Golang加权轮询负载均衡的实现

实现加权轮询负载均衡思路

代码实现一个加权负载均衡

• Weight            初始化时对节点约定的权重
• currentWeight     节点临时权重，每轮都会变化
• effectiveWeight   节点有效权重，默认与Weight相同
• totalWeight       所有节点有效权重之和：sum(effectiveWeight)

代码实现一个加权负载均衡

• currentWeight = currentWeight+effecitveWeight
• 选中最大的 currentWeight 节点为选中节点
• currentWeight = currentWeight-totalWeight  (4+3+2=9)

所以我们能够 在表格模拟运行情况：

加权轮询负载均衡代码

package load_balance

import (
 "errors"
 "strconv"

)

type WeightRoundRobinBalance struct {
 curIndex int
 rss      []*WeightNode
 rsw      []int

 //观察主体
 conf LoadBalanceConf
}

// 配置主题
type LoadBalanceConf interface {
 GetConf() []string
 WatchConf()
 UpdateConf(conf []string)
}

type WeightNode struct {
 addr            string // 服务器地址
 weight          int //权重值
 currentWeight   int //节点当前权重
 effectiveWeight int //有效权重
}

func (r *WeightRoundRobinBalance) Add(params ...string) error {
 if len(params) != 2 {
  return errors.New("param len need 2")
 }
 parInt, err := strconv.ParseInt(params[1], 10, 64)
 if err != nil {
  return err
 }
 node := &WeightNode{addr: params[0], weight: int(parInt)}
 node.effectiveWeight = node.weight
 r.rss = append(r.rss, node)
 return nil
}

func (r *WeightRoundRobinBalance) Next() string {
 total := 0
 var best *WeightNode
 for i := 0; i < len(r.rss); i++ {
  w := r.rss[i]
  //step 1 统计所有有效权重之和
  total += w.effectiveWeight

  //step 2 变更节点临时权重为的节点临时权重+节点有效权重
  w.currentWeight += w.effectiveWeight

  //step 3 有效权重默认与权重相同，通讯异常时-1, 通讯成功+1，直到恢复到weight大小
  if w.effectiveWeight < w.weight {
   w.effectiveWeight++
  }
  //step 4 选择最大临时权重点节点
  if best == nil || w.currentWeight > best.currentWeight {
   best = w
  }
 }
 if best == nil {
  return ""
 }
 //step 5 变更临时权重为 临时权重-有效权重之和
 best.currentWeight -= total
 return best.addr
}

func (r *WeightRoundRobinBalance) Get(key string) (string, error) {
 return r.Next(), nil
}

func (r *WeightRoundRobinBalance) SetConf(conf LoadBalanceConf) {
 r.conf = conf
}

测试代码

package load_balance

import (
 "fmt"
 "testing"
)

func TestLB(t *testing.T) {
 rb := &WeightRoundRobinBalance{}
 rb.Add("127.0.0.1:2003", "4") //0
 // rb.Add("127.0.0.1:2004", "3") //1
 rb.Add("127.0.0.1:2005", "2") //2

 fmt.Println(rb.Next())
 fmt.Println(rb.Next())
 fmt.Println(rb.Next())
 fmt.Println(rb.Next())
 fmt.Println(rb.Next())
 fmt.Println(rb.Next())
 fmt.Println(rb.Next())
 fmt.Println(rb.Next())
 fmt.Println(rb.Next())
 fmt.Println(rb.Next())
 fmt.Println(rb.Next())
 fmt.Println(rb.Next())
 fmt.Println(rb.Next())
 fmt.Println(rb.Next())
}

测试结果

$ go test
127.0.0.1:2003
127.0.0.1:2005
127.0.0.1:2003
127.0.0.1:2003
127.0.0.1:2005
127.0.0.1:2003
127.0.0.1:2003
127.0.0.1:2005
127.0.0.1:2003
127.0.0.1:2003
127.0.0.1:2005
127.0.0.1:2003
127.0.0.1:2003
127.0.0.1:2005
PASS
ok      gateway/_test/demo      0.080s

## 127.0.0.1:2003 为 127.0.0.1:2005 权重两倍。而从答应结果上看，符合要求

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