Add downward API for environment vars

pkg/api/testing/fuzzer.go

@@ -188,6 +188,20 @@ func FuzzerFor(t *testing.T, version string, src rand.Source) *fuzz.Fuzzer {
 			c.FuzzNoCustom(ct)                                          // fuzz self without calling this function again
 			ct.TerminationMessagePath = "/" + ct.TerminationMessagePath // Must be non-empty
 		},
+		func(ev *api.EnvVar, c fuzz.Continue) {
+			ev.Name = c.RandString()
+			if c.RandBool() {
+				ev.Value = c.RandString()
+			} else {
+				ev.ValueFrom = &api.EnvVarSource{}
+				ev.ValueFrom.FieldPath = &api.ObjectFieldSelector{}
+
+				versions := []string{"v1beta1", "v1beta2", "v1beta3"}
+
+				ev.ValueFrom.FieldPath.APIVersion = versions[c.Rand.Intn(len(versions))]
+				ev.ValueFrom.FieldPath.FieldPath = c.RandString()
+			}
+		},
 		func(e *api.Event, c fuzz.Continue) {
 			c.FuzzNoCustom(e) // fuzz self without calling this function again
 			// Fix event count to 1, otherwise, if a v1beta1 or v1beta2 event has a count set arbitrarily, it's count is ignored

pkg/api/types.go

@@ -508,6 +508,25 @@ type EnvVar struct {
 	Name string `json:"name"`
 	// Optional: defaults to "".
 	Value string `json:"value,omitempty"`
+	// Optional: specify a source the value of this var should come from.
+	ValueFrom *EnvVarSource `json:"valueFrom,omitempty"`
+}
+
+// EnvVarSource represents a source for the value of an EnvVar.
+// Only one of its members may be specified.
+type EnvVarSource struct {
+	// Selects a field of the pod; only name and namespace are supported.
+	FieldPath *ObjectFieldSelector `json:"fieldPath,omitempty"`
+}
+
+// ObjectFieldSelector selects an APIVersioned field of an object.
+type ObjectFieldSelector struct {
+	// The API version the FieldPath is written in terms of.
+	// If no value is specified, it will be defaulted from the APIVersion
+	// the enclosing object is created with.
+	APIVersion string `json:"apiVersion,omitempty"`
+	// The path of the field to select in the specified API version
+	FieldPath string `json:"fieldPath,omitempty"`
 }
 
 // HTTPGetAction describes an action based on HTTP Get requests.

pkg/api/v1beta1/conversion.go

@@ -116,6 +116,11 @@ func init() {
 			out.Value = in.Value
 			out.Key = in.Name
 			out.Name = in.Name
+
+			if err := s.Convert(&in.ValueFrom, &out.ValueFrom, 0); err != nil {
+				return err
+			}
+
 			return nil
 		},
 		func(in *EnvVar, out *newer.EnvVar, s conversion.Scope) error {
@@ -125,9 +130,13 @@ func init() {
 			} else {
 				out.Name = in.Key
 			}
+
+			if err := s.Convert(&in.ValueFrom, &out.ValueFrom, 0); err != nil {
+				return err
+			}
+
 			return nil
 		},
-
 		// Path & MountType are deprecated.
 		func(in *newer.VolumeMount, out *VolumeMount, s conversion.Scope) error {
 			out.Name = in.Name

pkg/api/v1beta1/defaults.go

@@ -166,6 +166,11 @@ func init() {
 				obj.ExternalID = obj.ID
 			}
 		},
+		func(obj *ObjectFieldSelector) {
+			if obj.APIVersion == "" {
+				obj.APIVersion = "v1beta1"
+			}
+		},
 	)
 }
 

