Auto-configure WSGI worker processes

Automatically configure WSGI worker processes inline with other
charms using the worker-multiplier configuration option and the
WSGI worker configuration context from charm-helpers.

Change-Id: Ib8af4a5a54fcff13a05ba4f4094bf123d5282c4a

config.yaml

@@ -348,3 +348,12 @@ options:
       .
       If not provided, leave the option unconfigured which enables all of the
       above.
+  worker-multiplier:
+    type: float
+    default:
+    description: |
+      The CPU core multiplier to use when configuring worker processes for
+      Horizon. By default, the number of workers for each daemon is set to
+      twice the number of CPU cores a service unit has. When deployed in
+      a LXD container, this default value will be capped to 4 workers
+      unless this configuration option is set.

hooks/horizon_utils.py

@@ -98,12 +98,14 @@ CONFIG_FILES = OrderedDict([
     }),
     (APACHE_CONF, {
         'hook_contexts': [horizon_contexts.HorizonContext(),
-                          context.SyslogContext()],
+                          context.SyslogContext(),
+                          context.WSGIWorkerConfigContext()],
         'services': ['apache2', 'memcached'],
     }),
     (APACHE_24_CONF, {
         'hook_contexts': [horizon_contexts.HorizonContext(),
-                          context.SyslogContext()],
+                          context.SyslogContext(),
+                          context.WSGIWorkerConfigContext()],
         'services': ['apache2', 'memcached'],
     }),
     (APACHE_SSL, {

templates/icehouse/openstack-dashboard.conf

@@ -1,5 +1,5 @@
 WSGIScriptAlias {{ webroot }} /usr/share/openstack-dashboard/openstack_dashboard/wsgi/django.wsgi
-WSGIDaemonProcess horizon user=horizon group=horizon processes=3 threads=10
+WSGIDaemonProcess horizon user=horizon group=horizon processes={{ processes }} threads=10
 WSGIProcessGroup horizon
 Alias /static /usr/share/openstack-dashboard/openstack_dashboard/static/
 Alias /horizon/static /usr/share/openstack-dashboard/openstack_dashboard/static/

templates/newton/openstack-dashboard.conf

@@ -1,5 +1,5 @@
 WSGIScriptAlias {{ webroot }} /usr/share/openstack-dashboard/openstack_dashboard/wsgi/django.wsgi
-WSGIDaemonProcess horizon user=horizon group=horizon processes=3 threads=10
+WSGIDaemonProcess horizon user=horizon group=horizon processes={{ processes }} threads=10
 WSGIProcessGroup horizon
 Alias /static /usr/share/openstack-dashboard/openstack_dashboard/static/
 Alias /horizon/static /usr/share/openstack-dashboard/openstack_dashboard/static/

templates/ocata/openstack-dashboard.conf

@@ -1,5 +1,5 @@
 WSGIScriptAlias {{ webroot }} /usr/share/openstack-dashboard/openstack_dashboard/wsgi/django.wsgi
-WSGIDaemonProcess horizon user=www-data group=www-data processes=3 threads=10
+WSGIDaemonProcess horizon user=www-data group=www-data processes={{ processes }} threads=10
 WSGIProcessGroup horizon
 Alias /static /var/lib/openstack-dashboard/static/
 Alias /horizon/static /var/lib/openstack-dashboard/static/

templates/pike/openstack-dashboard.conf

@@ -1,5 +1,5 @@
 WSGIScriptAlias {{ webroot }} /usr/share/openstack-dashboard/openstack_dashboard/wsgi/django.wsgi
-WSGIDaemonProcess horizon user=horizon group=horizon processes=3 threads=10
+WSGIDaemonProcess horizon user=horizon group=horizon processes={{ processes }} threads=10
 WSGIProcessGroup horizon
 Alias /static /var/lib/openstack-dashboard/static/
 Alias /horizon/static /var/lib/openstack-dashboard/static/