Merge pull request #6739 from pmorie/downward-api

Env var sources / downward API

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"
@@ -702,7 +703,7 @@ 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
 	}
@@ -780,7 +781,7 @@ 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
@@ -791,7 +792,7 @@ 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
 	}
@@ -803,7 +804,13 @@ 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.
@@ -813,6 +820,33 @@ 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)
 		}