pkg/api/v1beta1/defaults_test.go

@@ -294,3 +294,29 @@ func TestSetDefaultMinionExternalID(t *testing.T) {
 		t.Errorf("Expected default External ID: %s, got: %s", name, m2.ExternalID)
 	}
 }
+
+func TestSetDefaultObjectFieldSelectorAPIVersion(t *testing.T) {
+	s := current.ContainerManifest{
+		Containers: []current.Container{
+			{
+				Env: []current.EnvVar{
+					{
+						ValueFrom: &current.EnvVarSource{
+							FieldPath: &current.ObjectFieldSelector{},
+						},
+					},
+				},
+			},
+		},
+	}
+	obj2 := roundTrip(t, runtime.Object(&current.ContainerManifestList{
+		Items: []current.ContainerManifest{s},
+	}))
+	sList2 := obj2.(*current.ContainerManifestList)
+	s2 := sList2.Items[0]
+
+	apiVersion := s2.Containers[0].Env[0].ValueFrom.FieldPath.APIVersion
+	if apiVersion != "v1beta1" {
+		t.Errorf("Expected default APIVersion v1beta1, got: %v", apiVersion)
+	}
+}

pkg/api/v1beta1/types.go

@@ -397,6 +397,23 @@ type EnvVar struct {
 	Key  string `json:"key,omitempty" description:"name of the environment variable; must be a C_IDENTIFIER; deprecated - use name instead"`
 	// Optional: defaults to "".
 	Value string `json:"value,omitempty" description:"value of the environment variable; defaults to empty string"`
+	// Optional: specify a source the value of this var should come from.
+	ValueFrom *EnvVarSource `json:"valueFrom,omitempty" description:"source for the environment variable's value; cannot be used if value is not empty"`
+}
+
+// EnvVarSource represents a source for the value of an EnvVar.
+// Only one of its members may be specified.
+type EnvVarSource struct {
+	// Selects a field of the pod; only name and namespace are supported.
+	FieldPath *ObjectFieldSelector `json:"fieldPath,omitempty" description:"selects a field of the pod; only name and namespace are supported"`
+}
+
+// ObjectFieldSelector selects an APIVersioned field of an object.
+type ObjectFieldSelector struct {
+	// The API version the FieldPath is written in terms of.
+	APIVersion string `json:"apiVersion,omitempty" description="The API version that FieldPath is written in terms of"`
+	// The path of the field to select in the specified API version
+	FieldPath string `json:"fieldPath,omitempty" description="The path of the field to select in the specified API version"`
 }
 
 // HTTPGetAction describes an action based on HTTP Get requests.

pkg/api/v1beta2/defaults.go

@@ -167,6 +167,11 @@ func init() {
 				obj.ExternalID = obj.ID
 			}
 		},
+		func(obj *ObjectFieldSelector) {
+			if obj.APIVersion == "" {
+				obj.APIVersion = "v1beta2"
+			}
+		},
 	)
 }
 

pkg/api/v1beta2/defaults_test.go

@@ -293,3 +293,29 @@ func TestSetDefaultMinionExternalID(t *testing.T) {
 		t.Errorf("Expected default External ID: %s, got: %s", name, m2.ExternalID)
 	}
 }
+
+func TestSetDefaultObjectFieldSelectorAPIVersion(t *testing.T) {
+	s := current.ContainerManifest{
+		Containers: []current.Container{
+			{
+				Env: []current.EnvVar{
+					{
+						ValueFrom: &current.EnvVarSource{
+							FieldPath: &current.ObjectFieldSelector{},
+						},
+					},
+				},
+			},
+		},
+	}
+	obj2 := roundTrip(t, runtime.Object(&current.ContainerManifestList{
+		Items: []current.ContainerManifest{s},
+	}))
+	sList2 := obj2.(*current.ContainerManifestList)
+	s2 := sList2.Items[0]
+
+	apiVersion := s2.Containers[0].Env[0].ValueFrom.FieldPath.APIVersion
+	if apiVersion != "v1beta2" {
+		t.Errorf("Expected default APIVersion v1beta2, got: %v", apiVersion)
+	}
+}

