Block serving requests until first full update

Given that this might lead to 404 responses eventhough the request is
valid, we should wait until the first full update cycle is done.

app.go

@@ -94,6 +94,9 @@ func (a *theApp) UpdateDomains(domains domains) {
 func (a *theApp) Run() {
 	var wg sync.WaitGroup
+	lastUpdate := []byte("first-update")
+	updateDomains(a.Domain, a.UpdateDomains, &lastUpdate)
+
 	// Listen for HTTP
 	for _, fd := range a.ListenHTTP {
 		wg.Add(1)
@@ -143,8 +146,7 @@ func (a *theApp) Run() {
 			}
 		}(a.ListenMetrics)
 	}
-
-	go watchDomains(a.Domain, a.UpdateDomains, time.Second)
+	go watchDomains(a.Domain, a.UpdateDomains, time.Second, &lastUpdate)
 	wg.Wait()
 }

domains.go

@@ -124,38 +124,39 @@ func (d domains) ReadGroups(rootDomain string) error {
 	return nil
 }
-func watchDomains(rootDomain string, updater domainsUpdater, interval time.Duration) {
-	lastUpdate := []byte("no-update")
-
+// We should block other goroutines until the first update has been completed
+func watchDomains(rootDomain string, updater domainsUpdater, interval time.Duration, lastUpdate *[]byte) {
 	for {
-		// Read the update file
-		update, err := ioutil.ReadFile(".update")
-		if err != nil && !os.IsNotExist(err) {
-			log.Println("Failed to read update timestamp:", err)
-		}
-		// If it's the same ignore
-		if bytes.Equal(lastUpdate, update) {
-			time.Sleep(interval)
-			continue
-		}
-		lastUpdate = update
-		started := time.Now()
-		domains := make(domains)
-		domains.ReadGroups(rootDomain)
-		duration := time.Since(started)
-		log.Println("Updated", len(domains), "domains in", duration, "Hash:", update)
-		if updater != nil {
-			updater(domains)
-		}
-		// Update prometheus metrics
-		metrics.DomainLastUpdateTime.Set(float64(time.Now().UTC().Unix()))
-		metrics.DomainsServed.Set(float64(len(domains)))
-		metrics.DomainUpdates.Inc()
-		time.Sleep(interval)
+		time.Sleep(interval)
+		updateDomains(rootDomain, updater, lastUpdate)
+	}
+}
+func updateDomains(rootDomain string, updater domainsUpdater, lastUpdate *[]byte) {
+	// Read the update file
+	update, err := ioutil.ReadFile(".update")
+	if err != nil && !os.IsNotExist(err) {
+		log.Println("Failed to read update timestamp:", err)
+	}
+	if bytes.Equal(*lastUpdate, update) {
+		return
+	}
+	*lastUpdate = update
+	started := time.Now()
+	domains := make(domains)
+	domains.ReadGroups(rootDomain)
+	duration := time.Since(started)
+	log.Println("Updated", len(domains), "domains in", duration, "Hash:", update)
+	if updater != nil {
+		updater(domains)
 	}
+
+	// Update prometheus metrics
+	metrics.DomainLastUpdateTime.Set(float64(time.Now().UTC().Unix()))
+	metrics.DomainsServed.Set(float64(len(domains)))
+	metrics.DomainUpdates.Inc()
 }

domains_test.go

@@ -52,9 +52,10 @@ func TestWatchDomains(t *testing.T) {
 	setUpTests()
 	update := make(chan domains)
+	lastUpdate := []byte("no-update")
 	go watchDomains("gitlab.io", func(domains domains) {
 		update <- domains
-	}, time.Microsecond*50)
+	}, time.Microsecond*50, &lastUpdate)
 	defer os.Remove(updateFile)

helpers_test.go

@@ -47,6 +47,7 @@ var InsecureHTTPSClient = &http.Client{
 	Transport: &http.Transport{
 		TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
 	},
+	Timeout: 10 * time.Second,
 }
 var CertificateFixture = `-----BEGIN CERTIFICATE-----
@@ -153,11 +154,9 @@ func RunPagesProcess(t *testing.T, pagesPath string, listeners []ListenSpec, pro
 	// for now. Without it, intermittent failures occur.
 	//
 	// TODO: replace this with explicit status from the pages binary
-	// TODO: fix the first-request race
 	for _, spec := range listeners {
 		spec.WaitUntilListening()
 	}
-	time.Sleep(500 * time.Millisecond)
 	return func() {
 		cmd.Process.Signal(os.Interrupt)