feature(leader_election): flag to disable leader election feature on controller (#11064)

charts/ingress-nginx/README.md

@@ -293,6 +293,7 @@ As of version `1.26.0` of this chart, by simply not providing any clusterIP valu
 | controller.containerSecurityContext | object | `{}` | Security context for controller containers |
 | controller.customTemplate.configMapKey | string | `""` |  |
 | controller.customTemplate.configMapName | string | `""` |  |
+| controller.disableLeaderElection | bool | `false` | This configuration disable Nginx Controller Leader Election |
 | controller.dnsConfig | object | `{}` | Optionally customize the pod dnsConfig. |
 | controller.dnsPolicy | string | `"ClusterFirst"` | Optionally change this to ClusterFirstWithHostNet in case you have 'hostNetwork: true'. By default, while using host network, name resolution uses the host's DNS. If you wish nginx-controller to keep resolving names inside the k8s network, use ClusterFirstWithHostNet. |
 | controller.electionID | string | `""` | Election ID to use for status update, by default it uses the controller name combined with a suffix of 'leader' |

charts/ingress-nginx/templates/_params.tpl

@@ -60,6 +60,9 @@
 {{- if .Values.controller.enableTopologyAwareRouting }}
 - --enable-topology-aware-routing=true
 {{- end }}
+{{- if .Values.controller.disableLeaderElection }}
+- --disable-leader-election=true
+{{- end }}
 {{- range $key, $value := .Values.controller.extraArgs }}
 {{- /* Accept keys without values or with false as value */}}
 {{- if eq ($value | quote | len) 2 }}

charts/ingress-nginx/values.yaml

@@ -83,6 +83,8 @@ controller:
   # -- This configuration enables Topology Aware Routing feature, used together with service annotation service.kubernetes.io/topology-mode="auto"
   # Defaults to false
   enableTopologyAwareRouting: false
+  # -- This configuration disable Nginx Controller Leader Election
+  disableLeaderElection: false
   # -- This configuration defines if Ingress Controller should allow users to set
   # their own *-snippet annotations, otherwise this is forbidden / dropped
   # when users add those annotations.

docs/user-guide/cli-arguments.md

@@ -25,6 +25,7 @@ They are set in the container spec of the `ingress-nginx-controller` Deployment
 | `--enable-metrics`                 | Enables the collection of NGINX metrics. (default true) |
 | `--enable-ssl-chain-completion`    | Autocomplete SSL certificate chains with missing intermediate CA certificates. Certificates uploaded to Kubernetes must have the "Authority Information Access" X.509 v3 extension for this to succeed. (default false)|
 | `--enable-ssl-passthrough`         | Enable SSL Passthrough. (default false) |
+| `--disable-leader-election`        | Disable Leader Election on Nginx Controller. (default false) |
 | `--enable-topology-aware-routing`  | Enable topology aware routing feature, needs service object annotation service.kubernetes.io/topology-mode sets to auto. (default false) |
 | `--exclude-socket-metrics`         | Set of socket request metrics to exclude which won't be exported nor being calculated. The possible socket request metrics to exclude are documented in the monitoring guide e.g. 'nginx_ingress_controller_request_duration_seconds,nginx_ingress_controller_response_size'|
 | `--health-check-path`              | URL path of the health check endpoint. Configured inside the NGINX status server. All requests received on the port defined by the healthz-port parameter are forwarded internally to this path. (default "/healthz") |

internal/ingress/controller/controller.go

@@ -100,6 +100,8 @@ type Configuration struct {
 
 	EnableSSLPassthrough bool
 
+	DisableLeaderElection bool
+
 	EnableProfiling bool
 
 	EnableMetrics        bool

internal/ingress/controller/nginx.go

@@ -271,8 +271,9 @@ func (n *NGINXController) Start() {
 	// TODO: For now, as the the IngressClass logics has changed, is up to the
 	// cluster admin to create different Leader Election IDs.
 	// Should revisit this in a future
-	electionID := n.cfg.ElectionID
 
+	if !n.cfg.DisableLeaderElection {
+		electionID := n.cfg.ElectionID
 		setupLeaderElection(&leaderElectionConfig{
 			Client:     n.cfg.Client,
 			ElectionID: electionID,
@@ -291,6 +292,7 @@ func (n *NGINXController) Start() {
 				n.metricCollector.OnStoppedLeading(electionID)
 			},
 		})
+	}
 
 	cmd := n.command.ExecCommand()
 

pkg/flags/flags.go

@@ -146,6 +146,9 @@ Requires the update-status parameter.`)
 		enableSSLPassthrough = flags.Bool("enable-ssl-passthrough", false,
 			`Enable SSL Passthrough.`)
 
+		disableLeaderElection = flags.Bool("disable-leader-election", false,
+			`Disable Leader Election on NGINX Controller.`)
+
 		disableServiceExternalName = flags.Bool("disable-svc-external-name", false,
 			`Disable support for Services of type ExternalName.`)
 
