Expose single annotation/label via downward API

hack/import-restrictions.yaml

@@ -4,6 +4,7 @@
   - k8s.io/apiserver/pkg/util/feature
   - k8s.io/kubernetes/pkg/apis/core
   - k8s.io/kubernetes/pkg/features
+  - k8s.io/kubernetes/pkg/fieldpath
   - k8s.io/kubernetes/pkg/util
   - k8s.io/api/core/v1
 

pkg/apis/core/v1/BUILD

@@ -16,6 +16,7 @@ go_library(
         "//pkg/apis/core:go_default_library",
         "//pkg/apis/extensions:go_default_library",
         "//pkg/features:go_default_library",
+        "//pkg/fieldpath:go_default_library",
         "//pkg/util/parsers:go_default_library",
         "//pkg/util/pointer:go_default_library",
         "//vendor/k8s.io/api/core/v1:go_default_library",

pkg/apis/core/v1/conversion.go

@@ -28,6 +28,7 @@ import (
 	"k8s.io/apimachinery/pkg/util/validation/field"
 	"k8s.io/kubernetes/pkg/apis/core"
 	"k8s.io/kubernetes/pkg/apis/extensions"
+	"k8s.io/kubernetes/pkg/fieldpath"
 )
 
 // This is a "fast-path" that avoids reflection for common types. It focuses on the objects that are
@@ -156,7 +157,8 @@ func addConversionFuncs(scheme *runtime.Scheme) error {
 	// Add field conversion funcs.
 	err = scheme.AddFieldLabelConversionFunc("v1", "Pod",
 		func(label, value string) (string, string, error) {
-			switch label {
+			path, _ := fieldpath.SplitMaybeSubscriptedPath(label)
+			switch path {
 			case "metadata.annotations",
 				"metadata.labels",
 				"metadata.name",

pkg/apis/core/validation/BUILD

@@ -22,6 +22,7 @@ go_library(
         "//pkg/apis/core/v1/helper:go_default_library",
         "//pkg/capabilities:go_default_library",
         "//pkg/features:go_default_library",
+        "//pkg/fieldpath:go_default_library",
         "//pkg/security/apparmor:go_default_library",
         "//vendor/github.com/golang/glog:go_default_library",
         "//vendor/k8s.io/api/core/v1:go_default_library",

pkg/apis/core/validation/validation.go

@@ -50,6 +50,7 @@ import (
 	v1helper "k8s.io/kubernetes/pkg/apis/core/v1/helper"
 	"k8s.io/kubernetes/pkg/capabilities"
 	"k8s.io/kubernetes/pkg/features"
+	"k8s.io/kubernetes/pkg/fieldpath"
 	"k8s.io/kubernetes/pkg/security/apparmor"
 )
 
@@ -960,11 +961,13 @@ func validateFlockerVolumeSource(flocker *core.FlockerVolumeSource, fldPath *fie
 	return allErrs
 }
 
-var validDownwardAPIFieldPathExpressions = sets.NewString(
+var validVolumeDownwardAPIFieldPathExpressions = sets.NewString(
 	"metadata.name",
 	"metadata.namespace",
 	"metadata.labels",
+	"metadata.labels[]", // represents "metadata.labels" with an arbitary subscript
 	"metadata.annotations",
+	"metadata.annotations[]", // represents "metadata.annotations" with an arbitary subscript
 	"metadata.uid")
 
 func validateDownwardAPIVolumeFile(file *core.DownwardAPIVolumeFile, fldPath *field.Path) field.ErrorList {
@@ -975,7 +978,7 @@ func validateDownwardAPIVolumeFile(file *core.DownwardAPIVolumeFile, fldPath *fi
 	}
 	allErrs = append(allErrs, validateLocalNonReservedPath(file.Path, fldPath.Child("path"))...)
 	if file.FieldRef != nil {
-		allErrs = append(allErrs, validateObjectFieldSelector(file.FieldRef, &validDownwardAPIFieldPathExpressions, fldPath.Child("fieldRef"))...)
+		allErrs = append(allErrs, validateObjectFieldSelector(file.FieldRef, &validVolumeDownwardAPIFieldPathExpressions, fldPath.Child("fieldRef"))...)
 		if file.ResourceFieldRef != nil {
 			allErrs = append(allErrs, field.Invalid(fldPath, "resource", "fieldRef and resourceFieldRef can not be specified simultaneously"))
 		}
@@ -1898,7 +1901,16 @@ func ValidateEnv(vars []core.EnvVar, fldPath *field.Path) field.ErrorList {
 	return allErrs
 }
 
