supervisord: Improve memory footprint for small servers.

This cuts the number of uwsgi and message_sender works for smaller
servers with only 2GB of RAM.

puppet/zulip/manifests/app_frontend_base.pp

@@ -63,6 +63,15 @@ class zulip::app_frontend_base {
   # RAM; we just auto-detect based on available system RAM.
   $queues_multiprocess = $::memorysize_mb > 3500
   $queues = $zulip::base::normal_queues
+  if $queues_multiprocess {
+    $message_sender_default_processes = 4
+    $uwsgi_default_processes = 6
+  } else {
+    $message_sender_default_processes = 2
+    $uwsgi_default_processes = 4
+  }
+  $message_sender_processes = zulipconf("application_server", "message_sender_processes",
+                                        $message_sender_default_processes)
   file { "/etc/supervisor/conf.d/zulip.conf":
     require => Package[supervisor],
     ensure => file,
@@ -73,7 +82,8 @@ class zulip::app_frontend_base {
     notify => Service["supervisor"],
   }
 
-  $uwsgi_processes = zulipconf("application_server", "uwsgi_processes", "5")
+  $uwsgi_processes = zulipconf("application_server", "uwsgi_processes",
+                               $uwsgi_default_processes)
   file { "/etc/zulip/uwsgi.ini":
     require => Package[supervisor],
     ensure => file,

puppet/zulip/templates/supervisor/zulip.conf.template.erb

@@ -97,7 +97,7 @@ stdout_logfile=/var/log/zulip/events_message_sender.log         ; stdout log pat
 stdout_logfile_maxbytes=20MB   ; max # logfile bytes b4 rotation (default 50MB)
 stdout_logfile_backups=5     ; # of stdout logfile backups (default 10)
 directory=/home/zulip/deployments/current/
-numprocs=5
+numprocs=<%= @message_sender_processes %>
 
 ; The below sample group section shows all possible group values,
 ; create one or more 'real' group: sections to create "heterogeneous"