Add Prometheus alert for API availability

Change-Id: I6ed2707d19c3d475741affb94940628c6c76b4c5
diff --git a/keystone/meta/prometheus.yml b/keystone/meta/prometheus.yml
new file mode 100644
index 0000000..24186df
--- /dev/null
+++ b/keystone/meta/prometheus.yml
@@ -0,0 +1,18 @@
+{%- if pillar.keystone.server is defined and pillar.keystone.server.get('enabled') %}
+{% raw %}
+server:
+  alert:
+    KeystoneAPIDown:
+      if: >-
+        max(openstack_api_check_status{service=~"keystone.+"}) by (service) == 0
+      for: 2m
+      labels:
+        severity: down
+        service: "{{ $labels.service }}"
+      annotations:
+        summary: "Endpoint check for '{{ $labels.service}}' is down"
+        description: >-
+            Endpoint check for '{{ $labels.service}}' is down for 2 minutes
+{% endraw %}
+{%- endif %}
+
diff --git a/metadata/service/support.yml b/metadata/service/support.yml
index 25c2402..413387b 100644
--- a/metadata/service/support.yml
+++ b/metadata/service/support.yml
@@ -15,3 +15,5 @@
         enabled: true
       telegraf:
         enabled: true
+      prometheus:
+        enabled: true