1、真实服务器
package main
import (
"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:" + port
rs := &realServer{Addr: addr}
go rs.Run()
}
signal.Notify(doneCh,syscall.SIGINT,syscall.SIGTERM)
<- doneCh
}
2、反向代理代码框架
//
package httpServer
import (
"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.go
package main
import (
"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.go
type HttpServer struct {
Host string
Weight 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 []int
for 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 := 0
for i:=0;i<len(lb.Servers);i++{
weightSum += lb.Servers[i].Weight
}
// 随机数获取
randNum := rand.Intn(weightSum)
sum := 0
for 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index
if 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 *LoadBalance
func init(){
lb = NewLoadBalance()
}// httpserver.go
// 结构体中加上当前index值
type LoadBalance struct {
Index int
Servers []*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 main
import (
"log"
"net/http"
"net/http/httputil"
"net/url"
. "loadBalanceDemo/httpServer"
)
type ReveseProxyHandler struct {
}
var lb *LoadBalance
var indexArr []int
func 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URL
if 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 := 0
for i:=0;i<len(lb.Servers);i++{
sum += lb.Servers[i].Weight
if 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httpserver
func (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IP
url,err := url.Parse(lb.GetHttpServerByIpHash(r.RemoteAddr).Host)url_hash 算法
// url_hash
url,err := url.Parse(lb.GetHttpServerByUrlHash(r.RequestURI).Host)// url_hash
func (lb *LoadBalance) GetHttpServerByUrlHash(url string) *HttpServer{
index := int(crc32.ChecksumIEEE([]byte(url))) % len(lb.Servers)
return lb.Servers[index]
}有疑问加站长微信联系（非本文作者）
