feat(mgr) deprecate --leader-elect flag

Deprecate the --leader-elect flag. It is no longer used. Leader election
is enabled or disabled based on whether the instance is running in
DB-less mode or not.

CHANGELOG.md

@@ -51,8 +51,9 @@ the `configuration.konghq.com` API group.
 
 #### Breaking changes
 
-- The `--leader-elect` flag has been removed. Leader election is now enabled or
-  disabled automatically based on the database mode.
+- The `--leader-elect` flag has been deprectated and will be removed in a
+  future release. Leader election is now enabled or disabled automatically
+  based on the database mode. The flag is no longer honored.
   [#2053](https://github.com/Kong/kubernetes-ingress-controller/issues/2053)
 - You must upgrade to 2.0.x before upgrading to 2.1.x to properly handle the
   transition from apiextensions.k8s.io/v1beta1 CRDs to apiextensions.k8s.io/v1

internal/manager/config.go

@@ -131,7 +131,7 @@ func (c *Config) FlagSet() *pflag.FlagSet {
 	// Kubernetes configurations
 	flagSet.StringVar(&c.KubeconfigPath, "kubeconfig", "", "Path to the kubeconfig file.")
 	flagSet.StringVar(&c.IngressClassName, "ingress-class", annotations.DefaultIngressClass, `Name of the ingress class to route through this controller.`)
-	flagSet.BoolVar(&c.EnableLeaderElection, "leader-elect", false, "Enable leader election for controller manager. Enabling this will ensure there is only one active controller manager.")
+	flagSet.BoolVar(&c.EnableLeaderElection, "leader-elect", false, "DEPRECATED as of 2.1.0 leader election behavior is determined automatically and this flag has no effect")
 	flagSet.StringVar(&c.LeaderElectionID, "election-id", "5b374a9e.konghq.com", `Election id to use for status update.`)
 	flagSet.StringVar(&c.LeaderElectionNamespace, "election-namespace", "", `Leader election namespace to use when running outside a cluster`)
 	flagSet.StringSliceVar(&c.FilterTags, "kong-admin-filter-tag", []string{"managed-by-ingress-controller"}, "The tag used to manage and filter entities in Kong. This flag can be specified multiple times to specify multiple tags. This setting will be silently ignored if the Kong instance has no tags support.")

internal/manager/run.go

@@ -43,6 +43,10 @@ func Run(ctx context.Context, c *Config, diagnostic util.ConfigDumpDiagnostic) e
 	utilruntime.Must(knativev1alpha1.AddToScheme(scheme))
 	utilruntime.Must(gatewayv1alpha2.AddToScheme(scheme))
 
+	if c.EnableLeaderElection {
+		setupLog.V(0).Info("the --leader-elect flag is deprecated and no longer has any effect: leader election is set based on the Kong database setting")
+	}
+
 	setupLog.Info("getting enabled options and features")
 	featureGates, err := setupFeatureGates(setupLog, c)
 	if err != nil {