Use workers instead spawning goroutines for each incoming DNS request

benchmark_test.go

@@ -0,0 +1,90 @@
+package dns
+
+import (
+	"fmt"
+	"net"
+	"sync"
+	"testing"
+	"time"
+)
+
+func BenchmarkServer(b *testing.B) {
+	HandleFunc(".", erraticHandler)
+	defer HandleRemove(".")
+	for _, i := range []int{0, 50, 100, 200, 1000} {
+		benchmark(i, b)
+	}
+}
+
+func benchmark(workers int, b *testing.B) {
+	s, addr, err := runLocalUDPServer(workers)
+	if err != nil {
+		b.Fatalf("unable to run test server: %v", err)
+	}
+	defer s.Shutdown()
+
+	m := new(Msg)
+	m.SetQuestion("domain.local.", TypeA)
+
+	test := fmt.Sprintf("%d_workers", workers)
+	b.Run(test, func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			_, err := Exchange(m, addr)
+			if err != nil {
+				b.Fatalf("Exchange() failed: %v", err)
+			}
+		}
+	})
+}
+
+var (
+	rrA, _    = NewRR(". IN 0 A 192.0.2.53")
+	rrAAAA, _ = NewRR(". IN 0 AAAA 2001:DB8::53")
+)
+
+func erraticHandler(w ResponseWriter, r *Msg) {
+	r.Response = true
+
+	switch r.Question[0].Qtype {
+	case TypeA:
+		rr := *(rrA.(*A))
+		rr.Header().Name = r.Question[0].Name
+		r.Answer = []RR{&rr}
+		r.Rcode = RcodeSuccess
+	case TypeAAAA:
+		rr := *(rrAAAA.(*AAAA))
+		rr.Header().Name = r.Question[0].Name
+		r.Answer = []RR{&rr}
+		r.Rcode = RcodeSuccess
+	default:
+		r.Rcode = RcodeServerFailure
+	}
+
+	w.WriteMsg(r)
+}
+
+func runLocalUDPServer(workers int) (*Server, string, error) {
+	pc, err := net.ListenPacket("udp", "127.0.0.1:0")
+	if err != nil {
+		return nil, "", err
+	}
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+	server := &Server{
+		PacketConn:        pc,
+		ReadTimeout:       time.Hour,
+		WriteTimeout:      time.Hour,
+		NotifyStartedFunc: wg.Done,
+		Handler:           DefaultServeMux,
+		Workers:           workers,
+	}
+
+	go func() {
+		server.ActivateAndServe()
+		pc.Close()
+	}()
+
+	wg.Wait()
+	return server, pc.LocalAddr().String(), nil
+}