Fail fast without ActiveRecord connection

lib/gitlab/cluster/mixins/puma_cluster.rb

@@ -6,6 +6,7 @@ module Gitlab
       module PumaCluster
         def self.prepended(base)
           raise 'missing method Puma::Cluster#stop_workers' unless base.method_defined?(:stop_workers)
+          raise 'ActiveRecord connection not established. Unable to start.' unless ActiveRecord::Base.connected?
         end
 
         # This looks at internal status of `Puma::Cluster`

lib/gitlab/cluster/mixins/unicorn_http_server.rb

@@ -8,6 +8,8 @@ module Gitlab
           unless base.method_defined?(:reexec) && base.method_defined?(:stop)
             raise 'missing method Unicorn::HttpServer#reexec or Unicorn::HttpServer#stop'
           end
+
+          raise 'ActiveRecord connection not established. Unable to start.' unless ::ActiveRecord::Base.connected?
         end
 
         def reexec