Initial implementation of managed labels

See #47. This is the initial implementation of managed labels and
annotations - that is, the ability to set a label (or annotation) in a
HierarchyConfiguration object, and have that label (...) propagated to
all descendants, similar to the way objects are propagated. As with
objects, only allowlisted labels are propagated, as defined by the
command line option '--managed-namespace-[label|annotation]'.

Still to come: validator support, better conditions for conflicts,
better testing for external namespaces, better testing for more regexes,
documentation, end-to-end tests.

Tested: see new integ tests.

api/v1alpha2/hierarchy_types.go

@@ -55,12 +55,14 @@ const (
 	ConditionBadConfiguration string = "BadConfiguration"
 
 	// Condition reasons.
-	ReasonAncestor      string = "AncestorHaltActivities"
-	ReasonDeletingCRD   string = "DeletingCRD"
-	ReasonInCycle       string = "InCycle"
-	ReasonParentMissing string = "ParentMissing"
-	ReasonIllegalParent string = "IllegalParent"
-	ReasonAnchorMissing string = "SubnamespaceAnchorMissing"
+	ReasonAncestor                 string = "AncestorHaltActivities"
+	ReasonDeletingCRD              string = "DeletingCRD"
+	ReasonInCycle                  string = "InCycle"
+	ReasonParentMissing            string = "ParentMissing"
+	ReasonIllegalParent            string = "IllegalParent"
+	ReasonAnchorMissing            string = "SubnamespaceAnchorMissing"
+	ReasonIllegalManagedLabel      string = "IllegalManagedLabel"
+	ReasonIllegalManagedAnnotation string = "IllegalManagedAnnotation"
 )
 
 // AllConditions have all the conditions by type and reason. Please keep this
@@ -124,6 +126,18 @@ type HierarchyConfigurationSpec struct {
 	// AllowCascadingDeletion indicates if the subnamespaces of this namespace are
 	// allowed to cascading delete.
 	AllowCascadingDeletion bool `json:"allowCascadingDeletion,omitempty"`
+
+	// Lables is a list of labels and values to apply to the current namespace and all of its
+	// descendants. All label keys must match a regex specified on the command line by
+	// --managed-namespace-label. A namespace cannot have a KVP that conflicts with one of its
+	// ancestors.
+	Labels []MetaKVP `json:"labels,omitempty"`
+
+	// Annotations is a list of annotations and values to apply to the current namespace and all of
+	// its descendants. All annotation keys must match a regex specified on the command line by
+	// --managed-namespace-annotation. A namespace cannot have a KVP that conflicts with one of its
+	// ancestors.
+	Annotations []MetaKVP `json:"annotations,omitempty"`
 }
 
 // HierarchyStatus defines the observed state of Hierarchy
@@ -147,6 +161,18 @@ type HierarchyConfigurationList struct {
 	Items           []HierarchyConfiguration `json:"items"`
 }
 
+// MetaKVP represents a label or annotation
+type MetaKVP struct {
+	// Key is the name of the label or annotation. It must conform to the normal rules for Kubernetes
+	// label/annotation keys.
+	Key string `json:"key"`
+
+	// Value is the value of the label or annotation. It must confirm to the normal rules for
+	// Kubernetes label or annoation values, which are far more restrictive for labels than for
+	// anntations.
+	Value string `json:"value"`
+}
+
 // metav1.Condition is introduced in k8s.io/apimachinery v0.20.0-alpha.1 and we
 // don't want to take a dependency on it yet, thus we copied the below struct from
 // https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/types.go:

cmd/manager/main.go

@@ -65,6 +65,8 @@ var (
 	restartOnSecretRefresh  bool
 	unpropagatedAnnotations arrayArg
 	excludedNamespaces      arrayArg
+	managedNamespaceLabels  arrayArg
+	managedNamespaceAnnots  arrayArg
 	includedNamespacesRegex string
 )
 
