Discovery do not set default version

discovery/discovery.go

@@ -49,10 +49,6 @@ type ACIEndpoints []ACIEndpoint
 
 type PublicKeys []string
 
-const (
-	defaultVersion = "latest"
-)
-
 var (
 	templateExpression = regexp.MustCompile(`{.*?}`)
 	errEnough          = errors.New("enough discovery information found")
@@ -107,30 +103,33 @@ func extractACMeta(r io.Reader) []acMeta {
 	}
 }
 
-func renderTemplate(tpl string, kvs ...string) (string, bool) {
+func renderTemplate(tpl string, kvs ...string) (string, int, bool) {
+	count := 0
 	for i := 0; i < len(kvs); i += 2 {
 		k := kvs[i]
 		v := kvs[i+1]
+		if k != "{name}" && strings.Contains(tpl, k) {
+			count++
+		}
 		tpl = strings.Replace(tpl, k, v, -1)
 	}
-	return tpl, !templateExpression.MatchString(tpl)
+	return tpl, count, !templateExpression.MatchString(tpl)
 }
 
 func createTemplateVars(app App) []string {
 	tplVars := []string{"{name}", app.Name.String()}
-	// If a label is called "name", it will be ignored as it appears after
-	// in the slice
+	// Ignore labels called "name"
 	for n, v := range app.Labels {
+		if n == "name" {
+			continue
+		}
 		tplVars = append(tplVars, fmt.Sprintf("{%s}", n), v)
 	}
 	return tplVars
 }
 
 func doDiscover(pre string, hostHeaders map[string]http.Header, app App, insecure InsecureOption) (*discoveryData, error) {
 	app = *app.Copy()
-	if app.Labels["version"] == "" {
-		app.Labels["version"] = defaultVersion
-	}
 
 	_, body, err := httpsOrHTTP(pre, hostHeaders, insecure)
 	if err != nil {
@@ -144,6 +143,7 @@ func doDiscover(pre string, hostHeaders map[string]http.Header, app App, insecur
 
 	dd := &discoveryData{}
 
+	bestCount := 0
 	for _, m := range meta {
 		if !strings.HasPrefix(app.Name.String(), m.prefix) {
 			continue
@@ -152,16 +152,22 @@ func doDiscover(pre string, hostHeaders map[string]http.Header, app App, insecur
 		switch m.name {
 		case "ac-discovery":
 			// Ignore not handled variables as {ext} isn't already rendered.
-			uri, _ := renderTemplate(m.uri, tplVars...)
-			asc, ok := renderTemplate(uri, "{ext}", "aci.asc")
+			uri, count, _ := renderTemplate(m.uri, tplVars...)
+			asc, _, ok := renderTemplate(uri, "{ext}", "aci.asc")
 			if !ok {
 				continue
 			}
-			aci, ok := renderTemplate(uri, "{ext}", "aci")
+			aci, _, ok := renderTemplate(uri, "{ext}", "aci")
 			if !ok {
 				continue
 			}
-			dd.ACIEndpoints = append(dd.ACIEndpoints, ACIEndpoint{ACI: aci, ASC: asc})
+
+			if count > bestCount {
+				dd.ACIEndpoints = ACIEndpoints{ACIEndpoint{ACI: aci, ASC: asc}}
+				bestCount = count
+			} else if count == bestCount {
+				dd.ACIEndpoints = append(dd.ACIEndpoints, ACIEndpoint{ACI: aci, ASC: asc})
+			}
 
 		case "ac-discovery-pubkeys":
 			dd.PublicKeys = append(dd.PublicKeys, m.uri)

