Refactor env.go

This copies and pastes the loop that used to exist in

func populateEnvironmentVariables(..) {
	...
	for _, env := range container.Env {
		... <--- This code
	}
}

Into getEnvironmentVariableValue. getEnvironmentVariableValue
returns val, err, where val is a pointer to a string
to indicate optionality.

go.mod

@@ -27,6 +27,7 @@ require (
 	k8s.io/klog v1.0.0
 	k8s.io/klog/v2 v2.0.0
 	k8s.io/kubernetes v1.18.4
+	k8s.io/utils v0.0.0-20200603063816-c1c6865ac451
 	sigs.k8s.io/controller-runtime v0.6.3
 )
 

internal/podutils/env.go

@@ -20,6 +20,8 @@ import (
 	"sort"
 	"strings"
 
+	"github.com/virtual-kubelet/virtual-kubelet/internal/manager"
+	"github.com/virtual-kubelet/virtual-kubelet/log"
 	corev1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -31,9 +33,7 @@ import (
 	fieldpath "k8s.io/kubernetes/pkg/fieldpath"
 	"k8s.io/kubernetes/pkg/kubelet/envvars"
 	"k8s.io/kubernetes/third_party/forked/golang/expansion"
-
+	"k8s.io/utils/pointer"
-	"github.com/virtual-kubelet/virtual-kubelet/internal/manager"
-	"github.com/virtual-kubelet/virtual-kubelet/log"
 )
 
 const (
@@ -292,7 +292,6 @@ loop:
 
 // makeEnvironmentMap returns a map representing the resolved environment of the specified container after being populated from the entries in the ".env" and ".envFrom" field.
 func makeEnvironmentMap(ctx context.Context, pod *corev1.Pod, container *corev1.Container, rm *manager.ResourceManager, recorder record.EventRecorder, res map[string]string) error {
-
 	// TODO If pod.Spec.EnableServiceLinks is nil then fail as per 1.14 kubelet.
 	enableServiceLinks := corev1.DefaultEnableServiceLinks
 	if pod.Spec.EnableServiceLinks != nil {
@@ -314,14 +313,32 @@ func makeEnvironmentMap(ctx context.Context, pod *corev1.Pod, container *corev1.
 	mappingFunc := expansion.MappingFuncFor(res, svcEnv)
 
