Add Prometheus alert

Change-Id: Iff95c5a9c8fd2980ebf85a7db76e036bf1208ccc
diff --git a/metadata/service/support.yml b/metadata/service/support.yml
index 8e0ef24..23f1bcc 100644
--- a/metadata/service/support.yml
+++ b/metadata/service/support.yml
@@ -11,3 +11,5 @@
         enabled: true
       grafana:
         enabled: true
+      prometheus:
+        enabled: true
\ No newline at end of file
diff --git a/nginx/meta/prometheus.yml b/nginx/meta/prometheus.yml
new file mode 100644
index 0000000..11e832c
--- /dev/null
+++ b/nginx/meta/prometheus.yml
@@ -0,0 +1,16 @@
+{%- from "nginx/map.jinja" import server with context %}
+{%- if server.get('enabled', False) %}
+{%- raw %}
+server:
+  alert:
+    NginxDown:
+      if: >-
+        nginx_up != 1
+      labels:
+        severity: warning
+        service: nginx
+      annotations:
+        summary: 'Nginx service down'
+        description: 'Nginx service is down on node {{ $labels.host }}'
+{%- endraw %}
+{%- endif %}
\ No newline at end of file