feat: add pod anti-affinity for multi-replica cloudflared connector

pkg/controller/controlled-cloudflared-connector.go

@@ -3,6 +3,7 @@ package controller
 import (
 	"context"
 	"os"
+	"reflect"
 	"slices"
 	"strconv"
 
@@ -71,6 +72,12 @@ func CreateOrUpdateControlledCloudflared(
 			}
 		}
 
+		// Check if anti-affinity needs to be added or removed
+		desiredAffinity := buildPodAntiAffinity("controlled-cloudflared-connector", desiredReplicas)
+		if !affinityEqual(existingDeployment.Spec.Template.Spec.Affinity, desiredAffinity) {
+			needsUpdate = true
+		}
+
 		if needsUpdate {
 
 			updatedDeployment := cloudflaredConnectDeploymentTemplating(protocol, token, namespace, desiredReplicas, extraArgs)
@@ -144,6 +151,7 @@ func cloudflaredConnectDeploymentTemplating(protocol string, token string, names
 					},
 				},
 				Spec: v1.PodSpec{
+					Affinity:  buildPodAntiAffinity(appName, replicas),
 					Containers: []v1.Container{
 						{
 							Name:            appName,
@@ -159,6 +167,39 @@ func cloudflaredConnectDeploymentTemplating(protocol string, token string, names
 	}
 }
 
+// buildPodAntiAffinity returns a pod anti-affinity that spreads pods across nodes.
+// Returns nil when replicas <= 1 (no point scheduling constraints for a single pod).
+func buildPodAntiAffinity(appName string, replicas int32) *v1.Affinity {
+	if replicas <= 1 {
+		return nil
+	}
+	return &v1.Affinity{
+		PodAntiAffinity: &v1.PodAntiAffinity{
+			RequiredDuringSchedulingIgnoredDuringExecution: []v1.PodAffinityTerm{
+				{
+					LabelSelector: &metav1.LabelSelector{
+						MatchLabels: map[string]string{
+							"app": appName,
+						},
+					},
+					TopologyKey: "kubernetes.io/hostname",
+				},
+			},
+		},
+	}
+}
+
+// affinityEqual compares two Affinity pointers for equality.
+func affinityEqual(a, b *v1.Affinity) bool {
+	if a == nil && b == nil {
+		return true
+	}
+	if a == nil || b == nil {
+		return false
+	}
+	return reflect.DeepEqual(a, b)
+}
+
 func getDesiredReplicas() (int32, error) {
 	replicaCount := os.Getenv("CLOUDFLARED_REPLICA_COUNT")
 	if replicaCount == "" {
@@ -190,4 +231,3 @@ func buildCloudflaredCommand(protocol string, token string, extraArgs []string)
 
 	return command
 }
-

pkg/controller/controlled-cloudflared-connector_test.go

@@ -3,7 +3,11 @@ package controller
 import (
 	"testing"
 
+	v1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestBuildCloudflaredCommand(t *testing.T) {
@@ -100,3 +104,100 @@ func TestBuildCloudflaredCommand(t *testing.T) {
 	}
 }
 