@@ -97,13 +99,19 @@ func main() {
 	flag.IntVar(&webhookServerPort, "webhook-server-port", 443, "The port that the webhook server serves at.")
 	flag.Var(&unpropagatedAnnotations, "unpropagated-annotation", "An annotation that, if present, will be stripped out of any propagated copies of an object. May be specified multiple times, with each instance specifying one annotation. See the user guide for more information.")
 	flag.Var(&excludedNamespaces, "excluded-namespace", "A namespace that, if present, will be excluded from HNC management. May be specified multiple times, with each instance specifying one namespace. See the user guide for more information.")
-	flag.StringVar(&includedNamespacesRegex, "included-namespace-regex", ".*", "Namespace regular expression. Namespaces that match this regexp will be included and handle by HNC. As it is a regex, this parameter cannot be specified multiple times. Implicit wrapping of the expression \"^...$\" is done here")
+	flag.StringVar(&includedNamespacesRegex, "included-namespace-regex", ".*", "Namespace regular expression. Namespaces that match this regexp will be included and handle by HNC. The regex is implicitly wrapped by \"^...$\" and may only be specified once.")
 	flag.BoolVar(&restartOnSecretRefresh, "cert-restart-on-secret-refresh", false, "Kills the process when secrets are refreshed so that the pod can be restarted (secrets take up to 60s to be updated by running pods)")
+	flag.Var(&managedNamespaceLabels, "managed-namespace-label", "A regex indicating the labels on namespaces that are managed by HNC. These labels may only be set via the HierarchyConfiguration object. All regexes are implictly wrapped by \"^...$\". This argument can be specified multiple times. See the user guide for more information.")
+	flag.Var(&managedNamespaceAnnots, "managed-namespace-annotation", "A regex indicating the annotations on namespaces that are managed by HNC. These annotations may only be set via the HierarchyConfiguration object. All regexes are implictly wrapped by \"^...$\". This argument can be specified multiple times. See the user guide for more information.")
 	flag.Parse()
+
 	// Assign the array args to the configuration variables after the args are parsed.
 	config.UnpropagatedAnnotations = unpropagatedAnnotations
-
 	config.SetNamespaces(includedNamespacesRegex, excludedNamespaces...)
+	if err := config.SetManagedMeta(managedNamespaceLabels, managedNamespaceAnnots); err != nil {
+		setupLog.Error(err, "Illegal flag values")
+		os.Exit(1)
+	}
 
 	// Enable OpenCensus exporters to export metrics
 	// to Stackdriver Monitoring.

config/crd/bases/hnc.x-k8s.io_hierarchyconfigurations.yaml

@@ -46,6 +46,54 @@ spec:
                 description: AllowCascadingDeletion indicates if the subnamespaces
                   of this namespace are allowed to cascading delete.
                 type: boolean
+              annotations:
+                description: Annotations is a list of annotations and values to apply
+                  to the current namespace and all of its descendants. All annotation
+                  keys must match a regex specified on the command line by --managed-namespace-annotation.
+                  A namespace cannot have a KVP that conflicts with one of its ancestors.
+                items:
+                  description: MetaKVP represents a label or annotation
+                  properties:
+                    key:
+                      description: Key is the name of the label or annotation. It
+                        must conform to the normal rules for Kubernetes label/annotation
+                        keys.
+                      type: string
+                    value:
+                      description: Value is the value of the label or annotation.
+                        It must confirm to the normal rules for Kubernetes label or
+                        annoation values, which are far more restrictive for labels
+                        than for anntations.
+                      type: string
+                  required:
+                  - key
+                  - value
+                  type: object
+                type: array
+              labels:
+                description: Lables is a list of labels and values to apply to the
+                  current namespace and all of its descendants. All label keys must
+                  match a regex specified on the command line by --managed-namespace-label.
+                  A namespace cannot have a KVP that conflicts with one of its ancestors.
+                items:
+                  description: MetaKVP represents a label or annotation
+                  properties:
+                    key:
+                      description: Key is the name of the label or annotation. It
+                        must conform to the normal rules for Kubernetes label/annotation
+                        keys.
+                      type: string
+                    value:
+                      description: Value is the value of the label or annotation.
+                        It must confirm to the normal rules for Kubernetes label or
+                        annoation values, which are far more restrictive for labels
+                        than for anntations.
+                      type: string
+                  required:
+                  - key
+                  - value
+                  type: object
+                type: array
               parent:
                 description: Parent indicates the parent of this namespace, if any.
                 type: string

