Add topology spread constrains

Signed-off-by: Mario Fernandez <mariofer@redhat.com>

Documentation/api.md

@@ -111,6 +111,7 @@ The `AlertmanagerUserWorkloadConfig` resource defines the settings for the Alert
 | secrets | []string | Defines a list of secrets that need to be mounted into the Alertmanager. The secrets must reside within the same namespace as the Alertmanager object. They will be added as volumes named secret-<secret-name> and mounted at /etc/alertmanager/secrets/<secret-name> within the 'alertmanager' container of the Alertmanager Pods. |
 | nodeSelector | map[string]string | Defines the nodes on which the pods are scheduled. |
 | tolerations | [][v1.Toleration](https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.27/#toleration-v1-core) | Defines tolerations for the pods. |
+| topologySpreadConstraints | []v1.TopologySpreadConstraint | Defines a pod's topology spread constraints. |
 | volumeClaimTemplate | *[monv1.EmbeddedPersistentVolumeClaim](https://github.com/prometheus-operator/prometheus-operator/blob/v0.66.0/Documentation/api.md#embeddedpersistentvolumeclaim) | Defines persistent storage for Alertmanager. Use this setting to configure the persistent volume claim, including storage class, volume size and name. |
 
 [Back to TOC](#table-of-contents)

Documentation/openshiftdocs/modules/alertmanageruserworkloadconfig.adoc

@@ -32,6 +32,8 @@ Appears in: link:userworkloadconfiguration.adoc[UserWorkloadConfiguration]
 
 |tolerations|[]v1.Toleration|Defines tolerations for the pods.
 
+|topologySpreadConstraints|[]v1.TopologySpreadConstraint|Defines a pod's topology spread constraints.
+
 |volumeClaimTemplate|*monv1.EmbeddedPersistentVolumeClaim|Defines persistent storage for Alertmanager. Use this setting to configure the persistent volume claim, including storage class, volume size and name.
 
 |===

pkg/manifests/manifests.go

@@ -519,6 +519,11 @@ func (f *Factory) AlertmanagerUserWorkload(trustedCABundleCM *v1.ConfigMap) (*mo
 		a.Spec.Tolerations = alertmanagerConfig.Tolerations
 	}
 
+	if len(alertmanagerConfig.TopologySpreadConstraints) > 0 {
+		a.Spec.TopologySpreadConstraints =
+			alertmanagerConfig.TopologySpreadConstraints
+	}
+
 	for i, c := range a.Spec.Containers {
 		switch c.Name {
 		case "alertmanager-proxy", "tenancy-proxy", "kube-rbac-proxy-metric":

pkg/manifests/manifests_test.go

@@ -2824,7 +2824,20 @@ ingress:
 
 func TestAlertManagerUserWorkloadSecretsConfiguration(t *testing.T) {
 	c := NewDefaultConfig()
-	c.UserWorkloadConfiguration.Alertmanager.Secrets = []string{"test-secret", "slack-api-token"}
+	uwc, err := NewUserConfigFromString(`alertmanager:
+  topologySpreadConstraints:
+  - maxSkew: 1
+    topologyKey: type
+    whenUnsatisfiable: DoNotSchedule
+    labelSelector:
+      matchLabels:
+        foo: bar
+  secrets:
+  - test-secret
+  - slack-api-token
+  `)
+
+	c.UserWorkloadConfiguration = uwc
 
 	f := NewFactory("openshift-monitoring", "openshift-user-workload-monitoring", c, defaultInfrastructureReader(), &fakeProxyReader{}, NewAssets(assetsPath), &APIServerConfig{}, &configv1.Console{})
 	a, err := f.AlertmanagerUserWorkload(
@@ -2842,6 +2855,14 @@ func TestAlertManagerUserWorkloadSecretsConfiguration(t *testing.T) {
 	if !slices.Contains(a.Spec.Secrets, "slack-api-token") {
 		t.Fatal("Alertmanager secret `slack-api-token` is not configured correctly")
 	}
+
+	if a.Spec.TopologySpreadConstraints[0].MaxSkew != 1 {
+		t.Fatal("Alertmanager UWM spread contraints MaxSkew not configured correctly")
+	}
+
+	if a.Spec.TopologySpreadConstraints[0].WhenUnsatisfiable != "DoNotSchedule" {
+		t.Fatal("Alertmanager UWM spread contraints WhenUnsatisfiable not configured correctly")
+	}
 }
 
 func TestNodeExporter(t *testing.T) {

pkg/manifests/types.go

@@ -500,6 +500,8 @@ type AlertmanagerUserWorkloadConfig struct {
 	NodeSelector map[string]string `json:"nodeSelector,omitempty"`
 	// Defines tolerations for the pods.
 	Tolerations []v1.Toleration `json:"tolerations,omitempty"`
+	// Defines a pod's topology spread constraints.
+	TopologySpreadConstraints []v1.TopologySpreadConstraint `json:"topologySpreadConstraints,omitempty"`
 	// Defines persistent storage for Alertmanager. Use this setting to
 	// configure the persistent volume claim, including storage class,
 	// volume size and name.