feat: add option to publish entries without namespace

Add an option to publish service entries without a namespace by
specifying `-without-namespace=true`.

This commit also changes the behavior to not append namespace for
hostnames specified on ingress resources. The hostnames specified on
the resource will be advertised as-is.

Resolves #1

Signed-off-by: Renan Rodrigues <renanqts@gmail.com>

Co-authored-by: Blake Covarrubias <blake@covarrubi.as>

README.md

@@ -18,7 +18,7 @@ LoadBalancer, will be advertised on the local network.
 
 By default External-mDNS will advertise hostnames for exposed resources in all
 namespaces. Use the `-namespace` flag to restrict advertisement to a single
-namespace.
+namespace, or `-without-namespace=true` for all namespaces.
 
 DNS records are advertised with the format `<hostname/service_name>.<namespace>.local`.
 In addition, hostnames for resources in the `-default-namespace` will also be

go.sum

@@ -31,7 +31,6 @@ github.com/go-openapi/swag v0.0.0-20160704191624-1d0bd113de87/go.mod h1:DXUve3Dp
 github.com/gogo/protobuf v1.3.1 h1:DqDEcV5aeaTmdFBePNpYsp3FlcVH/2ISVVM9Qf8PSls=
 github.com/gogo/protobuf v1.3.1/go.mod h1:SlYgWuQ5SjCEi6WLHjHCa1yvBfUnHcTbrrZtXPKa29o=
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
-github.com/golang/groupcache v0.0.0-20160516000752-02826c3e7903 h1:LbsanbbD6LieFkXbj9YNNBupiGHJgFeLpO0j0Fza1h8=
 github.com/golang/groupcache v0.0.0-20160516000752-02826c3e7903/go.mod h1:cIg4eruTrX1D+g88fzRXU5OdNfaM+9IcxsU14FzY7Hc=
 github.com/golang/groupcache v0.0.0-20190129154638-5b532d6fd5ef h1:veQD95Isof8w9/WXiA+pa3tz3fJXkt5B7QaRBrM62gk=
 github.com/golang/groupcache v0.0.0-20190129154638-5b532d6fd5ef/go.mod h1:cIg4eruTrX1D+g88fzRXU5OdNfaM+9IcxsU14FzY7Hc=
@@ -179,7 +178,6 @@ golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8T
 google.golang.org/api v0.4.0/go.mod h1:8k5glujaEP+g9n7WNsDg8QP6cUVNI86fCNMcbazEtwE=
 google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
 google.golang.org/appengine v1.4.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
-google.golang.org/appengine v1.5.0 h1:KxkO13IPW4Lslp2bz+KHP2E3gtFlrIGNThxkZQ3g+4c=
 google.golang.org/appengine v1.5.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
 google.golang.org/appengine v1.6.1 h1:QzqyMA1tlu6CgqCDUtU9V+ZKhLFT2dkJuANu5QaxI3I=
 google.golang.org/appengine v1.6.1/go.mod h1:i06prIuMbXzDqacNJfV5OdTW448YApPu5ww/cMBSeb0=

main.go

@@ -79,6 +79,17 @@ func lookupEnvOrInt(key string, defaultVal int) int {
 	return defaultVal
 }
 
+func lookupEnvOrBool(key string, defaultVal bool) bool {
+	if val, ok := os.LookupEnv(key); ok {
+		v, err := strconv.ParseBool(val)
+		if err != nil {
+			log.Fatalf("lookupEnvOrBool[%s]: %v", key, err)
+		}
+		return v
+	}
+	return defaultVal
+}
+
 func constructRecords(r resource.Resource) []string {
 	var records []string
 
@@ -90,10 +101,17 @@ func constructRecords(r resource.Resource) []string {
 	// Construct reverse IP
 	reverseIP := net.IPv4(ip[15], ip[14], ip[13], ip[12])
 
+	// Publish A records resources as <name>.<namespace>.local
+	// Ensure corresponding PTR records map to this hostname
 	records = append(records, fmt.Sprintf("%s.%s.local. %d IN A %s", r.Name, r.Namespace, recordTTL, ip))
 	records = append(records, fmt.Sprintf("%s.in-addr.arpa. %d IN PTR %s.%s.local.", reverseIP, recordTTL, r.Name, r.Namespace))
 