pkg/api/v1beta2/types.go

@@ -381,6 +381,23 @@ type EnvVar struct {
 	Name string `json:"name" description:"name of the environment variable; must be a C_IDENTIFIER"`
 	// Optional: defaults to "".
 	Value string `json:"value,omitempty" description:"value of the environment variable; defaults to empty string"`
+	// Optional: specify a source the value of this var should come from.
+	ValueFrom *EnvVarSource `json:"valueFrom,omitempty" description:"source for the environment variable's value; cannot be used if value is not empty"`
+}
+
+// EnvVarSource represents a source for the value of an EnvVar.
+// Only one of its members may be specified.
+type EnvVarSource struct {
+	// Selects a field of the pod; only name and namespace are supported.
+	FieldPath *ObjectFieldSelector `json:"fieldPath,omitempty" description:"selects a field of the pod; only name and namespace are supported"`
+}
+
+// ObjectFieldSelector selects an APIVersioned field of an object.
+type ObjectFieldSelector struct {
+	// The API version the FieldPath is written in terms of.
+	APIVersion string `json:"apiVersion,omitempty" description="The API version that FieldPath is written in terms of"`
+	// The path of the field to select in the specified API version
+	FieldPath string `json:"fieldPath,omitempty" description="The path of the field to select in the specified API version"`
 }
 
 // HTTPGetAction describes an action based on HTTP Get requests.

pkg/api/v1beta3/conversion.go

@@ -1794,6 +1794,23 @@ func init() {
 			out.Path = in.Path
 			return nil
 		},
+		func(in *EnvVar, out *newer.EnvVar, s conversion.Scope) error {
+			out.Name = in.Name
+			out.Value = in.Value
+			if err := s.Convert(&in.ValueFrom, &out.ValueFrom, 0); err != nil {
+				return err
+			}
+
+			return nil
+		},
+		func(in *newer.EnvVar, out *EnvVar, s conversion.Scope) error {
+			out.Name = in.Name
+			out.Value = in.Value
+			if err := s.Convert(&in.ValueFrom, &out.ValueFrom, 0); err != nil {
+				return err
+			}
+			return nil
+		},
 		func(in *PodSpec, out *newer.PodSpec, s conversion.Scope) error {
 			if in.Volumes != nil {
 				out.Volumes = make([]newer.Volume, len(in.Volumes))
@@ -2715,6 +2732,7 @@ func init() {
 		func(label, value string) (string, string, error) {
 			switch label {
 			case "metadata.name",
+				"metadata.namespace",
 				"status.phase",
 				"spec.host":
 				return label, value, nil

pkg/api/v1beta3/defaults.go

@@ -128,6 +128,11 @@ func init() {
 				obj.Spec.ExternalID = obj.Name
 			}
 		},
+		func(obj *ObjectFieldSelector) {
+			if obj.APIVersion == "" {
+				obj.APIVersion = "v1beta3"
+			}
+		},
 	)
 }
 

pkg/api/v1beta3/defaults_test.go

@@ -302,3 +302,30 @@ func TestSetDefaultNodeExternalID(t *testing.T) {
 		t.Errorf("Expected default External ID: %s, got: %s", name, n2.Spec.ExternalID)
 	}
 }
+
+func TestSetDefaultObjectFieldSelectorAPIVersion(t *testing.T) {
+	s := current.PodSpec{
+		Containers: []current.Container{
+			{
+				Env: []current.EnvVar{
+					{
+						ValueFrom: &current.EnvVarSource{
+							FieldPath: &current.ObjectFieldSelector{},
+						},
+					},
+				},
+			},
+		},
+	}
+	pod := &current.Pod{
+		Spec: s,
+	}
+	obj2 := roundTrip(t, runtime.Object(pod))
+	pod2 := obj2.(*current.Pod)
+	s2 := pod2.Spec
+
+	apiVersion := s2.Containers[0].Env[0].ValueFrom.FieldPath.APIVersion
+	if apiVersion != "v1beta3" {
+		t.Errorf("Expected default APIVersion v1beta3, got: %v", apiVersion)
+	}
+}

