adding downward api volume plugin

pkg/fieldpath/fieldpath.go

@@ -22,6 +22,15 @@ import (
 	"k8s.io/kubernetes/pkg/api/meta"
 )
 
+// formatMap formats map[string]string to a string.
+func formatMap(m map[string]string) string {
+	var l string
+	for key, value := range m {
+		l += key + "=" + fmt.Sprintf("%q", value) + "\n"
+	}
+	return l
+}
+
 // ExtractFieldPathAsString extracts the field from the given object
 // and returns it as a string.  The object must be a pointer to an
 // API type.
@@ -37,6 +46,10 @@ func ExtractFieldPathAsString(obj interface{}, fieldPath string) (string, error)
 	}
 
 	switch fieldPath {
+	case "metadata.annotations":
+		return formatMap(accessor.Annotations()), nil
+	case "metadata.labels":
+		return formatMap(accessor.Labels()), nil
 	case "metadata.name":
 		return accessor.Name(), nil
 	case "metadata.namespace":

pkg/fieldpath/fieldpath_test.go

@@ -57,6 +57,37 @@ func TestExtractFieldPathAsString(t *testing.T) {
 			},
 			expectedValue: "object-name",
 		},
+		{
+			name:      "ok - labels",
+			fieldPath: "metadata.labels",
+			obj: &api.Pod{
+				ObjectMeta: api.ObjectMeta{
+					Labels: map[string]string{"key": "value"},
+				},
+			},
+			expectedValue: "key=\"value\"\n",
+		},
+		{
+			name:      "ok - labels bslash n",
+			fieldPath: "metadata.labels",
+			obj: &api.Pod{
+				ObjectMeta: api.ObjectMeta{
+					Labels: map[string]string{"key": "value\n"},
+				},
+			},
+			expectedValue: "key=\"value\\n\"\n",
+		},
+		{
+			name:      "ok - annotations",
+			fieldPath: "metadata.annotations",
+			obj: &api.Pod{
+				ObjectMeta: api.ObjectMeta{
+					Annotations: map[string]string{"builder": "john-doe"},
+				},
+			},
+			expectedValue: "builder=\"john-doe\"\n",
+		},
+
 		{
 			name:      "invalid expression",
 			fieldPath: "metadata.whoops",