@@ -333,6 +336,7 @@ https://blog.maxmind.com/2019/12/18/significant-changes-to-accessing-and-using-g
 		MonitorMaxBatchSize:         *monitorMaxBatchSize,
 		DisableServiceExternalName:  *disableServiceExternalName,
 		EnableSSLPassthrough:        *enableSSLPassthrough,
+		DisableLeaderElection:       *disableLeaderElection,
 		ResyncPeriod:                *resyncPeriod,
 		DefaultService:              *defaultSvc,
 		Namespace:                   *watchNamespace,

pkg/flags/flags_test.go

@@ -109,3 +109,37 @@ func TestMaxmindRetryDownload(t *testing.T) {
 		t.Fatalf("Expected an error parsing flags but none returned")
 	}
 }
+
+func TestDisableLeaderElectionFlag(t *testing.T) {
+	ResetForTesting(func() { t.Fatal("Parsing failed") })
+
+	oldArgs := os.Args
+	defer func() { os.Args = oldArgs }()
+	os.Args = []string{"cmd", "--disable-leader-election", "--http-port", "80", "--https-port", "443"}
+
+	_, conf, err := ParseFlags()
+	if err != nil {
+		t.Fatalf("Unexpected error parsing default flags: %v", err)
+	}
+
+	if !conf.DisableLeaderElection {
+		t.Fatalf("Expected --disable-leader-election and conf.DisableLeaderElection as true, but found: %v", conf.DisableLeaderElection)
+	}
+}
+
+func TestIfLeaderElectionDisabledFlagIsFalse(t *testing.T) {
+	ResetForTesting(func() { t.Fatal("Parsing failed") })
+
+	oldArgs := os.Args
+	defer func() { os.Args = oldArgs }()
+	os.Args = []string{"cmd", "--http-port", "80", "--https-port", "443"}
+
+	_, conf, err := ParseFlags()
+	if err != nil {
+		t.Fatalf("Unexpected error parsing default flags: %v", err)
+	}
+
+	if conf.DisableLeaderElection {
+		t.Fatalf("Expected --disable-leader-election and conf.DisableLeaderElection as false, but found: %v", conf.DisableLeaderElection)
+	}
+}

test/e2e-image/namespace-overlays/disableleaderelection/values.yaml

@@ -0,0 +1,34 @@
+# TODO: remove the need to use fullnameOverride
+fullnameOverride: nginx-ingress
+controller:
+  image:
+    repository: ingress-controller/controller
+    chroot: true
+    tag: 1.0.0-dev
+    digest:
+    digestChroot:
+  scope:
+    # Necessary to allow the ingress controller to get the topology information from the nodes
+    enabled: false
+  config:
+    worker-processes: "1"
+  readinessProbe:
+    initialDelaySeconds: 3
+    periodSeconds: 1
+  livenessProbe:
+    initialDelaySeconds: 3
+    periodSeconds: 1
+  service:
+    type: NodePort
+  extraArgs:
+    # e2e tests do not require information about ingress status
+    update-status: "false"
+  terminationGracePeriodSeconds: 1
+  admissionWebhooks:
+    enabled: false
+
+  disableLeaderElection: true
+
+rbac:
+  create: true
+  scope: false

test/e2e/disableleaderelection/disable_leader.go

@@ -0,0 +1,93 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package disableleaderelection
+
+import (
+	"net/http"
+	"strings"
+
+	"github.com/onsi/ginkgo/v2"
+
+	"k8s.io/ingress-nginx/test/e2e/framework"
+)
+
+var _ = framework.IngressNginxDescribe("[Disable Leader] Routing works when leader election was disabled", func() {
+	f := framework.NewDefaultFramework("disableleaderelection")
+
+	ginkgo.BeforeEach(func() {
+		f.NewEchoDeployment()
+	})
+
+	ginkgo.It("should create multiple ingress routings rules when leader election has disabled", func() {
+		host1 := "leader.election.disabled.com"
+		host2 := "leader.election.disabled2.com"
+
+		ing1 := framework.NewSingleIngress(host1, "/foo", host1, f.Namespace, framework.EchoService, 80, nil)
+		f.EnsureIngress(ing1)
+
+		ing2 := framework.NewSingleIngress(host2, "/ping", host2, f.Namespace, framework.EchoService, 80, nil)
+		f.EnsureIngress(ing2)
+
+		f.WaitForNginxServer(host1,
+			func(server string) bool {
+				return strings.Contains(server, host1) &&
+					strings.Contains(server, "location /foo")
+			})
+
+		f.WaitForNginxServer(host2,
+			func(server string) bool {
+				return strings.Contains(server, host2) &&
+					strings.Contains(server, "location /ping")
+			})
+
+		f.HTTPTestClient().
+			GET("/foo").
+			WithHeader("Host", host1).
+			Expect().
+			Status(http.StatusOK)
+
+		f.HTTPTestClient().
+			GET("/bar").
+			WithHeader("Host", host1).
+			Expect().
+			Status(http.StatusNotFound)
+
+		f.HTTPTestClient().
+			GET("/foo").
+			WithHeader("Host", host2).
+			Expect().
+			Status(http.StatusNotFound)
+
+		f.HTTPTestClient().
+			GET("/ping").
+			WithHeader("Host", host2).
+			Expect().
+			Status(http.StatusOK)
+
+		f.HTTPTestClient().
+			GET("/pong").
+			WithHeader("Host", host2).
+			Expect().
+			Status(http.StatusNotFound)
+
+		f.HTTPTestClient().
+			GET("/ping").
+			WithHeader("Host", host1).
+			Expect().
+			Status(http.StatusNotFound)
+	})
+})

test/e2e/e2e.go

@@ -34,6 +34,7 @@ import (
 	_ "k8s.io/ingress-nginx/test/e2e/annotations/modsecurity"
 	_ "k8s.io/ingress-nginx/test/e2e/dbg"
 	_ "k8s.io/ingress-nginx/test/e2e/defaultbackend"
+	_ "k8s.io/ingress-nginx/test/e2e/disableleaderelection"
 	_ "k8s.io/ingress-nginx/test/e2e/endpointslices"
 	_ "k8s.io/ingress-nginx/test/e2e/gracefulshutdown"
 	_ "k8s.io/ingress-nginx/test/e2e/ingress"