pkg/api/v1beta3/types.go

@@ -519,6 +519,23 @@ type EnvVar struct {
 	Name string `json:"name" description:"name of the environment variable; must be a C_IDENTIFIER"`
 	// Optional: defaults to "".
 	Value string `json:"value,omitempty" description:"value of the environment variable; defaults to empty string"`
+	// Optional: specify a source the value of this var should come from.
+	ValueFrom *EnvVarSource `json:"valueFrom,omitempty" description:"source for the environment variable's value; cannot be used if value is not empty"`
+}
+
+// EnvVarSource represents a source for the value of an EnvVar.
+// Only one of its members may be specified.
+type EnvVarSource struct {
+	// Selects a field of the pod; only name and namespace are supported.
+	FieldPath *ObjectFieldSelector `json:"fieldPath,omitempty" description:"selects a field of the pod; only name and namespace are supported"`
+}
+
+// ObjectFieldSelector selects an APIVersioned field of an object.
+type ObjectFieldSelector struct {
+	// The API version the FieldPath is written in terms of.
+	APIVersion string `json:"apiVersion,omitempty" description="The API version that FieldPath is written in terms of"`
+	// The path of the field to select in the specified API version
+	FieldPath string `json:"fieldPath,omitempty" description="The path of the field to select in the specified API version"`
 }
 
 // HTTPGetAction describes an action based on HTTP Get requests.

pkg/api/validation/validation.go

@@ -555,15 +555,58 @@ func validateEnv(vars []api.EnvVar) errs.ValidationErrorList {
 		vErrs := errs.ValidationErrorList{}
 		if len(ev.Name) == 0 {
 			vErrs = append(vErrs, errs.NewFieldRequired("name"))
-		}
+		} else if !util.IsCIdentifier(ev.Name) {
-		if !util.IsCIdentifier(ev.Name) {
 			vErrs = append(vErrs, errs.NewFieldInvalid("name", ev.Name, cIdentifierErrorMsg))
 		}
+		vErrs = append(vErrs, validateEnvVarValueFrom(ev).Prefix("valueFrom")...)
 		allErrs = append(allErrs, vErrs.PrefixIndex(i)...)
 	}
 	return allErrs
 }
 
+func validateEnvVarValueFrom(ev api.EnvVar) errs.ValidationErrorList {
+	allErrs := errs.ValidationErrorList{}
+
+	if ev.ValueFrom == nil {
+		return allErrs
+	}
+
+	numSources := 0
+
+	switch {
+	case ev.ValueFrom.FieldPath != nil:
+		numSources++
+		allErrs = append(allErrs, validateObjectFieldSelector(ev.ValueFrom.FieldPath).Prefix("fieldPath")...)
+	}
+
+	if ev.Value != "" && numSources != 0 {
+		allErrs = append(allErrs, errs.NewFieldInvalid("", "", "sources cannot be specified when value is not empty"))
+	}
+
+	return allErrs
+}
+
+var validFieldPathExpressions = util.NewStringSet("metadata.name", "metadata.namespace")
+
+func validateObjectFieldSelector(fs *api.ObjectFieldSelector) errs.ValidationErrorList {
+	allErrs := errs.ValidationErrorList{}
+
+	if fs.APIVersion == "" {
+		allErrs = append(allErrs, errs.NewFieldRequired("apiVersion"))
+	} else if fs.FieldPath == "" {
+		allErrs = append(allErrs, errs.NewFieldRequired("fieldPath"))
+	} else {
+		internalFieldPath, _, err := api.Scheme.ConvertFieldLabel(fs.APIVersion, "Pod", fs.FieldPath, "")
+		if err != nil {
+			allErrs = append(allErrs, errs.NewFieldInvalid("fieldPath", fs.FieldPath, "error converting fieldPath"))
+		} else if !validFieldPathExpressions.Has(internalFieldPath) {
+			allErrs = append(allErrs, errs.NewFieldNotSupported("fieldPath", internalFieldPath))
+		}
+	}
+
+	return allErrs
+}
+
 func validateVolumeMounts(mounts []api.VolumeMount, volumes util.StringSet) errs.ValidationErrorList {
 	allErrs := errs.ValidationErrorList{}
 

pkg/api/validation/validation_test.go

@@ -633,23 +633,108 @@ func TestValidateEnv(t *testing.T) {
 		{Name: "ABC", Value: "value"},
 		{Name: "AbC_123", Value: "value"},
 		{Name: "abc", Value: ""},
+		{
+			Name: "abc",
+			ValueFrom: &api.EnvVarSource{
+				FieldPath: &api.ObjectFieldSelector{
+					APIVersion: "v1beta3",
+					FieldPath:  "metadata.name",
+				},
+			},
+		},
 	}
 	if errs := validateEnv(successCase); len(errs) != 0 {
 		t.Errorf("expected success: %v", errs)
 	}
 