-var validFieldPathExpressionsEnv = sets.NewString("metadata.name", "metadata.namespace", "metadata.uid", "spec.nodeName", "spec.serviceAccountName", "status.hostIP", "status.podIP")
+var validEnvDownwardAPIFieldPathExpressions = sets.NewString(
+	"metadata.annotations[]", // represents "metadata.annotations" with an arbitary subscript
+	"metadata.labels[]",      // represents "metadata.labels" with an arbitary subscript
+	"metadata.name",
+	"metadata.namespace",
+	"metadata.uid",
+	"spec.nodeName",
+	"spec.serviceAccountName",
+	"status.hostIP",
+	"status.podIP")
 var validContainerResourceFieldPathExpressions = sets.NewString("limits.cpu", "limits.memory", "limits.ephemeral-storage", "requests.cpu", "requests.memory", "requests.ephemeral-storage")
 
 func validateEnvVarValueFrom(ev core.EnvVar, fldPath *field.Path) field.ErrorList {
@@ -1912,7 +1924,7 @@ func validateEnvVarValueFrom(ev core.EnvVar, fldPath *field.Path) field.ErrorLis
 
 	if ev.ValueFrom.FieldRef != nil {
 		numSources++
-		allErrs = append(allErrs, validateObjectFieldSelector(ev.ValueFrom.FieldRef, &validFieldPathExpressionsEnv, fldPath.Child("fieldRef"))...)
+		allErrs = append(allErrs, validateObjectFieldSelector(ev.ValueFrom.FieldRef, &validEnvDownwardAPIFieldPathExpressions, fldPath.Child("fieldRef"))...)
 	}
 	if ev.ValueFrom.ResourceFieldRef != nil {
 		numSources++
@@ -1945,14 +1957,32 @@ func validateObjectFieldSelector(fs *core.ObjectFieldSelector, expressions *sets
 
 	if len(fs.APIVersion) == 0 {
 		allErrs = append(allErrs, field.Required(fldPath.Child("apiVersion"), ""))
-	} else if len(fs.FieldPath) == 0 {
+		return allErrs
+	}
+	if len(fs.FieldPath) == 0 {
 		allErrs = append(allErrs, field.Required(fldPath.Child("fieldPath"), ""))
-	} else {
+		return allErrs
+	}
+
 	internalFieldPath, _, err := legacyscheme.Scheme.ConvertFieldLabel(fs.APIVersion, "Pod", fs.FieldPath, "")
 	if err != nil {
 		allErrs = append(allErrs, field.Invalid(fldPath.Child("fieldPath"), fs.FieldPath, fmt.Sprintf("error converting fieldPath: %v", err)))
-		} else if !expressions.Has(internalFieldPath) {
+		return allErrs
-			allErrs = append(allErrs, field.NotSupported(fldPath.Child("fieldPath"), internalFieldPath, expressions.List()))
+	}
+
+	path, subscript := fieldpath.SplitMaybeSubscriptedPath(internalFieldPath)
+	if len(subscript) > 0 {
+		// This is to indicate that the internalFieldPath has a subscript, so
+		// that we can compare the path against the allowed path set easily.
+		path += "[]"
+	}
+	if !expressions.Has(path) {
+		allErrs = append(allErrs, field.NotSupported(fldPath.Child("fieldPath"), path, expressions.List()))
+		return allErrs
+	}
+	if len(subscript) > 0 {
+		for _, msg := range validation.IsQualifiedName(subscript) {
+			allErrs = append(allErrs, field.Invalid(fldPath, subscript, msg))
 		}
 	}
 

