Multi-site projects on Divio

Multi-site hosting, also known as multi-tenancy, makes it possible to host multiple sites, serving multiple domains, using a single database.

Note

This is distinct from serving a single site under multiple domains - this does not require django-multisite, and only requires those domains to be set up in the Control Panel.

We support two multi-site options:

• using our Mirrors feature, with multiple projects running the same codebase and using the same content (recommended)

• (for Django sites only) a DIY implementation via the django CMS Multisite package

Using Mirrors

Multiple “mirror” projects can be launched as duplicates of an original. They will all share exactly the same codebase. By default, each mirror is an independent project, with its own database and media storage. In a multi-site arrangement, all the mirrors will share a single database and media storage.

Commits to the base project codebase can be rolled out automatically or manually across all the mirrors.

Advantages

This arrangement has numerous benefits. It brings better sub-site isolation; a problem with one site’s performance will not affect other sites. It also offers better permission management, and better scalability of many small applications across multiple hosts.

Per-site resources can be fine-tuned more effectively (though overall resource usage may be slightly higher).

Caveats

To achieve zero downtime deployments a good policy of maintaining backwards-compatible database migrations is required, as the first project in the mirrored groups to be deployed with the fresh code will apply any database migrations; these will affect all projects. They therefore need to be backwards-compatible, so that others will continue to work with the new database schema. Subsequent code updates, applied once all projects in the group have been deployed, will no longer need to support the old schema.

DIY implementation (for Django sites only)

This option is still available, but is no longer recommended.

You will need to install django CMS Multisite package and manage any settings and configuration manually.

We are able to assist by setting up your Test server domains, but other than that we are not able to provide support for this option.

Logging in to multi-site instances

In all multi-site projects, you will notice that each site requires its own log-in. Logging in to one will not log you in to another. This is because the Django session cookie is per-domain.

Switching between sites in a local multi-site project

Suppose you have a multi-site project example-stage.eu.aldryn.io whose domains are configured thus:

Site	Live	Test
Germany	example.de	de.example-stage.eu.aldryn.io
Ghana	example.gh	gh.example-stage.eu.aldryn.io
USA	example.us	us.example-stage.eu.aldryn.io

On both the Test and Live Cloud servers, domain routing will be configured automatically.

Locally, more work is required, as each of the sites will be served at the same address (i.e. localhost). Unlike the Cloud set-up, your local environment has no way to route different requests to different sites - because the request for localhost doesn’t contain the domain information needed to do this.

Instead, you will need to handle multi-site routing manually.

There are two approaches you can take:

Option one: Force the site with an environment variable

This is the simpler method and recommended unless you need to be able to switch often between sites.

Set a local environment variable, SITE_ID, to force serving of a particular site. The site ID you need can be found in the list of Sites in the admin.

After changing the SITE_ID you may need to restart the local server for the change to take effect.

If you set explicitly set the SITE_ID this way, the next method will not work.

Option two: capture the sites’ domains in /etc/hosts

The other method is to point all the domains you need to handle locally to localhost. For example, for each of the domains in the table above, you could add an entry in your /etc/hosts file:

localhost   example.de
localhost   example.gh
localhost   example.us

These should match the domains as they appear in the admin at Sites > Sites.

Now, each domain will resolve to localhost.

It will help to have your local site served on port 80, so in the docker-compose file, set:

ports:
 - "80:80"

for the web service.

The local Divio environment server running will now be able to use the information contained in the request for say example.de or example.gh to serve the required site.

Using this method, you can readily switch between sites using the standard site-switching functionality. The site-switching links will refer to the various Live sites, but these addresses will be intercepted by the modified hosts file.

Note

If the port on which you access local sites is not 80, you will need to append this to the addresses you require.

This method is more convenient if your local development work requires you to switch sites, but you must remember to remove the entries from hosts once you’ve finished.

Note also that if you force the site using the environment variable method, then this method will not work.