registry: do not cache image metadata for latest and edge tags

internal/registry/image.go

@@ -7,6 +7,7 @@ package registry
 import (
 	"crypto/tls"
 	"encoding/json"
+	"fmt"
 	"net/http"
 	"strings"
 	"sync"
@@ -59,25 +60,27 @@ func (r *imageMetadataRetriever) cachedLabels(image string) (map[string]string,
 		return r.labelsCache[image], nil
 	}
 
-	labels, err := r.imageLabels(image)
+	parts := parseImage(image)
+	labels, err := r.imageLabels(parts)
 	if err != nil {
 		return nil, err
 	}
-	r.labelsCache[image] = labels
+	if !parts.isLatest() {
+		r.labelsCache[image] = labels
+	}
 
 	return labels, nil
 }
 
-func (r *imageMetadataRetriever) imageLabels(image string) (map[string]string, error) {
+func (r *imageMetadataRetriever) imageLabels(image dockerImage) (map[string]string, error) {
 	type historyEntry struct {
 		Config struct {
 			Labels map[string]string
 		}
 	}
 
-	parts := parseImage(image)
-	hub := r.registry(parts.registry)
-	manifest, err := hub.Manifest(parts.image, parts.tag)
+	hub := r.registry(image.registry)
+	manifest, err := hub.Manifest(image.image, image.tag)
 	if err != nil {
 		return nil, err
 	}
@@ -126,9 +129,18 @@ type dockerImage struct {
 	tag      string
 }
 
+func (i dockerImage) isLatest() bool {
+	return i.tag == "latest" || i.tag == "edge"
+}
+
+func (i dockerImage) String() string {
+	return fmt.Sprintf("%s/%s:%s", i.registry, i.image, i.tag)
+}
+
 func parseImage(imageName string) dockerImage {
 	img := dockerImage{
 		registry: "registry-1.docker.io",
+		tag:      "latest",
 	}
 
 	parts := strings.SplitN(imageName, "/", 3)

internal/registry/image_test.go

@@ -1,6 +1,7 @@
 package registry
 
 import (
+	"fmt"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -12,22 +13,15 @@ import (
 )
 
 func TestImageMetadataRetriever_Modules(t *testing.T) {
-	r := NewImageMetadata()
-	r.insecure = true
+	var apiCalls []string
+	var labels string
 	srv := httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		assert.Equal(t, "/v2/my/img/manifests/v1", r.URL.Path)
-		assert.Equal(t, "GET", r.Method)
-		w.Header().Add("Content-Type", "application/vnd.docker.distribution.manifest.v1+json")
+		apiCalls = append(apiCalls, r.URL.Path)
 		sig, err := libtrust.NewJSONSignatureFromMap(map[string]interface{}{
-			"schemaVersion": 1,
-			"name":          "my/img",
-			"tag":           "v1",
 			"history": []map[string]interface{}{{
-				"v1Compatibility": `{
-					"config":{
-						"Labels":{"io.tsuru.nginx-modules":"mod1,mod2"}
-					}
-				}`,
+				"v1Compatibility": fmt.Sprintf(`{
+					"config":{%s}
+				}`, labels),
 			}},
 		})
 		require.NoError(t, err)
@@ -42,9 +36,76 @@ func TestImageMetadataRetriever_Modules(t *testing.T) {
 	defer srv.Close()
 	u, err := url.Parse(srv.URL)
 	require.NoError(t, err)
-	mod, err := r.Modules(u.Host + "/my/img:v1")
-	require.NoError(t, err)
-	assert.Equal(t, []string{"mod1", "mod2"}, mod)
+
+	tests := []struct {
+		image           string
+		labels          string
+		expectedModules []string
+		expectedCalls   []string
+	}{
+		{
+			image:           "my/img:v1",
+			expectedModules: nil,
+			expectedCalls:   []string{"/v2/my/img/manifests/v1"},
+		},
+		{
+			image:           "my/img:v1",
+			labels:          `"Labels":{"io.tsuru.nginx-modules":"mod1,mod2"}`,
+			expectedModules: []string{"mod1", "mod2"},
+			expectedCalls:   []string{"/v2/my/img/manifests/v1"},
+		},
+		{
+			image:           "my/img:latest",
+			expectedModules: nil,
+			expectedCalls:   []string{"/v2/my/img/manifests/latest", "/v2/my/img/manifests/latest"},
+		},
+		{
+			image:           "my/img:edge",
+			expectedModules: nil,
+			expectedCalls:   []string{"/v2/my/img/manifests/edge", "/v2/my/img/manifests/edge"},
+		},
+		{
+			image:           "my/img:v1",
+			labels:          `"Labels":{}`,
+			expectedModules: nil,
+			expectedCalls:   []string{"/v2/my/img/manifests/v1"},
+		},
+		{
+			image:           "my/img:v1",
+			labels:          `"Labels":null`,
+			expectedModules: nil,
+			expectedCalls:   []string{"/v2/my/img/manifests/v1"},
+		},
+		{
+			image:           "my/img:v1",
+			labels:          `"Labels":{"other":"mod1,mod2"}`,
+			expectedModules: nil,
+			expectedCalls:   []string{"/v2/my/img/manifests/v1"},
+		},
+		{
+			image:           "my/img:v1",
+			labels:          `"Labels":{"io.tsuru.nginx-modules":""}`,
+			expectedModules: nil,
+			expectedCalls:   []string{"/v2/my/img/manifests/v1"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run("", func(t *testing.T) {
+			apiCalls = nil
+			labels = tt.labels
+			r := NewImageMetadata()
+			r.insecure = true
+			mod, err := r.Modules(u.Host + "/" + tt.image)
+			require.NoError(t, err)
+			assert.Equal(t, tt.expectedModules, mod)
+			mod, err = r.Modules(u.Host + "/" + tt.image)
+			require.NoError(t, err)
+			assert.Equal(t, tt.expectedModules, mod)
+			assert.Equal(t, tt.expectedCalls, apiCalls)
+
+		})
+	}
 }
 
 func TestParseImage(t *testing.T) {
@@ -54,11 +115,11 @@ func TestParseImage(t *testing.T) {
 		expectedImage    string
 		expectedTag      string
 	}{
-		{"f064bf4", "registry-1.docker.io", "f064bf4", ""},
-		{"", "registry-1.docker.io", "", ""},
+		{"f064bf4", "registry-1.docker.io", "f064bf4", "latest"},
+		{"", "registry-1.docker.io", "", "latest"},
 		{"registry.io/tsuru/app-img:v1", "registry.io", "tsuru/app-img", "v1"},
 		{"tsuru/app-img:v1", "registry-1.docker.io", "tsuru/app-img", "v1"},
-		{"tsuru/app-img", "registry-1.docker.io", "tsuru/app-img", ""},
+		{"tsuru/app-img", "registry-1.docker.io", "tsuru/app-img", "latest"},
 		{"f064bf4:v1", "registry-1.docker.io", "f064bf4", "v1"},
 		{"registry:5000/app-img:v1", "registry:5000", "app-img", "v1"},
 		{"registry.io/app-img:v1", "registry.io", "app-img", "v1"},