Add persistence to AlertManager

Sem-Ver: feature
Change-Id: Ic364e58f2ae94f899ce8a2fb874ac63294e14ec4
diff --git a/releasenotes/notes/add-alertmanager-persistence-0eaf7914c262bdf6.yaml b/releasenotes/notes/add-alertmanager-persistence-0eaf7914c262bdf6.yaml
new file mode 100644
index 0000000..f587c2c
--- /dev/null
+++ b/releasenotes/notes/add-alertmanager-persistence-0eaf7914c262bdf6.yaml
@@ -0,0 +1,5 @@
+---
+fixes:
+  - AlertManager did not have any persistence which meant that any silences
+    would not last through a restart of the pod.  This patch adds persistence
+    so that silences would last survive a restart of the pod.
diff --git a/roles/kube_prometheus_stack/vars/main.yml b/roles/kube_prometheus_stack/vars/main.yml
index 012b1ab..7bf0337 100644
--- a/roles/kube_prometheus_stack/vars/main.yml
+++ b/roles/kube_prometheus_stack/vars/main.yml
@@ -26,6 +26,14 @@
         - action: "labeldrop"
           regex: "^(container|endpoint|namespace|pod|service)$"
     alertmanagerSpec:
+      storage:
+        volumeClaimTemplate:
+          spec:
+            storageClassName: general
+            accessModes: ["ReadWriteOnce"]
+            resources:
+              requests:
+                storage: 40Gi
       nodeSelector:
         openstack-control-plane: enabled
   grafana: