django-multisite-plus

An extension to django-multisite and djangocms-multisite that brings:

• Packaging as an Addon for Divio Cloud and configuration of django-multisite and djangocms-multisite
• Tools to help handling moving database dumps between environments (live/stage/test/local) and still maintaining sensible domain names.
• single-process and multi-process deployment options

Installation on Divio Cloud

Install the Addon. To be able to use the multisite setup locally, define the DJANGO_MULTISITE_PLUS_REWRITE_DOMAIN_FORMAT environment variable (and/or set a value in the configuration form as a default).

DJANGO_MULTISITE_PLUS_REWRITE_DOMAIN_FORMAT='{}.192.168.99.100.xip.io'

This controls how you'll access the various sites. {} will be replaced with the site slug. In the example above we're using xip.io a service that returns the ip in the name for any domain following that format. Alternatively you could create an entry in /etc/hosts for every domain you want to support and point it to your local ip. Or have a local proxy that handles name resolution.

The DJANGO_MULTISITE_PLUS_REWRITE_DOMAINS environment variable controls whether the domain names are re-written based on DJANGO_MULTISITE_PLUS_REWRITE_DOMAIN_FORMAT on every app startup. Set it to True for local development and test servers. On the live server, when the real_domain should be used, set DJANGO_MULTISITE_PLUS_USE_REAL_DOMAIN to True.

Now either create multiple Site entries (in admin under "Multisite+") and set the slug and real domain accordingly (real domain can be blank). Or set the DJANGO_MULTISITE_PLUS_SITES in settings.py like this and make sure DJANGO_MULTISITE_PLUS_AUTO_POPULATE_SITES is True:

DJANGO_MULTISITE_PLUS_SITES = {
    'portal': {
        'id': 1,
        'real_domain': 'www.example.com',
        'name': 'Example Portal',
    },
    'site1': {
        'id': 2,
        'real_domain': 'www.site1.com',
        'name': 'Site 1',
    },
    'site2': {
        'id': 3,
        'real_domain': 'www.site2.com',
        'name': 'Site 2',
    },
}

id is the django.contrib.sites.Site.id and is optional. If left out the slug (the key in the dict) will be used to create or update the existing database entries. If present the site with the given id will be updated or created.

single-process vs multi-process

DJANGO_MULTISITE_PLUS_MODE can be either single-process or multi-process.

single-process means that only one python process will be run, which will serve all domains. This makes requests slower (~400ms) because of some reloading that needs to be done, but is much easier to deploy and does not use much resources (ram). To accomplish this it uses the dynamic SITE_ID and monkeypatches that come with django-multisite.

multi-process means that there will be a process per SITE_ID. The setup uses a combination of uwsgi emperor mode (by reading domains directly from the postgres database from django.contrib.sites.Site) and uwsgi fastrouter to route incoming requests to the correct process. With the multi-process approach requests can be served faster, but it uses much more ram (multiplied by the amount of sites).

required uwsgi plugins

The multi-process mode requires the emperor_pg uwsgi plugin. It is cumbersome to compile a custom version of uwsgi with this plugin, so we build the default uwsgi wheel on the divio cloud with support already in there. At the time of writing alpine is not supported yet. If this stops working, ask a Divio Cloud SRE to update https://wheels.aldryn.net/admin/wheelsproxy/package/59573/change/ . This is the setup command we run on the wheels proxy before building the uwsgi wheel:

echo '[uwsgi]\nmain_plugin=python,gevent,emperor_pg\ninherit = base' >/tmp/profile.ini && export UWSGI_PROFILE=/tmp/profile.ini

avoid slow requests on new workers

uwsgi will sometimes restart workers and start new workers on-the-fly. The first request to a django process is really slow though, because django loads the bulk of its code at that time. This can produce slow requests at random times. To avoid this we can load the bulk of the django app already at wsgi init time. Replace wsgi.py with the following:

import os
from aldryn_django import startup

application = startup.wsgi(path=os.path.dirname(__file__))

# Django loads most of its code when the first request comes in. But that
# means that the first request of a new worker will always be really
# slow. So we simulate a request here to warm the process up.
try:
    from django.test.client import Client
    client = Client()
    response = client.get('/', follow=True)
    print('Process warmed up with initial request.')
except Exception as exc:
    print('Failed to warm up process with initial request.')

Multi-process tips

Adding extra params to the vassals on a domain-level

Now the model can carry additional configurations to be used on vassal/socket INI file. For example, one change the number of workers for a given by simply:

from django_multisite_plus.models import Site
site = Site.objects.get(id=XXXXX)
site.extra_uwsgi_ini = '''
workers = 5
'''
site.save()

Please note that those change will take effect only after a server restart.

Future package structure

• Some of the features of django-multisite-plus may be worth merging into django-multisite.
• The configuration of djangocms-multisite could be moved to a separate Addon so this package does not need to depend on django-cms.