discovery/discovery_test.go

@@ -402,8 +402,7 @@ func TestDiscoverEndpoints(t *testing.T) {
 			[]string{"https://example.com/pubkeys.gpg"},
 			nil,
 		},
-		// Test missing labels. version label should default to
-		// "latest" and the first template should be rendered
+		// Test missing labels. No template will render
 		{
 			&mockHTTPDoer{
 				doer: fakeHTTPGet(
@@ -415,18 +414,13 @@ func TestDiscoverEndpoints(t *testing.T) {
 					nil,
 				),
 			},
-			true,
+			false,
 			true,
 			App{
 				Name:   "example.com/myapp",
 				Labels: map[types.ACIdentifier]string{},
 			},
-			[]ACIEndpoint{
-				ACIEndpoint{
-					ACI: "https://storage.example.com/example.com/myapp-latest.aci",
-					ASC: "https://storage.example.com/example.com/myapp-latest.aci.asc",
-				},
-			},
+			[]ACIEndpoint{},
 			[]string{"https://example.com/pubkeys.gpg"},
 			nil,
 		},
@@ -461,6 +455,7 @@ func TestDiscoverEndpoints(t *testing.T) {
 			nil,
 		},
 		// Test multiple ACIEndpoints.
+		// Should render the first two endpoint, since the others match less labels
 		{
 			&mockHTTPDoer{
 				doer: fakeHTTPGet(
@@ -488,12 +483,144 @@ func TestDiscoverEndpoints(t *testing.T) {
 					ASC: "https://storage.example.com/example.com/myapp-1.0.0-linux-amd64.aci.asc",
 				},
 				ACIEndpoint{
-					ACI: "https://storage.example.com/example.com/myapp-1.0.0.aci",
-					ASC: "https://storage.example.com/example.com/myapp-1.0.0.aci.asc",
+					ACI: "https://mirror.storage.example.com/example.com/myapp-1.0.0-linux-amd64.aci",
+					ASC: "https://mirror.storage.example.com/example.com/myapp-1.0.0-linux-amd64.aci.asc",
+				},
+			},
+			[]string{"https://example.com/pubkeys.gpg"},
+			nil,
+		},
+		// Test multiple ACIEndpoints.
+		// Should render endpoint 3 and 4, since the 1 and 2 doesn't fully render and the others match less labels
+		// Example noarch versioned matching
+		{
+			&mockHTTPDoer{
+				doer: fakeHTTPGet(
+					[]meta{
+						{"/myapp",
+							"meta06.html",
+						},
+					},
+					nil,
+				),
+			},
+			true,
+			true,
+			App{
+				Name: "example.com/myapp",
+				Labels: map[types.ACIdentifier]string{
+					"version": "1.0.0",
+				},
+			},
+			[]ACIEndpoint{
+				ACIEndpoint{
+					ACI: "https://storage.example.com/example.com/myapp-1.0.0-noarch.aci",
+					ASC: "https://storage.example.com/example.com/myapp-1.0.0-noarch.aci.asc",
+				},
+				ACIEndpoint{
+					ACI: "https://mirror.storage.example.com/example.com/myapp-1.0.0-noarch.aci",
+					ASC: "https://mirror.storage.example.com/example.com/myapp-1.0.0-noarch.aci.asc",
+				},
+			},
+			[]string{"https://example.com/pubkeys.gpg"},
+			nil,
+		},
+		// Test multiple ACIEndpoints.
+		// Should render endpoint 5 and 6, since the 1, 2, 3, 4 doesn't fully render and the others match less labels
+		// Example latest matching
+		{
+			&mockHTTPDoer{
+				doer: fakeHTTPGet(
+					[]meta{
+						{"/myapp",
+							"meta06.html",
+						},
+					},
+					nil,
+				),
+			},
+			true,
+			true,
+			App{
+				Name: "example.com/myapp",
+				Labels: map[types.ACIdentifier]string{
+					"os":   "linux",
+					"arch": "amd64",
 				},
+			},
+			[]ACIEndpoint{
+				ACIEndpoint{
+					ACI: "https://storage.example.com/example.com/myapp-latest-linux-amd64.aci",
+					ASC: "https://storage.example.com/example.com/myapp-latest-linux-amd64.aci.asc",
+				},
+				ACIEndpoint{
+					ACI: "https://mirror.storage.example.com/example.com/myapp-latest-linux-amd64.aci",
+					ASC: "https://mirror.storage.example.com/example.com/myapp-latest-linux-amd64.aci.asc",
+				},
+			},
+			[]string{"https://example.com/pubkeys.gpg"},
+			nil,
+		},
+		// Test multiple ACIEndpoints.
+		// Should render endpoint 7 and 8, since the others don't fully render.
+		// Example noarch latest matching
+		{
+			&mockHTTPDoer{
+				doer: fakeHTTPGet(
+					[]meta{
+						{"/myapp",
+							"meta06.html",
+						},
+					},
+					nil,
+				),
+			},
+			true,
+			true,
+			App{
+				Name:   "example.com/myapp",
+				Labels: map[types.ACIdentifier]string{},
+			},
+			[]ACIEndpoint{
+				ACIEndpoint{
+					ACI: "https://storage.example.com/example.com/myapp-latest-noarch.aci",
+					ASC: "https://storage.example.com/example.com/myapp-latest-noarch.aci.asc",
+				},
+				ACIEndpoint{
+					ACI: "https://mirror.storage.example.com/example.com/myapp-latest-noarch.aci",
+					ASC: "https://mirror.storage.example.com/example.com/myapp-latest-noarch.aci.asc",
+				},
+			},
+			[]string{"https://example.com/pubkeys.gpg"},
+			nil,
+		},
+
+		// Test a discovery string that has an hardcoded app name instead of using the provided {name}
+		{
+			&mockHTTPDoer{
+				doer: fakeHTTPGet(
+					[]meta{
+						{"/myapp",
+							"meta07.html",
+						},
+					},
+					nil,
+				),
+			},
+			true,
+			true,
+			App{
+				Name: "example.com/myapp",
+				Labels: map[types.ACIdentifier]string{
+					"version": "1.0.0",
+					"os":      "linux",
+					"arch":    "amd64",
+				},
+			},
+			[]ACIEndpoint{
 				ACIEndpoint{
-					ACI: "hdfs://storage.example.com/example.com/myapp-1.0.0-linux-amd64.aci",
-					ASC: "hdfs://storage.example.com/example.com/myapp-1.0.0-linux-amd64.aci.asc",
+					ACI: "https://storage.example.com/myapp-1.0.0-linux-amd64.aci",
+					ASC: "https://storage.example.com/myapp-1.0.0-linux-amd64.aci.asc",
 				},
 			},
 			[]string{"https://example.com/pubkeys.gpg"},