+func TestCloudflaredConnectDeploymentTemplating(t *testing.T) {
+	t.Run("single replica has no anti-affinity", func(t *testing.T) {
+		dep := cloudflaredConnectDeploymentTemplating("quic", "tok", "ns", 1, nil)
+
+		assert.Equal(t, "controlled-cloudflared-connector", dep.Name)
+		assert.Equal(t, "ns", dep.Namespace)
+		assert.Equal(t, int32(1), *dep.Spec.Replicas)
+		assert.Nil(t, dep.Spec.Template.Spec.Affinity, "single replica should have no affinity")
+	})
+
+	t.Run("multiple replicas have anti-affinity", func(t *testing.T) {
+		dep := cloudflaredConnectDeploymentTemplating("quic", "tok", "ns", 3, nil)
+
+		assert.Equal(t, int32(3), *dep.Spec.Replicas)
+		require.NotNil(t, dep.Spec.Template.Spec.Affinity)
+		require.NotNil(t, dep.Spec.Template.Spec.Affinity.PodAntiAffinity)
+
+		terms := dep.Spec.Template.Spec.Affinity.PodAntiAffinity.RequiredDuringSchedulingIgnoredDuringExecution
+		require.Len(t, terms, 1)
+		assert.Equal(t, "kubernetes.io/hostname", terms[0].TopologyKey)
+		assert.Equal(t, map[string]string{"app": "controlled-cloudflared-connector"}, terms[0].LabelSelector.MatchLabels)
+	})
+
+	t.Run("labels are consistent across object meta, selector, and template", func(t *testing.T) {
+		dep := cloudflaredConnectDeploymentTemplating("quic", "tok", "ns", 2, nil)
+
+		expectedLabels := map[string]string{
+			"app": "controlled-cloudflared-connector",
+			"strrl.dev/cloudflare-tunnel-ingress-controller": "controlled-cloudflared-connector",
+		}
+		assert.Equal(t, expectedLabels, dep.Labels)
+		assert.Equal(t, expectedLabels, dep.Spec.Selector.MatchLabels)
+		assert.Equal(t, expectedLabels, dep.Spec.Template.Labels)
+	})
+
+	t.Run("container uses provided protocol and token", func(t *testing.T) {
+		dep := cloudflaredConnectDeploymentTemplating("http2", "my-token", "default", 1, []string{"--post-quantum"})
+
+		require.Len(t, dep.Spec.Template.Spec.Containers, 1)
+		c := dep.Spec.Template.Spec.Containers[0]
+		assert.Equal(t, "controlled-cloudflared-connector", c.Name)
+		assert.Contains(t, c.Command, "http2")
+		assert.Contains(t, c.Command, "my-token")
+		assert.Contains(t, c.Command, "--post-quantum")
+	})
+}
+
+func TestBuildPodAntiAffinity(t *testing.T) {
+	t.Run("nil for single replica", func(t *testing.T) {
+		assert.Nil(t, buildPodAntiAffinity("app", 1))
+	})
+
+	t.Run("nil for zero replicas", func(t *testing.T) {
+		assert.Nil(t, buildPodAntiAffinity("app", 0))
+	})
+
+	t.Run("set for multiple replicas", func(t *testing.T) {
+		aff := buildPodAntiAffinity("my-app", 3)
+		require.NotNil(t, aff)
+		terms := aff.PodAntiAffinity.RequiredDuringSchedulingIgnoredDuringExecution
+		require.Len(t, terms, 1)
+		assert.Equal(t, "kubernetes.io/hostname", terms[0].TopologyKey)
+		assert.Equal(t, map[string]string{"app": "my-app"}, terms[0].LabelSelector.MatchLabels)
+	})
+}
+
+func TestAffinityEqual(t *testing.T) {
+	aff1 := &v1.Affinity{
+		PodAntiAffinity: &v1.PodAntiAffinity{
+			RequiredDuringSchedulingIgnoredDuringExecution: []v1.PodAffinityTerm{
+				{
+					LabelSelector: &metav1.LabelSelector{
+						MatchLabels: map[string]string{"app": "test"},
+					},
+					TopologyKey: "kubernetes.io/hostname",
+				},
+			},
+		},
+	}
+	aff2 := &v1.Affinity{
+		PodAntiAffinity: &v1.PodAntiAffinity{
+			RequiredDuringSchedulingIgnoredDuringExecution: []v1.PodAffinityTerm{
+				{
+					LabelSelector: &metav1.LabelSelector{
+						MatchLabels: map[string]string{"app": "test"},
+					},
+					TopologyKey: "kubernetes.io/hostname",
+				},
+			},
+		},
+	}
+
+	assert.True(t, affinityEqual(nil, nil))
+	assert.False(t, affinityEqual(aff1, nil))
+	assert.False(t, affinityEqual(nil, aff1))
+	assert.True(t, affinityEqual(aff1, aff2))
+}