cmd/cli: refactoring self-check process

Make the code cleaner and easier to maintain.

cmd/cli/cli.go

@@ -1647,11 +1647,6 @@ func selfCheckStatus(s service.Service) (bool, service.Status, error) {
 
 	mainLog.Load().Debug().Msg("ctrld listener is ready")
 	mainLog.Load().Debug().Msg("performing self-check")
-	bo := backoff.NewBackoff("self-check", logf, 10*time.Second)
-	bo.LogLongerThan = 500 * time.Millisecond
-	ctx := context.Background()
-	maxAttempts := 20
-	c := new(dns.Client)
 	var (
 		lcChanged map[string]*ctrld.ListenerConfig
 		ucChanged map[string]*ctrld.UpstreamConfig
@@ -1669,12 +1664,6 @@ func selfCheckStatus(s service.Service) (bool, service.Status, error) {
 		// Nothing to do, return the status as-is.
 		return true, status, nil
 	}
-	watcher, err := fsnotify.NewWatcher()
-	if err != nil {
-		mainLog.Load().Error().Err(err).Msg("could not watch config change")
-		return false, status, err
-	}
-	defer watcher.Close()
 
 	v.OnConfigChange(func(in fsnotify.Event) {
 		mu.Lock()
@@ -1683,52 +1672,56 @@ func selfCheckStatus(s service.Service) (bool, service.Status, error) {
 			mainLog.Load().Error().Msgf("failed to unmarshal listener config: %v", err)
 			return
 		}
+		cfg.Listener = lcChanged
 		if err := v.UnmarshalKey("upstream", &ucChanged); err != nil {
 			mainLog.Load().Error().Msgf("failed to unmarshal upstream config: %v", err)
 			return
 		}
+		cfg.Upstream = ucChanged
 	})
 	v.WatchConfig()
+
+	lc := cfg.FirstListener()
+	addr := net.JoinHostPort(lc.IP, strconv.Itoa(lc.Port))
+	getInternalDomainFn := func() string { return selfCheckInternalTestDomain }
+	getExternalDomainFn := func() string { return cfg.FirstUpstream().VerifyDomain() }
+	if err := selfCheckResolveDomain(context.TODO(), addr, "internal", getInternalDomainFn); err != nil {
+		return false, status, err
+	}
+	if err := selfCheckResolveDomain(context.TODO(), addr, "external", getExternalDomainFn); err != nil {
+		return false, status, err
+	}
+	return true, status, nil
+}
+
+// selfCheckResolveDomain performs DNS test query against ctrld listener.
+func selfCheckResolveDomain(ctx context.Context, addr, scope string, getDomainFn func() string) error {
+	bo := backoff.NewBackoff("self-check", logf, 10*time.Second)
+	bo.LogLongerThan = 500 * time.Millisecond
+	maxAttempts := 20
+	c := new(dns.Client)
+
 	var (
-		lastAnswer     *dns.Msg
+		lastAnswer *dns.Msg
-		lastErr        error
+		lastErr    error
-		internalTested bool
 	)
+	domain := ""
 	for i := 0; i < maxAttempts; i++ {
-		mu.Lock()
+		domain = getDomainFn()
-		if lcChanged != nil {
-			cfg.Listener = lcChanged
-		}
-		if ucChanged != nil {
-			cfg.Upstream = ucChanged
-		}
-		mu.Unlock()
-		lc := cfg.FirstListener()
-		domain = cfg.FirstUpstream().VerifyDomain()
-		if !internalTested {
-			domain = selfCheckInternalTestDomain
-		}
 		if domain == "" {
 			continue
 		}
-
 		m := new(dns.Msg)
 		m.SetQuestion(domain+".", dns.TypeA)
 		m.RecursionDesired = true
-		r, _, exErr := exchangeContextWithTimeout(c, time.Second, m, net.JoinHostPort(lc.IP, strconv.Itoa(lc.Port)))
+		r, _, exErr := exchangeContextWithTimeout(c, time.Second, m, addr)
 		if r != nil && r.Rcode == dns.RcodeSuccess && len(r.Answer) > 0 {
-			internalTested = domain == selfCheckInternalTestDomain
+			mainLog.Load().Debug().Msgf("%s self-check against %q succeeded", scope, domain)
-			if internalTested {
+			return nil
-				mainLog.Load().Debug().Msgf("internal self-check against %q succeeded", domain)
-				continue // internal domain test ok, continue with external test.
-			} else {
-				mainLog.Load().Debug().Msgf("external self-check against %q succeeded", domain)
-			}
-			return true, status, nil
 		}
 		// Return early if this is a connection refused.
 		if errConnectionRefused(exErr) {
-			return false, status, exErr
+			return exErr
 		}
 		lastAnswer = r
 		lastErr = exErr
@@ -1741,8 +1734,6 @@ func selfCheckStatus(s service.Service) (bool, service.Status, error) {
 			mainLog.Load().Err(err).Msgf("failed to connect to upstream.%s, endpoint: %s", name, uc.Endpoint)
 		}
 	}
-	lc := cfg.FirstListener()
-	addr := net.JoinHostPort(lc.IP, strconv.Itoa(lc.Port))
 	marker := strings.Repeat("=", 32)
 	mainLog.Load().Debug().Msg(marker)
 	mainLog.Load().Debug().Msgf("listener address       : %s", addr)
@@ -1753,9 +1744,8 @@ func selfCheckStatus(s service.Service) (bool, service.Status, error) {
 		for _, s := range strings.Split(lastAnswer.String(), "\n") {
 			mainLog.Load().Debug().Msgf("%s", s)
 		}
-		return false, status, errSelfCheckNoAnswer
 	}
-	return false, status, lastErr
+	return errSelfCheckNoAnswer
 }
 
 func userHomeDir() (string, error) {