simple go app to check the health of a url then do stuff if unhealthy

health-checker.go

package main

import (
	"flag"
	"fmt"
	"log"
	"net/http"
	"os"
	"time"
)

const (
	checkInterval = time.Second * 30
	maxSleep = time.Minute * 5
)

func main() {
	fs := flag.NewFlagSet("sidekick-flagset", flag.ExitOnError)
	healthURL := fs.String("health-url", "", "health url to check")
	etcdURL := fs.String("etcd-url", "http://localhost:4001", "etcd api endpoint")

	if err := fs.Parse(os.Args[1:]); err != nil {
		fmt.Fprintln(os.Stderr, err.Error())
		os.Exit(1)
	}

	if *healthURL == "" {
		fmt.Fprintln(os.Stderr, "health-url is required")
		os.Exit(1)
	}

	fmt.Printf("started using: etcd-url=%s, health-url=%s\n", *etcdURL, *healthURL)

	var sleep time.Duration
	for {
		if HealthCheck(*healthURL) {
			sleep = checkInterval
			fmt.Printf("healthy, retrying in: %v\n", sleep)
		} else {
			sleep = ExpBackoff(sleep, maxSleep)
			log.Printf("Unhealthy, retrying in: %v\n", sleep)
			DoStuff()
		}
		time.Sleep(sleep)
	}
}

func DoStuff() {
	fmt.Println("stuff")
}

func HealthCheck(url string) bool {
	resp, err := http.Get(url)
	if err != nil {
		log.Printf("Error during health check: %v", err)
		return false
	}

	if resp.StatusCode == http.StatusOK {
		return true
	}

	return false
}

func ExpBackoff(prev, max time.Duration) time.Duration {
	if prev == 0 {
		return time.Second
	}
	if prev > max/2 {
		return max
	}
	return 2 * prev
}