From a850279cbbf903c15c5c29ed307b5e21fc9609b9 Mon Sep 17 00:00:00 2001
From: Amine <hilalyamine@gmail.com>
Date: Mon, 19 Jan 2026 21:49:00 -0800
Subject: [PATCH] feat: add enable-controller-warmup flag

Wire EnableWarmup controller-runtime config to CLI flag and helm values.
---
 templates/cmd/controller/main.go.tpl         | 6 ++++++
 templates/helm/templates/deployment.yaml.tpl | 3 +++
 templates/helm/values.yaml.tpl               | 4 ++++
 3 files changed, 13 insertions(+)

diff --git a/templates/cmd/controller/main.go.tpl b/templates/cmd/controller/main.go.tpl
index 74f65b15..3a1f820a 100644
--- a/templates/cmd/controller/main.go.tpl
+++ b/templates/cmd/controller/main.go.tpl
@@ -18,6 +18,7 @@ import (
 	clientgoscheme "k8s.io/client-go/kubernetes/scheme"
 	ctrlrt "sigs.k8s.io/controller-runtime"
 	ctrlrtcache "sigs.k8s.io/controller-runtime/pkg/cache"
+	ctrlrtconfig "sigs.k8s.io/controller-runtime/pkg/config"
 	ctrlrthealthz "sigs.k8s.io/controller-runtime/pkg/healthz"
 	ctrlrtmetrics "sigs.k8s.io/controller-runtime/pkg/metrics"
 	metricsserver "sigs.k8s.io/controller-runtime/pkg/metrics/server"
@@ -128,6 +129,11 @@ func main() {
 				Host: host,
 			},
 		},
+		Controller: ctrlrtconfig.Controller{
+			// EnableWarmup allows controllers to start their sources (watches/informers) before
+			// leader election is won. This pre-populates caches and improves leader failover time.
+			EnableWarmup: &ackCfg.EnableControllerWarmup,
+		},
 		Metrics:                 metricsserver.Options{BindAddress: ackCfg.MetricsAddr},
 		LeaderElection:          ackCfg.EnableLeaderElection,
 		LeaderElectionID:        "ack-" + awsServiceAPIGroup,
diff --git a/templates/helm/templates/deployment.yaml.tpl b/templates/helm/templates/deployment.yaml.tpl
index 3c039908..0309eff0 100644
--- a/templates/helm/templates/deployment.yaml.tpl
+++ b/templates/helm/templates/deployment.yaml.tpl
@@ -77,6 +77,9 @@ spec:
         - --enable-leader-election
         - --leader-election-namespace
         - "$(LEADER_ELECTION_NAMESPACE)"
+{{ "{{- if .Values.leaderElection.enableControllerWarmup }}" }}
+        - --enable-controller-warmup
+{{ "{{- end }}" }}
 {{ "{{- end }}" }}
 {{ "{{- if gt (int .Values.reconcile.defaultResyncPeriod) 0 }}" }}
         - --reconcile-default-resync-seconds
diff --git a/templates/helm/values.yaml.tpl b/templates/helm/values.yaml.tpl
index d337ce6a..15617b62 100644
--- a/templates/helm/values.yaml.tpl
+++ b/templates/helm/values.yaml.tpl
@@ -173,6 +173,10 @@ leaderElection:
   # will attempt to use the namespace of the service account mounted to the Controller
   # pod.
   namespace: ""
+  # Enable controller warmup to start controller sources (watches/informers) before
+  # leader election is won. This pre-populates caches and improves leader failover time.
+  # Requires leader election to be enabled.
+  enableControllerWarmup: false
 
 # Enable Cross Account Resource Management (default = true). Set this to false to disable cross account resource management.
 enableCARM: true