-	errorCases := map[string][]api.EnvVar{
+	errorCases := []struct {
-		"zero-length name":        {{Name: ""}},
+		name          string
-		"name not a C identifier": {{Name: "a.b.c"}},
+		envs          []api.EnvVar
+		expectedError string
+	}{
+		{
+			name:          "zero-length name",
+			envs:          []api.EnvVar{{Name: ""}},
+			expectedError: "[0].name: required value",
+		},
+		{
+			name:          "name not a C identifier",
+			envs:          []api.EnvVar{{Name: "a.b.c"}},
+			expectedError: "[0].name: invalid value 'a.b.c': must match regex [A-Za-z_][A-Za-z0-9_]*",
+		},
+		{
+			name: "value and valueFrom specified",
+			envs: []api.EnvVar{{
+				Name:  "abc",
+				Value: "foo",
+				ValueFrom: &api.EnvVarSource{
+					FieldPath: &api.ObjectFieldSelector{
+						APIVersion: "v1beta3",
+						FieldPath:  "metadata.name",
+					},
+				},
+			}},
+			expectedError: "[0].valueFrom: invalid value '': sources cannot be specified when value is not empty",
+		},
+		{
+			name: "missing FieldPath on ObjectFieldSelector",
+			envs: []api.EnvVar{{
+				Name: "abc",
+				ValueFrom: &api.EnvVarSource{
+					FieldPath: &api.ObjectFieldSelector{
+						APIVersion: "v1beta3",
+					},
+				},
+			}},
+			expectedError: "[0].valueFrom.fieldPath.fieldPath: required value",
+		},
+		{
+			name: "missing APIVersion on ObjectFieldSelector",
+			envs: []api.EnvVar{{
+				Name: "abc",
+				ValueFrom: &api.EnvVarSource{
+					FieldPath: &api.ObjectFieldSelector{
+						FieldPath: "metadata.name",
+					},
+				},
+			}},
+			expectedError: "[0].valueFrom.fieldPath.apiVersion: required value",
+		},
+		{
+			name: "invalid fieldPath",
+			envs: []api.EnvVar{{
+				Name: "abc",
+				ValueFrom: &api.EnvVarSource{
+					FieldPath: &api.ObjectFieldSelector{
+						FieldPath:  "metadata.whoops",
+						APIVersion: "v1beta3",
+					},
+				},
+			}},
+			expectedError: "[0].valueFrom.fieldPath.fieldPath: invalid value 'metadata.whoops': error converting fieldPath",
+		},
+		{
+			name: "unsupported fieldPath",
+			envs: []api.EnvVar{{
+				Name: "abc",
+				ValueFrom: &api.EnvVarSource{
+					FieldPath: &api.ObjectFieldSelector{
+						FieldPath:  "status.phase",
+						APIVersion: "v1beta3",
+					},
+				},
+			}},
+			expectedError: "[0].valueFrom.fieldPath.fieldPath: unsupported value 'status.phase'",
+		},
 	}
-	for k, v := range errorCases {
+	for _, tc := range errorCases {
-		if errs := validateEnv(v); len(errs) == 0 {
+		if errs := validateEnv(tc.envs); len(errs) == 0 {
-			t.Errorf("expected failure for %s", k)
+			t.Errorf("expected failure for %s", tc.name)
 		} else {
 			for i := range errs {
-				detail := errs[i].(*errors.ValidationError).Detail
+				str := errs[i].(*errors.ValidationError).Error()
-				if detail != "" && detail != cIdentifierErrorMsg {
+				if str != "" && str != tc.expectedError {
-					t.Errorf("%s: expected error detail either empty or %s, got %s", k, cIdentifierErrorMsg, detail)
+					t.Errorf("%s: expected error detail either empty or %s, got %s", tc.name, tc.expectedError, str)
 				}
 			}
 		}

