discovery: add port parameter

Currently the ACI spec only supports discovery on ports 80 and 443, this
does not allow using a discovery server in any other ports.

Fix the problem by adding support for arbitrary ports when querying a
discovery server.

fixes rkt/rkt#365

SPEC.md

@@ -245,7 +245,15 @@ For example, if the ACE is looking for `example.com/reduce-worker` it will reque
 
     https://example.com/reduce-worker?ac-discovery=1
 
-Then inspect the HTML returned for meta tags that have the following format:
+As a convenience feature, trying to fetch an app container image with a port number, will assume that the discovery server is listening in this port.
+
+For example, if the ACE is looking for `example.com:8080/reduce-worker` it will request:
+
+    https://example.com:8080/reduce-worker?ac-discovery=1
+
+**Note**: the app name is still considered as `example.com/reduce-worker`
+
+After requesting it, inspect the HTML returned for meta tags that have the following format:
 
 ```
 <meta name="ac-discovery" content="prefix-match url-tmpl">

actool/discover.go

@@ -28,12 +28,13 @@ func runDiscover(args []string) (exit int) {
 	}
 
 	for _, name := range args {
-		app, err := discovery.NewAppFromString(name)
+		nameWithoutPort, port := discovery.ExtractPort(name)
+		app, err := discovery.NewAppFromString(nameWithoutPort)
 		if err != nil {
 			stderr("%s: %s", name, err)
 			return 1
 		}
-		eps, err := discovery.DiscoverEndpoints(*app, transportFlags.Insecure)
+		eps, err := discovery.DiscoverEndpoints(*app, port, transportFlags.Insecure)
 
 		if err != nil {
 			stderr("error fetching %s: %s", name, err)

discovery/discovery.go

@@ -148,8 +148,11 @@ func doDiscover(app App, pre string, insecure bool) (*Endpoints, error) {
 // DiscoverEndpoints will make HTTPS requests to find the ac-discovery meta
 // tags and optionally will use HTTP if insecure is set. Based on the app
 // passed the discovery templates will be filled out and returned in eps.
-func DiscoverEndpoints(app App, insecure bool) (eps *Endpoints, err error) {
+func DiscoverEndpoints(app App, port string, insecure bool) (eps *Endpoints, err error) {
 	parts := strings.Split(string(app.Name), "/")
+	if port != "" {
+		parts[0] += ":" + port
+	}
 	for i := range parts {
 		end := len(parts) - i
 		pre := strings.Join(parts[:end], "/")

discovery/discovery_test.go

@@ -158,7 +158,7 @@ func TestDiscoverEndpoints(t *testing.T) {
 
 	for i, tt := range tests {
 		httpGet = tt.get
-		de, err := DiscoverEndpoints(tt.app, true)
+		de, err := DiscoverEndpoints(tt.app, "", true)
 		if err != nil && !tt.expectDiscoverySuccess {
 			continue
 		}

discovery/parse.go

@@ -27,6 +27,19 @@ func NewApp(name string, labels map[string]string) (*App, error) {
 	}, nil
 }
 
+func ExtractPort(name string) (nameWithoutPort string, port string) {
+	nameParts := strings.SplitN(name, "/", 2)
+	hostParts := strings.Split(nameParts[0], ":")
+	port = ""
+	if len(hostParts) > 1 {
+		port = hostParts[1]
+	}
+	// discard port in img since it's not part of an app name
+	nameWithoutPort = hostParts[0] + "/" + nameParts[1]
+
+	return nameWithoutPort, port
+}
+
 // NewAppFromString takes a command line app parameter and returns a map of labels.
 //
 // Example app parameters: