From b7561613a41a7759668636e9a69fa377d7989f84 Mon Sep 17 00:00:00 2001
From: Jonathan Stacks <jonstacks@users.noreply.github.com>
Date: Thu, 5 Jan 2023 17:37:58 -0600
Subject: [PATCH] :sparkles: Add controller option for setting leader election
 (#2117)

* Add controller option for overrding the need for leader election

* Update Options to be clearer

Addresses PR review comment
---
 pkg/controller/controller.go          |  5 +++
 pkg/controller/controller_test.go     | 44 +++++++++++++++++++++++++++
 pkg/internal/controller/controller.go | 11 +++++++
 3 files changed, 60 insertions(+)

diff --git a/pkg/controller/controller.go b/pkg/controller/controller.go
index fe7f94fdc1..8e0a9a91de 100644
--- a/pkg/controller/controller.go
+++ b/pkg/controller/controller.go
@@ -58,6 +58,10 @@ type Options struct {
 	// RecoverPanic indicates whether the panic caused by reconcile should be recovered.
 	// Defaults to the Controller.RecoverPanic setting from the Manager if unset.
 	RecoverPanic *bool
+
+	// NeedLeaderElection indicates whether the controller needs to use leader election.
+	// Defaults to true, which means the controller will use leader election.
+	NeedLeaderElection *bool
 }
 
 // Controller implements a Kubernetes API.  A Controller manages a work queue fed reconcile.Requests
@@ -156,6 +160,7 @@ func NewUnmanaged(name string, mgr manager.Manager, options Options) (Controller
 		Name:                    name,
 		LogConstructor:          options.LogConstructor,
 		RecoverPanic:            options.RecoverPanic,
+		LeaderElected:           options.NeedLeaderElection,
 	}, nil
 }
 
diff --git a/pkg/controller/controller_test.go b/pkg/controller/controller_test.go
index b5d816bc28..66e11b7d50 100644
--- a/pkg/controller/controller_test.go
+++ b/pkg/controller/controller_test.go
@@ -178,6 +178,50 @@ var _ = Describe("controller.Controller", func() {
 			Expect(ctrl.RecoverPanic).NotTo(BeNil())
 			Expect(*ctrl.RecoverPanic).To(BeFalse())
 		})
+
+		It("should default NeedLeaderElection on the controller to true", func() {
+			m, err := manager.New(cfg, manager.Options{})
+			Expect(err).NotTo(HaveOccurred())
+
+			c, err := controller.New("new-controller", m, controller.Options{
+				Reconciler: rec,
+			})
+			Expect(err).NotTo(HaveOccurred())
+
+			ctrl, ok := c.(*internalcontroller.Controller)
+			Expect(ok).To(BeTrue())
+
+			Expect(ctrl.NeedLeaderElection()).To(BeTrue())
+		})
+
+		It("should allow for setting leaderElected to false", func() {
+			m, err := manager.New(cfg, manager.Options{})
+			Expect(err).NotTo(HaveOccurred())
+
+			c, err := controller.New("new-controller", m, controller.Options{
+				Reconciler:         rec,
+				NeedLeaderElection: pointer.Bool(false),
+			})
+			Expect(err).NotTo(HaveOccurred())
+
+			ctrl, ok := c.(*internalcontroller.Controller)
+			Expect(ok).To(BeTrue())
+
+			Expect(ctrl.NeedLeaderElection()).To(BeFalse())
+		})
+
+		It("should implement manager.LeaderElectionRunnable", func() {
+			m, err := manager.New(cfg, manager.Options{})
+			Expect(err).NotTo(HaveOccurred())
+
+			c, err := controller.New("new-controller", m, controller.Options{
+				Reconciler: rec,
+			})
+			Expect(err).NotTo(HaveOccurred())
+
+			_, ok := c.(manager.LeaderElectionRunnable)
+			Expect(ok).To(BeTrue())
+		})
 	})
 })
 
diff --git a/pkg/internal/controller/controller.go b/pkg/internal/controller/controller.go
index f7734695ce..1f8f8b7398 100644
--- a/pkg/internal/controller/controller.go
+++ b/pkg/internal/controller/controller.go
@@ -93,6 +93,9 @@ type Controller struct {
 
 	// RecoverPanic indicates whether the panic caused by reconcile should be recovered.
 	RecoverPanic *bool
+
+	// LeaderElected indicates whether the controller is leader elected or always running.
+	LeaderElected *bool
 }
 
 // watchDescription contains all the information necessary to start a watch.
@@ -152,6 +155,14 @@ func (c *Controller) Watch(src source.Source, evthdler handler.EventHandler, prc
 	return src.Start(c.ctx, evthdler, c.Queue, prct...)
 }
 
+// NeedLeaderElection implements the manager.LeaderElectionRunnable interface.
+func (c *Controller) NeedLeaderElection() bool {
+	if c.LeaderElected == nil {
+		return true
+	}
+	return *c.LeaderElected
+}
+
 // Start implements controller.Controller.
 func (c *Controller) Start(ctx context.Context) error {
 	// use an IIFE to get proper lock handling