pkg/apis/core/validation/validation_test.go

@@ -2628,6 +2628,13 @@ func TestValidateVolumes(t *testing.T) {
 									FieldPath:  "metadata.labels",
 								},
 							},
+							{
+								Path: "labels with subscript",
+								FieldRef: &core.ObjectFieldSelector{
+									APIVersion: "v1",
+									FieldPath:  "metadata.labels['key']",
+								},
+							},
 							{
 								Path: "annotations",
 								FieldRef: &core.ObjectFieldSelector{
@@ -2635,6 +2642,13 @@ func TestValidateVolumes(t *testing.T) {
 									FieldPath:  "metadata.annotations",
 								},
 							},
+							{
+								Path: "annotations with subscript",
+								FieldRef: &core.ObjectFieldSelector{
+									APIVersion: "v1",
+									FieldPath:  "metadata.annotations['key']",
+								},
+							},
 							{
 								Path: "namespace",
 								FieldRef: &core.ObjectFieldSelector{
@@ -3824,6 +3838,24 @@ func TestValidateEnv(t *testing.T) {
 		{Name: "abc", Value: ""},
 		{Name: "a.b.c", Value: "value"},
 		{Name: "a-b-c", Value: "value"},
+		{
+			Name: "abc",
+			ValueFrom: &core.EnvVarSource{
+				FieldRef: &core.ObjectFieldSelector{
+					APIVersion: legacyscheme.Registry.GroupOrDie(core.GroupName).GroupVersion.String(),
+					FieldPath:  "metadata.annotations['key']",
+				},
+			},
+		},
+		{
+			Name: "abc",
+			ValueFrom: &core.EnvVarSource{
+				FieldRef: &core.ObjectFieldSelector{
+					APIVersion: legacyscheme.Registry.GroupOrDie(core.GroupName).GroupVersion.String(),
+					FieldPath:  "metadata.labels['key']",
+				},
+			},
+		},
 		{
 			Name: "abc",
 			ValueFrom: &core.EnvVarSource{
@@ -4095,7 +4127,20 @@ func TestValidateEnv(t *testing.T) {
 			expectedError: `[0].valueFrom.fieldRef.fieldPath: Invalid value: "metadata.whoops": error converting fieldPath`,
 		},
 		{
-			name: "invalid fieldPath labels",
+			name: "metadata.name with subscript",
+			envs: []core.EnvVar{{
+				Name: "labels",
+				ValueFrom: &core.EnvVarSource{
+					FieldRef: &core.ObjectFieldSelector{
+						FieldPath:  "metadata.name['key']",
+						APIVersion: "v1",
+					},
+				},
+			}},
+			expectedError: `[0].valueFrom.fieldRef.fieldPath: Unsupported value: "metadata.name[]": supported values: "metadata.annotations[]", "metadata.labels[]", "metadata.name", "metadata.namespace", "metadata.uid", "spec.nodeName", "spec.serviceAccountName", "status.hostIP", "status.podIP"`,
+		},
+		{
+			name: "metadata.labels without subscript",
 			envs: []core.EnvVar{{
 				Name: "labels",
 				ValueFrom: &core.EnvVarSource{
@@ -4105,10 +4150,10 @@ func TestValidateEnv(t *testing.T) {
 					},
 				},
 			}},
-			expectedError: `[0].valueFrom.fieldRef.fieldPath: Unsupported value: "metadata.labels": supported values: "metadata.name", "metadata.namespace", "metadata.uid", "spec.nodeName", "spec.serviceAccountName", "status.hostIP", "status.podIP"`,
+			expectedError: `[0].valueFrom.fieldRef.fieldPath: Unsupported value: "metadata.labels": supported values: "metadata.annotations[]", "metadata.labels[]", "metadata.name", "metadata.namespace", "metadata.uid", "spec.nodeName", "spec.serviceAccountName", "status.hostIP", "status.podIP"`,
 		},
 		{
-			name: "invalid fieldPath annotations",
+			name: "metadata.annotations without subscript",
 			envs: []core.EnvVar{{
 				Name: "abc",
 				ValueFrom: &core.EnvVarSource{
@@ -4118,7 +4163,7 @@ func TestValidateEnv(t *testing.T) {
 					},
 				},
 			}},
-			expectedError: `[0].valueFrom.fieldRef.fieldPath: Unsupported value: "metadata.annotations": supported values: "metadata.name", "metadata.namespace", "metadata.uid", "spec.nodeName", "spec.serviceAccountName", "status.hostIP", "status.podIP"`,
+			expectedError: `[0].valueFrom.fieldRef.fieldPath: Unsupported value: "metadata.annotations": supported values: "metadata.annotations[]", "metadata.labels[]", "metadata.name", "metadata.namespace", "metadata.uid", "spec.nodeName", "spec.serviceAccountName", "status.hostIP", "status.podIP"`,
 		},
 		{
 			name: "unsupported fieldPath",
@@ -4131,7 +4176,7 @@ func TestValidateEnv(t *testing.T) {
 					},
 				},
 			}},
-			expectedError: `valueFrom.fieldRef.fieldPath: Unsupported value: "status.phase": supported values: "metadata.name", "metadata.namespace", "metadata.uid", "spec.nodeName", "spec.serviceAccountName", "status.hostIP", "status.podIP"`,
+			expectedError: `valueFrom.fieldRef.fieldPath: Unsupported value: "status.phase": supported values: "metadata.annotations[]", "metadata.labels[]", "metadata.name", "metadata.namespace", "metadata.uid", "spec.nodeName", "spec.serviceAccountName", "status.hostIP", "status.podIP"`,
 		},
 	}
 	for _, tc := range errorCases {

