fix: handle unresolved dev DNS updater hostnames

Signed-off-by: immanuwell <pchpr.00@list.ru>

Author: immanuwell

src/utils/dev_dns_updater/BUILD.bazel

@@ -15,7 +15,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 load("@io_bazel_rules_go//go:def.bzl", "go_library")
-load("//bazel:pl_build_system.bzl", "pl_go_binary")
+load("//bazel:pl_build_system.bzl", "pl_go_binary", "pl_go_test")
 
 go_library(
     name = "dev_dns_updater_lib",
@@ -44,3 +44,14 @@ pl_go_binary(
     embed = [":dev_dns_updater_lib"],
     visibility = ["//src:__subpackages__"],
 )
+
+pl_go_test(
+    name = "dev_dns_updater_test",
+    srcs = ["dev_dns_updater_test.go"],
+    embed = [":dev_dns_updater_lib"],
+    deps = [
+        "@io_k8s_api//core/v1:core",
+        "@io_k8s_apimachinery//pkg/apis/meta/v1:meta",
+        "@io_k8s_apimachinery//pkg/watch",
+    ],
+)

src/utils/dev_dns_updater/dev_dns_updater.go

@@ -50,6 +50,7 @@ var dnsEntriesByServiceCfg = map[string][]string{
 }
 
 var dnsEntriesByService = map[string][]string{}
+var lookupIP = net.LookupIP
 
 type svcInfo struct {
 	SvcName string
@@ -59,7 +60,7 @@ type svcInfo struct {
 func init() {
 	pflag.String("n", "plc-dev", "The namespace to watch (plc-dev) by default")
 	pflag.String("domain-name", "dev.withpixie.dev", "The domain name to use")
-	pflag.String("kubeconfig", filepath.Join(homeDir(), ".kube", "config"), "(optional) absolute path to the kubeconfig file")
+	pflag.String("kubeconfig", defaultKubeconfig(), "(optional) absolute path to the kubeconfig file")
 }
 
 func parseFlags() {
@@ -73,7 +74,11 @@ func parseFlags() {
 // getConfig gets the kubernetes rest config.
 func getConfig() *rest.Config {
 	// use the current context in kubeconfig
-	config, err := clientcmd.BuildConfigFromFlags("", viper.GetString("kubeconfig"))
+	kubeconfig := viper.GetString("kubeconfig")
+	if kubeconfig == "" {
+		log.Fatal("Cannot determine homedir, pass in a kubeconfig location explicitly with --kubeconfig")
+	}
+	config, err := clientcmd.BuildConfigFromFlags("", kubeconfig)
 	if err != nil {
 		log.WithError(err).Fatal("Could not build kubeconfig")
 	}
@@ -91,12 +96,12 @@ func getClientset(config *rest.Config) *kubernetes.Clientset {
 	return clientset
 }
 
-func homeDir() string {
+func defaultKubeconfig() string {
 	hd, err := os.UserHomeDir()
-	if err != nil && !viper.IsSet("kubeconfig") {
-		log.Fatal("Cannot determine homedir, pass in a kubeconfig location explicitly with --kubeconfig")
+	if err != nil {
+		return ""
 	}
-	return hd
+	return filepath.Join(hd, ".kube", "config")
 }
 
 func generateDomainEntries() {
@@ -147,11 +152,22 @@ func watchForExternalIP(ch <-chan watch.Event, outCh chan<- svcInfo) error {
 					log.WithField("ing[0].Hostname", ing[0].Hostname).
 						Debug("Using Hostname")
 
-					ip, _ := net.LookupIP(ing[0].Hostname)
+					ips, err := lookupIP(ing[0].Hostname)
+					if err != nil {
+						log.WithError(err).
+							WithField("hostname", ing[0].Hostname).
+							Warn("Failed to resolve hostname")
+						continue
+					}
+					if len(ips) == 0 {
+						log.WithField("hostname", ing[0].Hostname).
+							Warn("Hostname did not resolve to any IPs")
+						continue
+					}
 
 					outCh <- svcInfo{
 						SvcName: svc.ObjectMeta.Name,
-						Addr:    ip[0].String(),
+						Addr:    ips[0].String(),
 					}
 				}
 			}

src/utils/dev_dns_updater/dev_dns_updater_test.go

@@ -0,0 +1,114 @@
+/*
+ * Copyright 2018- The Pixie Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package main
+
+import (
+	"errors"
+	"net"
+	"testing"
+
+	v1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/watch"
+)
+
+func TestWatchForExternalIPUsesResolvedHostname(t *testing.T) {
+	restoreDNSState := setTestDNSState()
+	defer restoreDNSState()
+
+	oldLookupIP := lookupIP
+	lookupIP = func(host string) ([]net.IP, error) {
+		if host != "example.com" {
+			t.Fatalf("unexpected hostname: %s", host)
+		}
+		return []net.IP{net.ParseIP("203.0.113.10")}, nil
+	}
+	defer func() { lookupIP = oldLookupIP }()
+
+	events := make(chan watch.Event, 1)
+	out := make(chan svcInfo, 1)
+	events <- serviceEvent("cloud-proxy-service", "", "example.com")
+	close(events)
+
+	if err := watchForExternalIP(events, out); err != nil {
+		t.Fatalf("watchForExternalIP returned error: %v", err)
+	}
+
+	got := <-out
+	if got.SvcName != "cloud-proxy-service" {
+		t.Fatalf("unexpected service name: %s", got.SvcName)
+	}
+	if got.Addr != "203.0.113.10" {
+		t.Fatalf("unexpected address: %s", got.Addr)
+	}
+}
+
+func TestWatchForExternalIPSkipsUnresolvedHostname(t *testing.T) {
+	restoreDNSState := setTestDNSState()
+	defer restoreDNSState()
+
+	oldLookupIP := lookupIP
+	lookupIP = func(host string) ([]net.IP, error) {
+		return nil, errors.New("lookup failed")
+	}
+	defer func() { lookupIP = oldLookupIP }()
+
+	events := make(chan watch.Event, 1)
+	out := make(chan svcInfo, 1)
+	events <- serviceEvent("cloud-proxy-service", "", "example.com")
+	close(events)
+
+	if err := watchForExternalIP(events, out); err != nil {
+		t.Fatalf("watchForExternalIP returned error: %v", err)
+	}
+
+	if len(out) != 0 {
+		t.Fatalf("expected no service updates, got %d", len(out))
+	}
+}
+
+func setTestDNSState() func() {
+	oldDNSEntries := dnsEntriesByService
+	dnsEntriesByService = map[string][]string{
+		"cloud-proxy-service": {"dev.withpixie.dev"},
+	}
+	return func() {
+		dnsEntriesByService = oldDNSEntries
+	}
+}
+
+func serviceEvent(name string, ip string, hostname string) watch.Event {
+	return watch.Event{
+		Object: &v1.Service{
+			ObjectMeta: metav1.ObjectMeta{
+				Name: name,
+			},
+			Status: v1.ServiceStatus{
+				LoadBalancer: v1.LoadBalancerStatus{
+					Ingress: []v1.LoadBalancerIngress{
+						{
+							IP:       ip,
+							Hostname: hostname,
+						},
+					},
+				},
+			},
+		},
+	}
+}