django-pgschemas 0.1.2

Schemas

This app uses PostgreSQL schemas to support data multi-tenancy in a single Django project. For an accurate description on schemas, see the official documentation on PostgreSQL schemas.

The terms schema and tenant are used indistinctly all over the documentation. However, it is important to note some subtle differences between the two. We consider a tenant to be a subset of data that can be accessed with a URL (routed), and we use database schemas for that purpose. Still, there can be schemas that shouldn’t be considered tenants according to our definition. One good example is the public schema, which contains data shared across all tenants. That said, remember that every tenant is a schema, but not every schema is a tenant.

Usage

Use django_pgschemas.postgresql_backend as your database engine.

DATABASES = {
    "default": {
        "ENGINE": "django_pgschemas.postgresql_backend",
        # ...
    }
}

Add the middleware django_pgschemas.middleware.TenantMiddleware to the top of MIDDLEWARE, so that each request can be set to use the correct schema.

MIDDLEWARE = (
    "django_pgschemas.middleware.TenantMainMiddleware",
    #...
)

Add django_pgschemas.routers.SyncRouter to your DATABASE_ROUTERS, so that the correct apps can be synced, depending on the target schema.

DATABASE_ROUTERS = (
    "django_pgschemas.routers.SyncRouter",
    #...
)

Add the minimal tenant configuration.

TENANTS = {
    "public": {
        "APPS": [
            "django.contrib.contenttypes",
            "django.contrib.staticfiles",
            # ...
            "django_pgschemas",
            "shared_app",
            # ...
        ],
        "TENANT_MODEL": "shared_app.Client",
        "DOMAIN_MODEL": "shared_app.Domain",
    },
    # ...
    "default": {
        "APPS": [
            "django.contrib.auth",
            "django.contrib.sessions",
            # ...
            "tenant_app",
            # ...
        ],
        "URLCONF": "tenant_app.urls",
    }
}

Each entry in the TENANTS dictionary represents a static tenant, except for default, which controls the settings for dynamic tenants (that is, database controlled). public is always treated as shared schema and cannot be routed directly.

More static tenants can be added and routed.

TENANTS = {
    # ...
    "www": {
        "APPS": [
            "django.contrib.auth",
            "django.contrib.sessions",
            # ...
            "main_app",
        ],
        "DOMAINS": ["mydomain.com"],
        "URLCONF": "main_app.urls",
    },
    "blog": {
        "APPS": [
            "django.contrib.auth",
            "django.contrib.sessions",
            # ...
            "blog_app",
        ],
        "DOMAINS": ["blog.mydomain.com", "help.mydomain.com"],
        "URLCONF": "blog_app.urls",
    },
    # ...
}

For Django to function properly, INSTALLED_APPS and ROOT_URLCONF settings must be defined. Just make them get their information from the TENANTS dictionary, for the sake of consistency.

INSTALLED_APPS = []
for schema in TENANTS:
    INSTALLED_APPS += [app for app in TENANTS[schema]["APPS"] if app not in INSTALLED_APPS]

ROOT_URLCONF = TENANTS["default"]["URLCONF"]

Dynamic tenants need to be created through instances of TENANTS["public"]["TENANT_MODEL"].

# shared_app/models.py

from django.db import models
from django_pgschemas.models import TenantMixin, DomainMixin

class Client(TenantMixin):
    name = models.CharField(max_length=100)
    paid_until =  models.DateField(blank=True, null=True)
    on_trial = models.BooleanField(default=True)
    created_on = models.DateField(auto_now_add=True)

class Domain(DomainMixin):
    pass

Sync the public schema, in order to get Client model created. Also sync static schemas either one by one or using the :static: wildcard.

python manage.py migrateschema -s public
python manage.py migrateschema -s :static:

Create the first dynamic tenant.

>>> from shared_app.models import Client, Domain
>>> client1 = Client.objects.create(schema_name="client1")
>>> Domain.objects.create(domain="client1.mydomain.com", tenant=client1, is_primary=True)

Now any request made to client1.mydomain.com will automatically set PostgreSQL’s search_path to client1 and public, making shared apps available too. Also, any request to blog.mydomain.com or help.mydomain.com will set search_path to blog and public. This means that any call to the methods filter, get, save, delete or any other function involving a database connection will now be done at the correct schema, be it static or dynamic.

Management commands

Management commands provided by Django or any 3rd party app will run by default on the public schema. To run a command on a specific tenant, you can use the provided command runschema.

python manage.py runschema shell -s tenant1
python manage.py runschema loaddata tenant_app.Products -s :dynamic:

We provide a custom migrateschema command (also aliased as migrate) that is capable of running migrations on specific schemas.

# all schemas
python manage.py migrate

# static schemas only
python manage.py migrate -s :static:

# dynamic schemas only
python manage.py migrate -s :dynamic:

# specific schema by exact schema name
python manage.py migrate -s tenant1

# specific schema by partially matched domain (startswith)
python manage.py migrate -s help.mydomain

Gotchas

• It is enforced that django.contrib.contenttypes should live in the public schema. This is to guarantee that content types from all apps/tenants are stored in a single place.

• It is enforced that django.contrib.sessions can only live in schemas where the app that defines the user model also lives. The user app is django.contrib.auth by default, but could be changed via AUTH_USER_MODEL setting. This is to guarantee that session information is not leaked across tenants that do not share the same user base.

Credits

This project stands on the shoulders of giants.

• Tom Turner with django-tenants.

• Bernardo Pires with django-tenant-schemas.

• Vlada Macek with django-schemata.