 	// Iterate over environment variables in order to populate the map.
-loop:
 	for _, env := range container.Env {
+		val, err := getEnvironmentVariableValue(ctx, &env, mappingFunc, pod, container, rm, recorder)
+		if err != nil {
+			return err
+		}
+		if val != nil {
+			res[env.Name] = *val
+		}
+	}
+
+	// Append service env vars.
+	for k, v := range svcEnv {
+		if _, present := res[k]; !present {
+			res[k] = v
+		}
+	}
+
+	return nil
+}
+
+func getEnvironmentVariableValue(ctx context.Context, env *corev1.EnvVar, mappingFunc func(string) string, pod *corev1.Pod, container *corev1.Container, rm *manager.ResourceManager, recorder record.EventRecorder) (*string, error) {
 	switch {
 	// Handle values that have been directly provided.
 	case env.Value != "":
 		// Expand variable references
-			res[env.Name] = expansion.Expand(env.Value, mappingFunc)
+		return pointer.StringPtr(expansion.Expand(env.Value, mappingFunc)), nil
-			continue loop
 	// Handle population from a configmap key.
 	case env.ValueFrom != nil && env.ValueFrom.ConfigMapKeyRef != nil:
 		// The environment variable must be set from a configmap.
@@ -342,16 +359,16 @@ loop:
 					recorder.Eventf(pod, corev1.EventTypeWarning, ReasonFailedToReadOptionalConfigMap, "skipping optional envvar %q: failed to read configmap %q", env.Name, vf.Name)
 				}
 				// Continue on to the next reference.
-					continue loop
+				return nil, nil
 			}
 			// At this point we know the key reference is mandatory.
 			// Hence, we should return a meaningful error.
 			if errors.IsNotFound(err) {
 				recorder.Eventf(pod, corev1.EventTypeWarning, ReasonMandatoryConfigMapNotFound, "configmap %q not found", vf.Name)
-					return fmt.Errorf("configmap %q not found", vf.Name)
+				return nil, fmt.Errorf("configmap %q not found", vf.Name)
 			}
 			recorder.Eventf(pod, corev1.EventTypeWarning, ReasonFailedToReadMandatoryConfigMap, "failed to read configmap %q", vf.Name)
-				return fmt.Errorf("failed to read configmap %q: %v", vf.Name, err)
+			return nil, fmt.Errorf("failed to read configmap %q: %v", vf.Name, err)
 		}
 		// At this point we have successfully fetched the target configmap.
 		// We must now try to grab the requested key.
@@ -365,16 +382,15 @@ loop:
 			if optional {
 				// Continue on to the next reference.
 				recorder.Eventf(pod, corev1.EventTypeWarning, ReasonOptionalConfigMapKeyNotFound, "skipping optional envvar %q: key %q does not exist in configmap %q", env.Name, vf.Key, vf.Name)
-					continue loop
+				return nil, nil
 			}
 			// At this point we know the key reference is mandatory.
 			// Hence, we should fail.
 			recorder.Eventf(pod, corev1.EventTypeWarning, ReasonMandatoryConfigMapKeyNotFound, "key %q does not exist in configmap %q", vf.Key, vf.Name)
-				return fmt.Errorf("configmap %q doesn't contain the %q key required by pod %s", vf.Name, vf.Key, pod.Name)
+			return nil, fmt.Errorf("configmap %q doesn't contain the %q key required by pod %s", vf.Name, vf.Key, pod.Name)
 		}
 		// Populate the environment variable and continue on to the next reference.
-			res[env.Name] = keyValue
+		return pointer.StringPtr(keyValue), nil
-			continue loop
 	// Handle population from a secret key.
 	case env.ValueFrom != nil && env.ValueFrom.SecretKeyRef != nil:
 		vf := env.ValueFrom.SecretKeyRef
@@ -394,16 +410,16 @@ loop:
 					recorder.Eventf(pod, corev1.EventTypeWarning, ReasonFailedToReadOptionalSecret, "skipping optional envvar %q: failed to read secret %q", env.Name, vf.Name)
 				}
 				// Continue on to the next reference.
-					continue loop
+				return nil, nil
 			}
 			// At this point we know the key reference is mandatory.
 			// Hence, we should return a meaningful error.
 			if errors.IsNotFound(err) {
 				recorder.Eventf(pod, corev1.EventTypeWarning, ReasonMandatorySecretNotFound, "secret %q not found", vf.Name)
-					return fmt.Errorf("secret %q not found", vf.Name)
+				return nil, fmt.Errorf("secret %q not found", vf.Name)
 			}
 			recorder.Eventf(pod, corev1.EventTypeWarning, ReasonFailedToReadMandatorySecret, "failed to read secret %q", vf.Name)
-				return fmt.Errorf("failed to read secret %q: %v", vf.Name, err)
+			return nil, fmt.Errorf("failed to read secret %q: %v", vf.Name, err)
 		}
 		// At this point we have successfully fetched the target secret.
 		// We must now try to grab the requested key.
@@ -417,16 +433,15 @@ loop:
 			if optional {
 				// Continue on to the next reference.
 				recorder.Eventf(pod, corev1.EventTypeWarning, ReasonOptionalSecretKeyNotFound, "skipping optional envvar %q: key %q does not exist in secret %q", env.Name, vf.Key, vf.Name)
-					continue loop
+				return nil, nil
 			}
 			// At this point we know the key reference is mandatory.
 			// Hence, we should fail.
 			recorder.Eventf(pod, corev1.EventTypeWarning, ReasonMandatorySecretKeyNotFound, "key %q does not exist in secret %q", vf.Key, vf.Name)
-				return fmt.Errorf("secret %q doesn't contain the %q key required by pod %s", vf.Name, vf.Key, pod.Name)
+			return nil, fmt.Errorf("secret %q doesn't contain the %q key required by pod %s", vf.Name, vf.Key, pod.Name)
 		}
 		// Populate the environment variable and continue on to the next reference.
-			res[env.Name] = string(keyValue)
+		return pointer.StringPtr(string(keyValue)), nil
-			continue loop
 	// Handle population from a field (downward API).
 	case env.ValueFrom != nil && env.ValueFrom.FieldRef != nil:
 		// https://github.com/virtual-kubelet/virtual-kubelet/issues/123
@@ -434,27 +449,19 @@ loop:
 
 		runtimeVal, err := podFieldSelectorRuntimeValue(vf, pod)
 		if err != nil {
-				return err
+			return nil, err
 		}
 
-			res[env.Name] = runtimeVal
+		return pointer.StringPtr(runtimeVal), nil
-
-			continue loop
 	// Handle population from a resource request/limit.
 	case env.ValueFrom != nil && env.ValueFrom.ResourceFieldRef != nil:
 		// TODO Implement populating resource requests.
-			continue loop
+		return nil, nil
+	default:
+		// TODO: Should we throw an error here?
+		log.G(ctx).WithField("env", env).Error("Unhandled environment variable, do not know how to populate")
+		return nil, nil
 	}
-	}
-
-	// Append service env vars.
-	for k, v := range svcEnv {
-		if _, present := res[k]; !present {
-			res[k] = v
-		}
-	}
-
-	return nil
 }
 
 // podFieldSelectorRuntimeValue returns the runtime value of the given