pkg/fieldpath/doc.go

@@ -0,0 +1,19 @@
+/*
+Copyright 2015 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package fieldpath supplies methods for extracting fields from objects
+// given a path to a field.
+package fieldpath

pkg/fieldpath/fieldpath.go

@@ -0,0 +1,47 @@
+/*
+Copyright 2015 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package fieldpath
+
+import (
+	"fmt"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/api/meta"
+)
+
+// ExtractFieldPathAsString extracts the field from the given object
+// and returns it as a string.  The object must be a pointer to an
+// API type.
+//
+// Currently, this API is limited to supporting the fieldpaths:
+//
+// 1.  metadata.name - The name of an API object
+// 2.  metadata.namespace - The namespace of an API object
+func ExtractFieldPathAsString(obj interface{}, fieldPath string) (string, error) {
+	accessor, err := meta.Accessor(obj)
+	if err != nil {
+		return "", nil
+	}
+
+	switch fieldPath {
+	case "metadata.name":
+		return accessor.Name(), nil
+	case "metadata.namespace":
+		return accessor.Namespace(), nil
+	}
+
+	return "", fmt.Errorf("Unsupported fieldPath: %v", fieldPath)
+}

pkg/fieldpath/fieldpath_test.go

@@ -0,0 +1,86 @@
+/*
+Copyright 2015 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package fieldpath
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
+)
+
+func TestExtractFieldPathAsString(t *testing.T) {
+	cases := []struct {
+		name                    string
+		fieldPath               string
+		obj                     interface{}
+		expectedValue           string
+		expectedMessageFragment string
+	}{
+		{
+			name:      "not an API object",
+			fieldPath: "metadata.name",
+			obj:       "",
+			expectedMessageFragment: "expected struct",
+		},
+		{
+			name:      "ok - namespace",
+			fieldPath: "metadata.namespace",
+			obj: &api.Pod{
+				ObjectMeta: api.ObjectMeta{
+					Namespace: "object-namespace",
+				},
+			},
+			expectedValue: "object-namespace",
+		},
+		{
+			name:      "ok - name",
+			fieldPath: "metadata.name",
+			obj: &api.Pod{
+				ObjectMeta: api.ObjectMeta{
+					Name: "object-name",
+				},
+			},
+			expectedValue: "object-name",
+		},
+		{
+			name:      "invalid expression",
+			fieldPath: "metadata.whoops",
+			obj: &api.Pod{
+				ObjectMeta: api.ObjectMeta{
+					Namespace: "object-namespace",
+				},
+			},
+			expectedMessageFragment: "Unsupported fieldPath",
+		},
+	}
+
+	for _, tc := range cases {
+		actual, err := ExtractFieldPathAsString(tc.obj, tc.fieldPath)
+		if err != nil {
+			if tc.expectedMessageFragment != "" {
+				if !strings.Contains(err.Error(), tc.expectedMessageFragment) {
+					t.Errorf("%v: Unexpected error message: %q, expected to contain %q", tc.name, err, tc.expectedMessageFragment)
+				}
+			} else {
+				t.Errorf("%v: unexpected error: %v", tc.name, err)
+			}
+		} else if e := tc.expectedValue; e != "" && e != actual {
+			t.Errorf("%v: Unexpected result; got %q, expected %q", tc.name, actual, e)
+		}
+	}
+}

pkg/kubelet/kubelet.go

@@ -36,6 +36,7 @@ import (
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/client/cache"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/client/record"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/cloudprovider"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/fieldpath"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/fields"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/kubelet/cadvisor"
 	kubecontainer "github.com/GoogleCloudPlatform/kubernetes/pkg/kubelet/container"
@@ -706,7 +707,7 @@ func (kl *Kubelet) GenerateRunContainerOptions(pod *api.Pod, container *api.Cont
 		return nil, fmt.Errorf("impossible: cannot find the mounted volumes for pod %q", kubecontainer.GetPodFullName(pod))
 	}
 	opts.Binds = makeBinds(container, vol)
-	opts.Envs, err = kl.makeEnvironmentVariables(pod.Namespace, container)
+	opts.Envs, err = kl.makeEnvironmentVariables(pod, container)
 	if err != nil {
 		return nil, err
 	}
@@ -784,7 +785,7 @@ func (kl *Kubelet) getServiceEnvVarMap(ns string) (map[string]string, error) {
 }
 