internal/config/namespace.go

@@ -1,7 +1,10 @@
 package config
 
 import (
+	"fmt"
 	"regexp"
+
+	api "sigs.k8s.io/hierarchical-namespaces/api/v1alpha2"
 )
 
 var (
@@ -18,6 +21,16 @@ var (
 	// includedNamespacesStr is the original pattern of the regex. It must
 	// only be used to generate error messages.
 	includedNamespacesStr string
+
+	// managedLabels is the list of compiled regexes for managed labels. Any label in this list is
+	// removed from all managed namespaces unless specifically specified by the HC of the namespace or
+	// one of its ancestors.
+	managedLabels []*regexp.Regexp
+
+	// managedAnnotations is the list of compiled regexes for managed annotations. Any annotations in
+	// this list is removed from all managed namespaces unless specifically specified by the HC of the
+	// namespace or one of its ancestors.
+	managedAnnotations []*regexp.Regexp
 )
 
 func SetNamespaces(regex string, excluded ...string) {
@@ -63,3 +76,52 @@ func WhyUnmanaged(nm string) string {
 func IsManagedNamespace(nm string) bool {
 	return WhyUnmanaged(nm) == ""
 }
+
+// SetManagedMeta sets the regexes for the managed namespace labels and annotations. The function
+// ensures that all strings are valid regexes, and that they do not attempt to select for HNC
+// metadata.
+func SetManagedMeta(labels, annots []string) error {
+	if err := setManagedMeta(labels, "--managed-namespace-label", &managedLabels); err != nil {
+		return err
+	}
+	if err := setManagedMeta(annots, "--managed-namespace-annotation", &managedAnnotations); err != nil {
+		return err
+	}
+	return nil
+}
+
+func setManagedMeta(patterns []string, option string, regexes *[]*regexp.Regexp) error {
+	// Reset (useful for unit tests)
+	*regexes = nil
+
+	// Validate regexes
+	for _, p := range patterns {
+		r, err := regexp.Compile("^" + p + "$")
+		if err != nil {
+			return fmt.Errorf("Illegal value for %s %q: %w", option, p, err)
+		}
+		if r.MatchString(api.MetaGroup) {
+			return fmt.Errorf("Illegal value for %s %q: cannot specify a pattern that matches %q", option, p, api.MetaGroup)
+		}
+		*regexes = append(*regexes, r)
+	}
+	return nil
+}
+
+func IsManagedLabel(k string) bool {
+	for _, regex := range managedLabels {
+		if regex.MatchString(k) {
+			return true
+		}
+	}
+	return false
+}
+
+func IsManagedAnnotation(k string) bool {
+	for _, regex := range managedAnnotations {
+		if regex.MatchString(k) {
+			return true
+		}
+	}
+	return false
+}

internal/forest/namespace.go

@@ -32,6 +32,14 @@ type Namespace struct {
 	// and to store the tree labels of external namespaces.
 	labels map[string]string
 
+	// ManagedLabels are all managed labels explicitly set on this namespace (i.e., excluding anything
+	// set by ancestors).
+	ManagedLabels map[string]string
+
+	// ManagedAnnotations are all managed annotations explicitly set on this namespace (i.e.,
+	// excluding anything set by ancestors).
+	ManagedAnnotations map[string]string
+
 	// sourceObjects store the objects created by users, identified by GVK and name.
 	// It serves as the source of truth for object controllers to propagate objects.
 	sourceObjects objects