pkg/fieldpath/fieldpath.go

@@ -42,7 +42,20 @@ func ExtractFieldPathAsString(obj interface{}, fieldPath string) (string, error)
 		return "", nil
 	}
 
-	switch fieldPath {
+	path, subscript := SplitMaybeSubscriptedPath(fieldPath)
+
+	if len(subscript) > 0 {
+		switch path {
+		case "metadata.annotations":
+			return accessor.GetAnnotations()[subscript], nil
+		case "metadata.labels":
+			return accessor.GetLabels()[subscript], nil
+		default:
+			return "", fmt.Errorf("fieldPath %q does not support subscript", fieldPath)
+		}
+	}
+
+	switch path {
 	case "metadata.annotations":
 		return FormatMap(accessor.GetAnnotations()), nil
 	case "metadata.labels":
@@ -57,3 +70,29 @@ func ExtractFieldPathAsString(obj interface{}, fieldPath string) (string, error)
 
 	return "", fmt.Errorf("unsupported fieldPath: %v", fieldPath)
 }
+
+// SplitMaybeSubscriptedPath checks whether the specified fieldPath is
+// subscripted, and
+//  - if yes, this function splits the fieldPath into path and subscript, and
+//    returns (path, subscript).
+//  - if no, this function returns (fieldPath, "").
+//
+// Example inputs and outputs:
+//  - "metadata.annotations['myKey']" --> ("metadata.annotations", "myKey")
+//  - "metadata.annotations['a[b]c']" --> ("metadata.annotations", "a[b]c")
+//  - "metadata.labels"               --> ("metadata.labels", "")
+//  - "metadata.labels['']"           --> ("metadata.labels", "")
+func SplitMaybeSubscriptedPath(fieldPath string) (string, string) {
+	if !strings.HasSuffix(fieldPath, "']") {
+		return fieldPath, ""
+	}
+	s := strings.TrimSuffix(fieldPath, "']")
+	parts := strings.SplitN(s, "['", 2)
+	if len(parts) < 2 {
+		return fieldPath, ""
+	}
+	if len(parts[0]) == 0 || len(parts[1]) == 0 {
+		return fieldPath, ""
+	}
+	return parts[0], parts[1]
+}

pkg/fieldpath/fieldpath_test.go

@@ -88,6 +88,16 @@ func TestExtractFieldPathAsString(t *testing.T) {
 			},
 			expectedValue: "builder=\"john-doe\"",
 		},
+		{
+			name:      "ok - annotation",
+			fieldPath: "metadata.annotations['spec.pod.beta.kubernetes.io/statefulset-index']",
+			obj: &v1.Pod{
+				ObjectMeta: metav1.ObjectMeta{
+					Annotations: map[string]string{"spec.pod.beta.kubernetes.io/statefulset-index": "1"},
+				},
+			},
+			expectedValue: "1",
+		},
 
