hystrix.go

package main

import (
	"errors"
	"log"
	"net/http"
	_ "net/http/pprof"
	"time"

	"github.com/afex/hystrix-go/hystrix"
)

const (
	hystrixCmd = "sample_command"
)

func main() {
	hystrix.ConfigureCommand(hystrixCmd, hystrix.CommandConfig{
		Timeout:               1000,
		MaxConcurrentRequests: 5,
		SleepWindow:           1000,
		ErrorPercentThreshold: 1,
	})

	http.HandleFunc("/fn", handlerFn)
	_ = http.ListenAndServe(":8080", nil)
}

var counter int

func handlerFn(w http.ResponseWriter, r *http.Request) {
	resultCh := make(chan []byte)
	errCh := hystrix.Go(hystrixCmd, func() error {
		counter++
		if counter < 10 {
			return errors.New("forced failure")
		}

		time.Sleep(time.Hour)
		resultCh <- []byte("success")
		return nil
	}, nil)

	select {
	case <-resultCh:
		log.Println("Success")
		w.WriteHeader(http.StatusOK)
	case err := <-errCh:
		log.Println("Err:", err, counter)
		w.WriteHeader(http.StatusServiceUnavailable)
	}
}

run.sh

for i in `seq 1 2`; do for i in `seq 1 10`; do curl http://localhost:8080/fn &; done; sleep 11; done;
for i in `seq 1 100`; do for i in `seq 1 10`; do curl http://localhost:8080/fn &; done; sleep 2; done;