hystrix-demo/demo.go

package main

import (
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"strings"
	"time"

	h "github.com/afex/hystrix-go/hystrix"
	y "gopkg.in/yaml.v3"
)

var cmds = map[string]h.CommandConfig{
	"defaults": {
		Timeout:                h.DefaultTimeout,
		MaxConcurrentRequests:  h.DefaultMaxConcurrent,
		RequestVolumeThreshold: h.DefaultVolumeThreshold,
		SleepWindow:            h.DefaultSleepWindow,
		ErrorPercentThreshold:  h.DefaultErrorPercentThreshold,
	},
	"robots": {
		Timeout:                100,
		MaxConcurrentRequests:  1,
		RequestVolumeThreshold: 1,
		SleepWindow:            3000,
		ErrorPercentThreshold:  1,
	},
}

func robots() error {
	res, err := http.Get("https://osinet.fr/robots.txt")
	if err != nil {
		return err
	}
	if res.StatusCode >= http.StatusBadRequest {
		return fmt.Errorf("HTTP Error response: %s", res.Status)
	}
	b, err := io.ReadAll(res.Body)
	if err != nil {
		return err
	}
	fmt.Printf("%s\n", strings.Replace(string(b[0:20]), "\n", "\t", -1))
	return nil
}

func robotsFB(e error) error {
	ce, ok := e.(h.CircuitError)
	if !ok {
		return fmt.Errorf("unexpected error: %w", e)
	}
	switch ce.Message {
	case "circuit open":
		fmt.Println("FB Short-circuit")
	case "timeout":
		fmt.Println("FB Timeout response")
	default:
		log.Println("FB", e.Error())
	}
	return nil
}

func showCircuitSettings() {
	e := y.NewEncoder(os.Stdout)
	defer e.Close()
	e.SetIndent(2)
	fmt.Println(e.Encode(h.GetCircuitSettings()))
}

func showCircuit(name string) {
	r, created, err := h.GetCircuit(name)
	fmt.Printf("Name: %s, Created it: %t, error: %v\n", r.Name, created, err)
	if err == nil {
		fmt.Printf("IsOpen: %t, AllowRequest: %t", r.IsOpen(), r.AllowRequest())
	}
}

func streamStats() {
	sh := h.NewStreamHandler()
	sh.Start()

	http.Handle("/", sh)

	err := http.ListenAndServe(":4000", nil)
	fmt.Printf("L&S: %#v\n", err)
	sh.Stop()
}

func main() {
	h.SetLogger(log.Default())
	h.Configure(cmds)
	// showCircuit("robots")
	// show(h.GetCircuitSettings())
	go streamStats()

	for i := 0; i < 30; i++ {
		t0 := time.Now()
		err := h.Do("robots", robots, robotsFB)
		d := time.Since(t0)
		if err != nil {
			fmt.Printf("%2d in %v Error: %v\n", i, d, err)
		} else {
			fmt.Printf("%2d in %v OK\n", i, d)
		}
		time.Sleep(1000 * time.Millisecond)
		// if i%10 == 0 {
		// 	h.Flush()
		// }
	}
}