Added some optimization to Passenger, the Rails application server.

Change-Id: I1168c4433761dd0d77634577a493cfca1c27f85c
Reviewed-on: https://review.openstack.org/23127
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Reviewed-by: Elizabeth Krumbach <lyz@princessleia.com>
Approved: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins

templates/passenger-vhost.erb

@@ -4,6 +4,19 @@ Listen <%= dashboard_port %>
   ServerName <%= name %>
   DocumentRoot <%= docroot %>
   RailsBaseURI <%= rails_base_uri %>
+
+  # Apparently HighPerformance, MaxPoolSize, PoolIdleTime and MaxRequests
+  # are all optimized by default in Passenger 3. Currently the dashboard
+  # server has the deb for libapache2-mod-passenger 2.2.11debian-2 installed
+  # PassengerMaxRequests 1000 doesn't need to be set
+  # PassengerHighPerformance on mod_rewrite might be inaccessible if on
+  # MaxPoolSize setting based on 4GB RAM with 4 cpu cores
+  # StatThrottleRate setting checks rails config changes every half hour
+  # rather than every request
+  PassengerMaxPoolSize 30
+  PassengerPoolIdleTime 1500
+  PassengerStatThrottleRate 1800
+
   <Directory <%= docroot %>>
     Options None
     AllowOverride AuthConfig