 // Make the service environment variables for a pod in the given namespace.
-func (kl *Kubelet) makeEnvironmentVariables(ns string, container *api.Container) ([]string, error) {
+func (kl *Kubelet) makeEnvironmentVariables(pod *api.Pod, container *api.Container) ([]string, error) {
 	var result []string
 	// Note:  These are added to the docker.Config, but are not included in the checksum computed
 	// by dockertools.BuildDockerName(...).  That way, we can still determine whether an
@@ -795,7 +796,7 @@ func (kl *Kubelet) makeEnvironmentVariables(ns string, container *api.Container)
 	// To avoid this users can: (1) wait between starting a service and starting; or (2) detect
 	// missing service env var and exit and be restarted; or (3) use DNS instead of env vars
 	// and keep trying to resolve the DNS name of the service (recommended).
-	serviceEnv, err := kl.getServiceEnvVarMap(ns)
+	serviceEnv, err := kl.getServiceEnvVarMap(pod.Namespace)
 	if err != nil {
 		return result, err
 	}
@@ -807,7 +808,13 @@ func (kl *Kubelet) makeEnvironmentVariables(ns string, container *api.Container)
 		// env vars.
 		// TODO: remove this net line once all platforms use apiserver+Pods.
 		delete(serviceEnv, value.Name)
-		result = append(result, fmt.Sprintf("%s=%s", value.Name, value.Value))
+
+		runtimeValue, err := kl.runtimeEnvVarValue(value, pod)
+		if err != nil {
+			return result, err
+		}
+
+		result = append(result, fmt.Sprintf("%s=%s", value.Name, runtimeValue))
 	}
 
 	// Append remaining service env vars.
@@ -817,6 +824,33 @@ func (kl *Kubelet) makeEnvironmentVariables(ns string, container *api.Container)
 	return result, nil
 }
 
+// runtimeEnvVarValue determines the value that an env var should take when a container
+// is started.  If the value of the env var is the empty string, the source of the env var
+// is resolved, if one is specified.
+//
+// TODO: preliminary factoring; make better
+func (kl *Kubelet) runtimeEnvVarValue(envVar api.EnvVar, pod *api.Pod) (string, error) {
+	runtimeVal := envVar.Value
+	if runtimeVal != "" {
+		return runtimeVal, nil
+	}
+
+	if envVar.ValueFrom != nil && envVar.ValueFrom.FieldPath != nil {
+		return kl.podFieldSelectorRuntimeValue(envVar.ValueFrom.FieldPath, pod)
+	}
+
+	return runtimeVal, nil
+}
+
+func (kl *Kubelet) podFieldSelectorRuntimeValue(fs *api.ObjectFieldSelector, pod *api.Pod) (string, error) {
+	internalFieldPath, _, err := api.Scheme.ConvertFieldLabel(fs.APIVersion, "Pod", fs.FieldPath, "")
+	if err != nil {
+		return "", err
+	}
+
+	return fieldpath.ExtractFieldPathAsString(pod, internalFieldPath)
+}
+
 // getClusterDNS returns a list of the DNS servers and a list of the DNS search
 // domains of the cluster.
 func (kl *Kubelet) getClusterDNS(pod *api.Pod) ([]string, []string, error) {

pkg/kubelet/kubelet_test.go

@@ -68,6 +68,8 @@ type TestKubelet struct {
 	fakeMirrorClient *fakeMirrorClient
 }
 
