Add Prometheus alerts

Change-Id: I6ebbebcf754db7aec82d3ee4ae87034d9ef267d4
diff --git a/metadata/service/support.yml b/metadata/service/support.yml
index 7b64df5..1bab20d 100644
--- a/metadata/service/support.yml
+++ b/metadata/service/support.yml
@@ -9,3 +9,5 @@
         enabled: false
       sphinx:
         enabled: false
+      prometheus:
+        enabled: true
\ No newline at end of file
diff --git a/ntp/meta/prometheus.yml b/ntp/meta/prometheus.yml
new file mode 100644
index 0000000..0428dab
--- /dev/null
+++ b/ntp/meta/prometheus.yml
@@ -0,0 +1,17 @@
+{%- from "ntp/map.jinja" import client with context %}
+
+{%- if client.get('enabled', False) %}
+{%- raw %}
+server:
+  alert:
+    NtpOffset:
+      if: >-
+        ntpq_offset >= 250
+      labels:
+        severity: warning
+        service: ntp
+      annotations:
+        summary: 'NTP offset is too high'
+        description: 'NTP offset is higher than 250ms on node {{ $labels.host }}'
+{%- endraw %}
+{%- endif %}
\ No newline at end of file