-	if r.Namespace == defaultNamespace {
+	// Publish services without the name in the namespace if any of the following
+	// criteria is satisfied:
+	// 1. The Service exists in the default namespace
+	// 2. The -without-namespace flag is equal to true
+	// 3. The record to be published is from an Ingress with a defined hostname
+	if r.Namespace == defaultNamespace || withoutNamespace || r.SourceType == "ingress" {
 		records = append(records, fmt.Sprintf("%s.local. %d IN A %s", r.Name, recordTTL, ip))
 	}
 
@@ -116,6 +134,7 @@ var (
 	master           = ""
 	namespace        = ""
 	defaultNamespace = "default"
+	withoutNamespace = false
 	test             = flag.Bool("test", false, "testing mode, no connection to k8s")
 	sourceFlag       k8sSource
 	kubeconfig       string
@@ -131,6 +150,7 @@ func main() {
 
 	// External-mDNS options
 	flag.StringVar(&defaultNamespace, "default-namespace", lookupEnvOrString("EXTERNAL_MDNS_DEFAULT_NAMESPACE", defaultNamespace), "Namespace in which services should also be published with a shorter entry")
+	flag.BoolVar(&withoutNamespace, "without-namespace", lookupEnvOrBool("EXTERNAL_MDNS_WITHOUT_NAMESPACE", withoutNamespace), "Published with a shorter entry without namespace (default: false)")
 	flag.StringVar(&namespace, "namespace", lookupEnvOrString("EXTERNAL_MDNS_NAMESPACE", namespace), "Limit sources of endpoints to a specific namespace (default: all namespaces)")
 	flag.Var(&sourceFlag, "source", "The resource types that are queried for endpoints; specify multiple times for multiple sources (required, options: service, ingress)")
 	flag.IntVar(&recordTTL, "record-ttl", lookupEnvOrInt("EXTERNAL_MDNS_RECORD_TTL", recordTTL), "DNS record time-to-live")

resource/resource.go

@@ -22,8 +22,9 @@ const (
 
 // Resource represents a resource to advertise over mDNS
 type Resource struct {
-	Action    string
-	IP        string
-	Name      string
-	Namespace string
+	SourceType string
+	Action     string
+	IP         string
+	Name       string
+	Namespace  string
 }

source/ingress.go

@@ -29,18 +29,17 @@ import (
 
 // IngressSource handles adding, updating, or removing mDNS record advertisements
 type IngressSource struct {
-	namespace       string
-	publishInternal bool
-	notifyChan      chan<- resource.Resource
-	sharedInformer  cache.SharedIndexInformer
+	namespace      string
+	notifyChan     chan<- resource.Resource
+	sharedInformer cache.SharedIndexInformer
 }
 
 // Run starts shared informers and waits for the shared informer cache to
 // synchronize.
 func (i *IngressSource) Run(stopCh chan struct{}) error {
 	i.sharedInformer.Run(stopCh)
 	if !cache.WaitForCacheSync(stopCh, i.sharedInformer.HasSynced) {
-		runtime.HandleError(fmt.Errorf("Timed out waiting for caches to sync"))
+		runtime.HandleError(fmt.Errorf("timed out waiting for caches to sync"))
 	}
 	return nil
 }
@@ -134,10 +133,11 @@ func (i *IngressSource) buildRecords(obj interface{}, action string) ([]resource
 			hostname = parsedHost.Domain
 		}
 		advertiseObj := resource.Resource{
-			Action:    action,
-			Name:      hostname,
-			Namespace: ingress.Namespace,
-			IP:        ipField,
+			SourceType: "ingress",
+			Action:     action,
+			Name:       hostname,
+			Namespace:  ingress.Namespace,
+			IP:         ipField,
 		}
 
 		records = append(records, advertiseObj)

source/service.go

@@ -37,7 +37,7 @@ type ServiceSource struct {
 func (s *ServiceSource) Run(stopCh chan struct{}) error {
 	s.sharedInformer.Run(stopCh)
 	if !cache.WaitForCacheSync(stopCh, s.sharedInformer.HasSynced) {
-		runtime.HandleError(fmt.Errorf("Timed out waiting for caches to sync"))
+		runtime.HandleError(fmt.Errorf("timed out waiting for caches to sync"))
 	}
 	return nil
 }
@@ -82,7 +82,8 @@ func (s *ServiceSource) onUpdate(oldObj interface{}, newObj interface{}) {
 func (s *ServiceSource) buildRecord(obj interface{}, action string) (resource.Resource, error) {
 
 	var advertiseObj = resource.Resource{
-		Action: action,
+		SourceType: "service",
+		Action:     action,
 	}
 
 	service, ok := obj.(*corev1.Service)