers{if server.Weight > 0 {for i:=0;i<server.Weight;i++{httpServerArr = append(httpServerArr,index)}}}url,err := url.Parse(lb.GetHttpServerByRandomWithWeight(httpServerArr).Host)
加权随机算法优化版
上面的加权随机算法实现起来比较简单，但存在一个明显弊端，如果weight值的大小将直接影响切片大小，例如5:2 跟 50000:20000 本质上是一样的，但后者将占用更多的内存空间。因此我们需要对该算法做下优化，将N个节点权重计算出N个区间，然后取随机数rand(weightSum)，看该数落在哪个区间就返回该区间对应的index值，举个例子：
假设A:B:C = 5:2:1
那么我们先计算出3个区间：5,7(5+2),8(5+2+1)
[0,5) [5,7) [7,8)
然后取rand(5+2+1)，假设获取到的值为6，则落在[5,7) 这个区间，返回index=1
可以看出rand(7)随机数落在各个区间分布如下：
[0,5) ： 0,1,2,3,4
[5,7) ：5,6
[7,8) ：7
正好是5:2:1
下面是具体实现：
// 加权随机优化版func (lb *LoadBalance)GetHttpServerByRandomWithWeight2()*HttpServer{rand.Seed(time.Now().UnixNano())// 计算所有节点权重值之和weightSum := 0for i:=0;i<len(lb.Servers);i++{weightSum += lb.Servers[i].Weight}// 随机数获取randNum := rand.Intn(weightSum)sum := 0for i := 0;i<len(lb.Servers);i++{sum += lb.Servers[i].Weight// 因为区间是[ ) ，左闭右开，故随机数小于当前权重sum值，则代表落在该区间，返回当前的indexif randNum < sum {return lb.Servers[i]}}return lb.Servers[0]}
轮询算法
假设有ABC 3台机器，那么请求过来将按照ABCABC 这样的顺顺序将请求反向代理到后端服务器
原理是记录当前的index值，每次请求+1 取模（这里仅演示算法，未考虑线程安全问题，没有加锁）
// loadbalance.go// 由于每次请求需要保存当前的index值，所以使用全局变量lb，并在初始化函数中初始化lb实例var lb *LoadBalancefunc init(){lb = NewLoadBalance()}
// httpserver.go// 结构体中加上当前index值type LoadBalance struct {Index intServers []*HttpServer}// 轮询func (lb *LoadBalance)GetHttpServerByRoundRobin() *HttpServer{server := lb.Servers[lb.Index]lb.Index = (lb.Index + 1)% len(lb.Servers)return server}
加权轮询算法-切片算法
/ 加权轮询func (lb *LoadBalance)GetHttpServerByRoundRobinWithWeight(indexArr []int) *HttpServer{lb.Index = (lb.Index + 1)% len(indexArr)fmt.Println(indexArr)return lb.Servers[indexArr[lb.Index]]}
package mainimport (\"log\"\"net/http\"\"net/http/httputil\"\"net/url\". \"loadBalanceDemo/httpServer\")type ReveseProxyHandler struct {}var lb *LoadBalancevar indexArr []intfunc init(){lb = NewLoadBalance()lb.Add(NewHttpServer(\"http://127.0.0.1:8082\",5))lb.Add(NewHttpServer(\"http://127.0.0.1:8083\",2))lb.Add(NewHttpServer(\"http://127.0.0.1:8084\",1))// 加权轮询indexArr = make([]int,0)for index,server := range lb.Servers{if server.Weight > 0{for i:=0;i<server.Weight;i++{indexArr = append(indexArr,index)}}}}func (rph *ReveseProxyHandler)ServeHTTP(w http.ResponseWriter,r *http.Request){// 浏览器访问时默认会请求/favicon.ico，这里忽略该URLif r.URL.Path == \"/favicon.ico\"{return}url,err := url.Parse(lb.GetHttpServerByRoundRobinWithWeight(indexArr).Host)if err != nil {log.Println(\"[ERR] url.Parse failed,err:\",err)return}proxy := httputil.NewSingleHostReverseProxy(url)proxy.ServeHTTP(w,r)}func main() {proxy := &ReveseProxyHandler{}log.Println(\"Start to serve at 127.0.0.1:8888\")if err := http.ListenAndServe(\":8888\",proxy);err !=nil{log.Fatal(\"Failed to start reverse proxy server ,err:\",err)}}
加权轮询算法-区间算法
// 加权轮询区间算法func (lb *LoadBalance)GetHttpServerByRoundRobinWithWeight2()*HttpServer{server := lb.Servers[0]sum := 0for i:=0;i<len(lb.Servers);i++{sum += lb.Servers[i].Weightif lb.Index < sum{server = lb.Servers[i]if lb.Index == sum -1 && i != len(lb.Servers)-1{lb.Index++}else{lb.Index = (lb.Index+1) % sum}fmt.Println(lb.Index)break}}return server}
ip_hash 算法
// ip_hash// 对客户端IP 做hash 取模得到有一个固定的index，返回固定的httpserverfunc (lb *LoadBalance)GetHttpServerByIpHash(ip string) *HttpServer{index := int(crc32.ChecksumIEEE([]byte(ip))) % len(lb.Servers)return lb.Servers[index]}
// server.go// ip_hash// 传入客户端IPurl,err := url.Parse(lb.GetHttpServerByIpHash(r.RemoteAddr).Host)
url_hash 算法
// url_hashurl,err := url.Parse(lb.GetHttpServerByUrlHash(r.RequestURI).Host)
// url_hashfunc (lb *LoadBalance) GetHttpServerByUrlHash(url string) *HttpServer{index := int(crc32.ChecksumIEEE([]byte(url))) % len(lb.Servers)return lb.Servers[index]}
