From 847d66cfe3b2e1895bc93a158ccccc80e6323e63 Mon Sep 17 00:00:00 2001
From: Paul Gier <pgier@redhat.com>
Date: Thu, 12 Mar 2020 16:01:49 -0500
Subject: [PATCH] pkg/alertmanager: mergepatch alertmanager containers

Instead of just appending user defined containers to the alertmanager
pods, use k8sutil.MergePatchContainers so that the default containers
can be modified.
---
 pkg/alertmanager/statefulset.go | 99 ++++++++++++++++++---------------
 1 file changed, 53 insertions(+), 46 deletions(-)

diff --git a/pkg/alertmanager/statefulset.go b/pkg/alertmanager/statefulset.go
index 1429f13c9e..34ebbe4a59 100644
--- a/pkg/alertmanager/statefulset.go
+++ b/pkg/alertmanager/statefulset.go
@@ -468,7 +468,53 @@ func makeStatefulSetSpec(a *monitoringv1.Alertmanager, config Config) (*appsv1.S
 	terminationGracePeriod := int64(120)
 	finalLabels := config.Labels.Merge(podLabels)
 
-	// PodManagementPolicy is set to Parallel to mitigate issues in kuberentes: https://github.com/kubernetes/kubernetes/issues/60164
+	defaultContainers := []v1.Container{
+		{
+			Args:           amArgs,
+			Name:           "alertmanager",
+			Image:          image,
+			Ports:          ports,
+			VolumeMounts:   amVolumeMounts,
+			LivenessProbe:  livenessProbe,
+			ReadinessProbe: readinessProbe,
+			Resources:      a.Spec.Resources,
+			Env: []v1.EnvVar{
+				{
+					// Necessary for '--cluster.listen-address' flag
+					Name: "POD_IP",
+					ValueFrom: &v1.EnvVarSource{
+						FieldRef: &v1.ObjectFieldSelector{
+							FieldPath: "status.podIP",
+						},
+					},
+				},
+			},
+			TerminationMessagePolicy: v1.TerminationMessageFallbackToLogsOnError,
+		}, {
+			Name:  "config-reloader",
+			Image: config.ConfigReloaderImage,
+			Args: []string{
+				fmt.Sprintf("-webhook-url=%s", localReloadURL),
+				fmt.Sprintf("-volume-dir=%s", alertmanagerConfDir),
+			},
+			VolumeMounts: []v1.VolumeMount{
+				{
+					Name:      "config-volume",
+					ReadOnly:  true,
+					MountPath: alertmanagerConfDir,
+				},
+			},
+			Resources:                resources,
+			TerminationMessagePolicy: v1.TerminationMessageFallbackToLogsOnError,
+		},
+	}
+
+	containers, err := k8sutil.MergePatchContainers(defaultContainers, a.Spec.Containers)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to merge containers spec")
+	}
+
+	// PodManagementPolicy is set to Parallel to mitigate issues in kubernetes: https://github.com/kubernetes/kubernetes/issues/60164
 	// This is also mentioned as one of limitations of StatefulSets: https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/#limitations
 	return &appsv1.StatefulSetSpec{
 		ServiceName:         governingServiceName,
@@ -490,51 +536,12 @@ func makeStatefulSetSpec(a *monitoringv1.Alertmanager, config Config) (*appsv1.S
 				PriorityClassName:             a.Spec.PriorityClassName,
 				TerminationGracePeriodSeconds: &terminationGracePeriod,
 				InitContainers:                a.Spec.InitContainers,
-				Containers: append([]v1.Container{
-					{
-						Args:           amArgs,
-						Name:           "alertmanager",
-						Image:          image,
-						Ports:          ports,
-						VolumeMounts:   amVolumeMounts,
-						LivenessProbe:  livenessProbe,
-						ReadinessProbe: readinessProbe,
-						Resources:      a.Spec.Resources,
-						Env: []v1.EnvVar{
-							{
-								// Necessary for '--cluster.listen-address' flag
-								Name: "POD_IP",
-								ValueFrom: &v1.EnvVarSource{
-									FieldRef: &v1.ObjectFieldSelector{
-										FieldPath: "status.podIP",
-									},
-								},
-							},
-						},
-						TerminationMessagePolicy: v1.TerminationMessageFallbackToLogsOnError,
-					}, {
-						Name:  "config-reloader",
-						Image: config.ConfigReloaderImage,
-						Args: []string{
-							fmt.Sprintf("-webhook-url=%s", localReloadURL),
-							fmt.Sprintf("-volume-dir=%s", alertmanagerConfDir),
-						},
-						VolumeMounts: []v1.VolumeMount{
-							{
-								Name:      "config-volume",
-								ReadOnly:  true,
-								MountPath: alertmanagerConfDir,
-							},
-						},
-						Resources:                resources,
-						TerminationMessagePolicy: v1.TerminationMessageFallbackToLogsOnError,
-					},
-				}, a.Spec.Containers...),
-				Volumes:            volumes,
-				ServiceAccountName: a.Spec.ServiceAccountName,
-				SecurityContext:    securityContext,
-				Tolerations:        a.Spec.Tolerations,
-				Affinity:           a.Spec.Affinity,
+				Containers:                    containers,
+				Volumes:                       volumes,
+				ServiceAccountName:            a.Spec.ServiceAccountName,
+				SecurityContext:               securityContext,
+				Tolerations:                   a.Spec.Tolerations,
+				Affinity:                      a.Spec.Affinity,
 			},
 		},
 	}, nil