Multi-tenant

One database per tenant, switched per request based on the active session. Your model code does not change. Queries cannot accidentally cross tenants.

How it works

When a session has an account.id, dispatch (or AuthMiddleware) calls aset_tenant(account_id) before running the handler:

• The function looks up the tenant DB connection details (cached in Redis, built from your Account / Db models on miss).
• Builds and registers a Django connection for that tenant if not already present.
• Stores the active connection name (<TENANT_DB_PREFIX>_<id>) in a ContextVar (db_state).

DBRouter reads that ContextVar on every ORM query and routes to the matching connection. Models declared as "always master" stay on the default DB.

Setup

Add the router and tenant settings:

DATABASE_ROUTERS = ['zeromcp.DBRouter']

DEFAULT_DATABASE = DATABASES['default']
TENANT_ACCOUNT_MODEL = 'core.Account'
TENANT_USER_MODEL = 'core.User'
TENANT_USER_API_MODEL = 'core.UserApi'
TENANT_DB_PREFIX = 'tenant'
HASH_LENGTH = 32

Provide a model that holds tenant connection details. Minimum shape:

class Account(models.Model):
    name = models.CharField(max_length=100)
    status_id = models.IntegerField(default=1)

class Db(models.Model):
    host = models.CharField(max_length=200)
    user = models.CharField(max_length=100)
    password = models.CharField(max_length=200)
    account = models.OneToOneField(Account, on_delete=models.CASCADE,
                                   related_name='db', null=True)

API

All exported from the top-level zeromcp package — from zeromcp import set_tenant, aset_tenant, ....

Usage

In a resource

Nothing to do. Dispatch handles it automatically when the session has an account.

In a Django management command

from zeromcp import set_tenant

class Command(BaseCommand):
    def handle(self, *args, account_id, **opts):
        set_tenant(account_id)
        # any ORM query from here on routes to the tenant DB
        User.objects.update(...)

In a Celery task

Celery tasks are typically sync — use set_tenant:

from zeromcp import set_tenant

@shared_task
def export_report(account_id):
    set_tenant(account_id)
    # any ORM query from here on routes to the tenant DB
    rows = list(Report.objects.all())
    ...

For async tasks (@shared_task with async def), use await aset_tenant(account_id).

Long-running scripts iterating over tenants

# script-only — mutates the global default connection.
# Do not call from inside an ASGI request.
from zeromcp.tenant.tenant import set_default, unset_default

for account_id in tenant_ids:
    await set_default(account_id)
    try:
        # everything inside treats this tenant as the default DB
        await run_migration_step()
    finally:
        await unset_default(account_id)

Master DB

Models that should always live on the master DB (users, accounts, billing) are configured in the router. The router uses an allow-list pattern for "always master" — typically your auth and billing apps.

Connection caching

Tenant connection dictionaries are cached in Redis under <TENANT_DB_PREFIX>:connections:<id>. The first request after a deploy hits the master DB to build it; subsequent requests read from Redis. Updating the Db row for a tenant requires invalidating that cache key.

0-mcp by Stamatios Stamou Jr — github.com/ssjunior/0-mcp