Add constraints in job start and add .prometheus.available hint

templates/job_start

@@ -9,6 +9,7 @@
 [[- if has .nomad "priority" ]]
   priority = [[ .nomad.priority ]]
 [[- end ]]
+[[ template "common/constraints" . ]]
 
 [[- if has .nomad "update" ]]
 

variables.yml

@@ -194,8 +194,11 @@ mail:
   smtp_service_name: smtp
 
 prometheus:
+  # Set to true if prometheus is available so jobs can use it as a hint to
+  # turn metrics support on
+  available: false
   # Controls if prometheus metrics should be enabled on all tasks supporting it
-  enabled: False
+  enabled: false
   # Path of the vault PKI used for monitoring
   vault_pki: '[[ .vault.root ]]pki/monitoring'