example.go

package main

import (
	"errors"
	"log"

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

func main() {
	log.SetFlags(0)

	const (
		commandName   = "my-endpoint"
		errorPercent  = 5
		maxConcurrent = 1000
	)
	hystrix.ConfigureCommand(commandName, hystrix.CommandConfig{
		ErrorPercentThreshold: errorPercent,
		MaxConcurrentRequests: maxConcurrent,
	})
	var (
		primeWith  = hystrix.DefaultVolumeThreshold * 2
		shouldPass = func(n int) bool { return (float64(n) / float64(primeWith+n)) <= (float64(errorPercent-1) / 100.0) }
	)

	var myErr error
	run := func() error { return myErr }
	log.Printf("priming with %d successful requests", primeWith)

	for i := 0; i < primeWith; i++ {
		if err := hystrix.Do(commandName, run, nil); err != myErr {
			log.Fatalf("initial request %d failed: %v", i+1, err)
		}
	}

	log.Printf("switching to errors...")
	myErr = errors.New("kaboom")
	log.Printf("now the next few requests should give us our error: %v", myErr)

	for i := 0; shouldPass(i); i++ {
		if err := hystrix.Do(commandName, run, nil); err != myErr {
			log.Fatalf("post-error request %d failed: %v", i+1, err)
		}
		log.Printf("got expected error %d", i+1)
	}

	log.Printf("the circuit should have opened by now")

	for i := 0; i < 5; i++ {
		if err := hystrix.Do(commandName, run, nil); err != hystrix.ErrCircuitOpen {
			log.Fatalf("got unexpected error at request %d: %v", i+1, err)
		}
		log.Printf("got expected error: %v", hystrix.ErrCircuitOpen)
	}

	log.Printf("everything works as expected")
}