22. The fuse learn to control the maximum number of concurrent

Fuse control maximum number of concurrent

package main

import (
    "fmt"
    "github.com/afex/hystrix-go/hystrix"
    "math/rand"
    "sync"
    "time"
)

type Product struct {
    ID    int
    Title string
    Price int
}

func getProduct() (Product, error) {
    r := rand.Intn(10)
    if r < 6 { //模拟api卡顿和超时效果
        //time.Sleep(time.Second * 4)
    }
    return Product{
        ID:    101,
        Title: "Golang从入门到精通",
        Price: 12,
    }, nil
}

func RecProduct() (Product, error) {
    return Product{
        ID:    999,
        Title: "推荐商品",
        Price: 120,
    }, nil

}

func main() {
    rand.Seed(time.Now().UnixNano())
    configA := hystrix.CommandConfig{ //创建一个hystrix的config
        Timeout:               3000, //command运行超过3秒就会报超时错误
        MaxConcurrentRequests: 5,    //控制最大并发数为5，如果超过5会调用我们传入的回调函数降级
    }
    hystrix.ConfigureCommand("get_prod", configA) //hystrix绑定command
    resultChan := make(chan Product, 1)

    wg := &sync.WaitGroup{}

    for i := 0; i < 10; i++ {
        go (func() {
            wg.Add(1)
            defer wg.Done()
            errs := hystrix.Go("get_prod", func() error { //使用hystrix来讲我们的操作封装成command,hystrix返回值是一个chan error
                p, _ := getProduct() //这里会随机延迟0-4秒
                resultChan <- p
                return nil //这里返回的error在回调中可以获取到，也就是下面的e变量
            }, func(e error) error {
                rcp, err := RecProduct() //推荐商品,如果这里的err不是nil,那么就会忘errs中写入这个err，下面的select就可以监控到
                resultChan <- rcp
                return err
            })
            select {
            case getProd := <-resultChan:
                fmt.Println(getProd)
            case err := <-errs: //使用hystrix.Go时返回值是chan error各个协程的错误都放到errs中
                fmt.Println(err, 1)
            }
        })()
    }
    wg.Wait()
}

Is known from notes (Wiz)