 		{
 			name:      "invalid expression",
@@ -99,6 +109,16 @@ func TestExtractFieldPathAsString(t *testing.T) {
 			},
 			expectedMessageFragment: "unsupported fieldPath",
 		},
+		{
+			name:      "invalid annotation",
+			fieldPath: "metadata.annotations['unknown.key']",
+			obj: &v1.Pod{
+				ObjectMeta: metav1.ObjectMeta{
+					Annotations: map[string]string{"foo": "bar"},
+				},
+			},
+			expectedMessageFragment: "unsupported fieldPath",
+		},
 	}
 
 	for _, tc := range cases {
@@ -116,3 +136,79 @@ func TestExtractFieldPathAsString(t *testing.T) {
 		}
 	}
 }
+
+func TestSplitMaybeSubscriptedPath(t *testing.T) {
+	cases := []struct {
+		fieldPath         string
+		expectedPath      string
+		expectedSubscript string
+	}{
+		{
+			fieldPath:         "metadata.annotations['key']",
+			expectedPath:      "metadata.annotations",
+			expectedSubscript: "key",
+		},
+		{
+			fieldPath:         "metadata.annotations['a[b']c']",
+			expectedPath:      "metadata.annotations",
+			expectedSubscript: "a[b']c",
+		},
+		{
+			fieldPath:         "metadata.labels['['key']",
+			expectedPath:      "metadata.labels",
+			expectedSubscript: "['key",
+		},
+		{
+			fieldPath:         "metadata.labels['key']']",
+			expectedPath:      "metadata.labels",
+			expectedSubscript: "key']",
+		},
+		{
+			fieldPath:         "metadata.labels[ 'key' ]",
+			expectedPath:      "metadata.labels[ 'key' ]",
+			expectedSubscript: "",
+		},
+		{
+			fieldPath:         "metadata.labels['']",
+			expectedPath:      "metadata.labels['']",
+			expectedSubscript: "",
+		},
+		{
+			fieldPath:         "metadata.labels[' ']",
+			expectedPath:      "metadata.labels",
+			expectedSubscript: " ",
+		},
+		{
+			fieldPath:         "metadata.labels[]",
+			expectedPath:      "metadata.labels[]",
+			expectedSubscript: "",
+		},
+		{
+			fieldPath:         "metadata.labels[']",
+			expectedPath:      "metadata.labels[']",
+			expectedSubscript: "",
+		},
+		{
+			fieldPath:         "metadata.labels['key']foo",
+			expectedPath:      "metadata.labels['key']foo",
+			expectedSubscript: "",
+		},
+		{
+			fieldPath:         "['key']",
+			expectedPath:      "['key']",
+			expectedSubscript: "",
+		},
+		{
+			fieldPath:         "metadata.labels",
+			expectedPath:      "metadata.labels",
+			expectedSubscript: "",
+		},
+	}
+	for _, tc := range cases {
+		path, subscript := SplitMaybeSubscriptedPath(tc.fieldPath)
+		if path != tc.expectedPath || subscript != tc.expectedSubscript {
+			t.Errorf("SplitMaybeSubscriptedPath(%q) = (%q, %q), expect (%q, %q)",
+				tc.fieldPath, path, subscript, tc.expectedPath, tc.expectedSubscript)
+		}
+	}
+}

pkg/volume/projected/projected_test.go

@@ -544,6 +544,48 @@ func TestCollectDataWithDownwardAPI(t *testing.T) {
 		payload    map[string]util.FileProjection
 		success    bool
 	}{
+		{
+			name: "annotation",
+			volumeFile: []v1.DownwardAPIVolumeFile{
+				{Path: "annotation", FieldRef: &v1.ObjectFieldSelector{
+					FieldPath: "metadata.annotations['a1']"}}},
+			pod: &v1.Pod{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      testPodName,
+					Namespace: testNamespace,
+					Annotations: map[string]string{
+						"a1": "value1",
+						"a2": "value2",
+					},
+					UID: testPodUID},
+			},
+			mode: 0644,
+			payload: map[string]util.FileProjection{
+				"annotation": {Data: []byte("value1"), Mode: 0644},
+			},
+			success: true,
+		},
+		{
+			name: "annotation-error",
+			volumeFile: []v1.DownwardAPIVolumeFile{
+				{Path: "annotation", FieldRef: &v1.ObjectFieldSelector{
+					FieldPath: "metadata.annotations['']"}}},
+			pod: &v1.Pod{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      testPodName,
+					Namespace: testNamespace,
+					Annotations: map[string]string{
+						"a1": "value1",
+						"a2": "value2",
+					},
+					UID: testPodUID},
+			},
+			mode: 0644,
+			payload: map[string]util.FileProjection{
+				"annotation": {Data: []byte("does-not-matter-because-this-test-case-will-fail-anyway"), Mode: 0644},
+			},
+			success: false,
+		},
 		{
 			name: "labels",
 			volumeFile: []v1.DownwardAPIVolumeFile{