+const testKubeletHostname = "testnode"
+
 func newTestKubelet(t *testing.T) *TestKubelet {
 	fakeDocker := &dockertools.FakeDockerClient{Errors: make(map[string]error), RemovedImages: util.StringSet{}}
 	fakeRecorder := &record.FakeRecorder{}
@@ -2378,6 +2380,39 @@ func TestMakeEnvironmentVariables(t *testing.T) {
 				"KUBERNETES_RO_PORT_8087_TCP_ADDR=1.2.3.7"),
 			21,
 		},
+		{
+			"downward api pod",
+			"downward-api",
+			&api.Container{
+				Env: []api.EnvVar{
+					{
+						Name: "POD_NAME",
+						ValueFrom: &api.EnvVarSource{
+							FieldPath: &api.ObjectFieldSelector{
+								APIVersion: "v1beta3",
+								FieldPath:  "metadata.name",
+							},
+						},
+					},
+					{
+						Name: "POD_NAMESPACE",
+						ValueFrom: &api.EnvVarSource{
+							FieldPath: &api.ObjectFieldSelector{
+								APIVersion: "v1beta3",
+								FieldPath:  "metadata.namespace",
+							},
+						},
+					},
+				},
+			},
+			"nothing",
+			true,
+			util.NewStringSet(
+				"POD_NAME=dapi-test-pod-name",
+				"POD_NAMESPACE=downward-api",
+			),
+			2,
+		},
 	}
 
 	for _, tc := range testCases {
@@ -2390,7 +2425,14 @@ func TestMakeEnvironmentVariables(t *testing.T) {
 			kl.serviceLister = testServiceLister{services}
 		}
 
-		result, err := kl.makeEnvironmentVariables(tc.ns, tc.container)
+		testPod := &api.Pod{
+			ObjectMeta: api.ObjectMeta{
+				Namespace: tc.ns,
+				Name:      "dapi-test-pod-name",
+			},
+		}
+
+		result, err := kl.makeEnvironmentVariables(testPod, tc.container)
 		if err != nil {
 			t.Errorf("[%v] Unexpected error: %v", tc.name, err)
 		}

test/e2e/downward_api.go

@@ -0,0 +1,96 @@
+/*
+Copyright 2015 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package e2e
+
+import (
+	"fmt"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/util"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Downward API", func() {
+	var c *client.Client
+	var ns string
+
+	BeforeEach(func() {
+		var err error
+		c, err = loadClient()
+		Expect(err).NotTo(HaveOccurred())
+		ns_, err := createTestingNS("downward-api", c)
+		ns = ns_.Name
+		Expect(err).NotTo(HaveOccurred())
+	})
+
+	AfterEach(func() {
+		// Clean up the namespace if a non-default one was used
+		if ns != api.NamespaceDefault {
+			By("Cleaning up the namespace")
+			err := c.Namespaces().Delete(ns)
+			expectNoError(err)
+		}
+	})
+
+	It("should provide pod name and namespace as env vars", func() {
+		podName := "downward-api-" + string(util.NewUUID())
+		pod := &api.Pod{
+			ObjectMeta: api.ObjectMeta{
+				Name:   podName,
+				Labels: map[string]string{"name": podName},
+			},
+			Spec: api.PodSpec{
+				Containers: []api.Container{
+					{
+						Name:    "dapi-container",
+						Image:   "gcr.io/google_containers/busybox",
+						Command: []string{"sh", "-c", "env"},
+						Env: []api.EnvVar{
+							{
+								Name: "POD_NAME",
+								ValueFrom: &api.EnvVarSource{
+									FieldPath: &api.ObjectFieldSelector{
+										APIVersion: "v1beta3",
+										FieldPath:  "metadata.name",
+									},
+								},
+							},
+							{
+								Name: "POD_NAMESPACE",
+								ValueFrom: &api.EnvVarSource{
+									FieldPath: &api.ObjectFieldSelector{
+										APIVersion: "v1beta3",
+										FieldPath:  "metadata.namespace",
+									},
+								},
+							},
+						},
+					},
+				},
+				RestartPolicy: api.RestartPolicyNever,
+			},
+		}
+
+		testContainerOutputInNamespace("downward api env vars", c, pod, []string{
+			fmt.Sprintf("POD_NAME=%v", podName),
+			fmt.Sprintf("POD_NAMESPACE=%v", ns),
+		}, ns)
+	})
+})