PROSAGA码农传奇-go-当不提供http时，golang客户端负载均衡器

<div class =“post-text”itemprop =“text”>
  <P>
    加权随机选择有一个非常简单的算法：
  </p>
   <pre>
    <code>
      package main

import (
    "fmt"
    "math/rand"
)

type Endpoint struct {
    URL    string
    Weight int
}

func RandomWeightedSelector(endpoints []Endpoint) Endpoint {
    // this first loop should be optimised so it only gets computed once
    max := 0
    for _, endpoint := range endpoints {
        max = max + endpoint.Weight
    }

r := rand.Intn(max)
    for _, endpoint := range endpoints {
        if r < endpoint.Weight {
            return endpoint
        } else {
            r = r - endpoint.Weight
        }
    }
    // should never get to this point because r is smaller than max
    return Endpoint{}
}

func main() {
    endpoints := []Endpoint{
        {Weight: 1, URL: "https://web1.example.com"},
        {Weight: 2, URL: "https://web2.example.com"},
    }

count1 := 0
    count2 := 0

for i := 0; i < 100; i++ {
        switch RandomWeightedSelector(endpoints).URL {
        case "https://web1.example.com":
            count1++
        case "https://web2.example.com":
            count2++
        }
    }
    fmt.Println("Times web1: ", count1)
    fmt.Println("Times web2: ", count2)
}

</code>
  </pre>
  <P>
    在可以优化的情况下，这是最天真的。绝对是生产你不应该每次都计算最大值，但除此之外，这基本上是解决方案。
  </p>
  <P>
    这里有一个更专业和OO版本，每次都不会重新计算max：
  </p>
   <pre>
    <code>
      package main

import (
    "fmt"
    "math/rand"
)

type Endpoint struct {
    URL    string
    Weight int
}

type RandomWeightedSelector struct {
    max       int
    endpoints []Endpoint
}

func (rws *RandomWeightedSelector) AddEndpoint(endpoint Endpoint) {
    rws.endpoints = append(rws.endpoints, endpoint)
    rws.max += endpoint.Weight
}

func (rws *RandomWeightedSelector) Select() Endpoint {
    r := rand.Intn(rws.max)
    for _, endpoint := range rws.endpoints {
        if r < endpoint.Weight {
            return endpoint
        } else {
            r = r - endpoint.Weight
        }
    }
    // should never get to this point because r is smaller than max
    return Endpoint{}
}

func main() {
    var rws RandomWeightedSelector
    rws.AddEndpoint(Endpoint{Weight: 1, URL: "https://web1.example.com"})
    rws.AddEndpoint(Endpoint{Weight: 2, URL: "https://web2.example.com"})

count1 := 0
    count2 := 0

for i := 0; i < 100; i++ {
        switch rws.Select().URL {
        case "https://web1.example.com":
            count1++
        case "https://web2.example.com":
            count2++
        }
    }
    fmt.Println("Times web1: ", count1)
    fmt.Println("Times web2: ", count2)
}

</code>
  </pre>
  <P>
    对于基于端点等待时间等度量更新权重的部分，我将创建一个不同的对象，使用此度量来更新RandomWeightedSelector对象中的权重。我认为一起实施它将违背单一责任。
  </p>
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