discovery/testdata/meta06.html

@@ -3,9 +3,19 @@
 <html>
 <head>
 	<title>My app</title>
+	<!-- ACIs with specific version -->
 	<meta name="ac-discovery" content="example.com https://storage.example.com/{name}-{version}-{os}-{arch}.{ext}">
-	<meta name="ac-discovery" content="example.com https://storage.example.com/{name}-{version}.{ext}">
-	<meta name="ac-discovery" content="example.com hdfs://storage.example.com/{name}-{version}-{os}-{arch}.{ext}">
+	<meta name="ac-discovery" content="example.com https://mirror.storage.example.com/{name}-{version}-{os}-{arch}.{ext}">
+	<!-- noarch ACIs -->
+	<meta name="ac-discovery" content="example.com https://storage.example.com/{name}-{version}-noarch.{ext}">
+	<meta name="ac-discovery" content="example.com https://mirror.storage.example.com/{name}-{version}-noarch.{ext}">
+	<!-- Latest ACIs -->
+	<meta name="ac-discovery" content="example.com https://storage.example.com/{name}-latest-{os}-{arch}.{ext}">
+	<meta name="ac-discovery" content="example.com https://mirror.storage.example.com/{name}-latest-{os}-{arch}.{ext}">
+	<!-- Latest noarch ACIs -->
+	<meta name="ac-discovery" content="example.com https://storage.example.com/{name}-latest-noarch.{ext}">
+	<meta name="ac-discovery" content="example.com https://mirror.storage.example.com/{name}-latest-noarch.{ext}">
+
 	<meta name="ac-discovery-pubkeys" content="example.com https://example.com/pubkeys.gpg">
 </head>
 

discovery/testdata/meta07.html

@@ -0,0 +1,13 @@
+<!DOCTYPE html>
+
+<html>
+<head>
+	<title>My app</title>
+	<meta name="ac-discovery" content="example.com/myapp https://storage.example.com/myapp-{version}-{os}-{arch}.{ext}">
+	<meta name="ac-discovery-pubkeys" content="example.com https://example.com/pubkeys.gpg">
+</head>
+
+<body>
+	<h1>My App</h1>
+</body>
+</html>

spec/discovery.md

@@ -59,6 +59,18 @@ curl $(echo "$urltmpl" | sed -e "s/{name}/$name/" -e "s/{version}/$version/" -e
 
 where _name_, _version_, _os_, and _arch_ are set to their respective values for the image, and _ext_ is either `aci` or `aci.asc` for retrieving an App Container Image or signature respectively.
 
+The client MUST accept only best matching templates. Best matching templates are the one where all the templates labels can be substituted and with the highest number of substituted labels.
+
+For example given these meta tags:
+```html
+<meta name="ac-discovery" content="example.com https://storage.example.com/{os}/{arch}/{name}-{version}.{ext}">
+<meta name="ac-discovery" content="example.com https://mirror.storage.example.com/{os}/{arch}/{name}-{version}.{ext}">
+<meta name="ac-discovery" content="example.com https://storage.example.com/{os}/{arch}/{name}-latest.{ext}">
+```
+
+If the client requires the image name _name_ and labels _version_, _os_, _arch_ only the first two templates will be rendered since they match 3 labels (while the the last matches only 2 labels since it doesn't match the _version_ label).
+If the client requires the image name _name_ and labels _os_, _arch_ only the last template will be rendered since in the first template '{version}' cannot be substituted.
+
 Note that multiple `ac-discovery` tags MAY be returned for a given prefix-match (for example, with different scheme names representing different transport mechanisms).
 In this case, the client implementation MAY choose which to use at its own discretion.
 Public discovery implementations SHOULD always provide at least one HTTPS URL template.
@@ -95,3 +107,19 @@ Authentication during the discovery process is optional.
 If an attempt at fetching any resource (the initial discovery URL, an App Container Image, or signature) returns a `401 Unauthorized`, implementations should enact the authentication policy set by the operator.
 For example, some implementations might only perform HTTP basic authentication over HTTPS connections.
 
+
+### Examples
+
+#### Latest pattern
+
+If a client wants to retrieve the latest available ACI (without knowing its version) it can provide these meta tags:
+
+```html
+<meta name="ac-discovery" content="example.com https://storage.example.com/{os}/{arch}/{name}-{version}.{ext}">
+<meta name="ac-discovery" content="example.com https://storage.example.com/{os}/{arch}/{name}-latest.{ext}">
+```
+
+When requiring a specific version, the first template will be rendered, when not requiring a _version_ label the second template will match.
+
+On the http server, the "latest" url should point to the current latest ACI.
+