dnschecker

dnschecker.go

package main

import (
	"context"
	"flag"
	"log"
	"net"
	"syscall"
	"time"

	"do/doge/context/sigctx"
)

func main() {
	name := flag.String("name", "kube-dns.kube-system.svc", "a DNS name to resolve")
	interval := flag.Duration("frequency", time.Second, "the frequency for each worker")
	flag.Parse()

	log.Println("resolving", *name)

	t := time.Tick(5 * *interval)
	ctx := sigctx.WithSignal(context.Background(), syscall.SIGTERM)

	for i := 0; i < 10; i++ {
		go func() {
			t := time.Tick(*interval)
			for {
				<-t
				resolve(*name, false)
			}
		}()
	}

	for {
		select {
		case <-ctx.Done():
			log.Println("done")
			return
		case <-t:
			resolve(*name, true)
		}
	}
}

func resolve(name string, output bool) {
	ctx, cancel := context.WithTimeout(context.Background(), time.Second*3)
	defer cancel()

	r := net.Resolver{}
	addrs, err := r.LookupHost(ctx, name)
	if err != nil {
		log.Println(err)
	}

	if output {
		log.Println("addrs =", addrs)
	}
}