dependency-injector-tenant-singleton

Tenant-scoped singleton provider for the dependency-injector framework.

Overview

TenantSingleton is a provider that creates singleton instances scoped to individual tenants. Unlike a global singleton that returns the same instance everywhere, TenantSingleton returns the same instance for the same tenant while providing different instances for different tenants.

This is useful in multi-tenant applications where you need:

• Separate configurations per tenant
• Isolated resources for each tenant
• Tenant-scoped caching or state

Installation

pip install dependency-injector-tenant-singleton

Usage

from dependency_injector import containers, providers
from dependency_injector_tenant_singleton import TenantSingleton


def get_current_tenant() -> str:
    """Get the current tenant identifier."""
    return "tenant-a"


class Container(containers.DeclarativeContainer):
    #: Current active tenant
    active_tenant = providers.Factory(get_current_tenant)

    #: Tenant-scoped service instance
    service = TenantSingleton(
        active_tenant,
        SomeService,
        # Additional args/kwargs are passed to the factory
    )


container = Container()

# Same tenant - same instance
with container.active_tenant.override("tenant-a"):
    instance1 = container.service()
    instance2 = container.service()
    assert instance1 is instance2  # Same instance for tenant-a

# Different tenant - different instance
with container.active_tenant.override("tenant-b"):
    instance3 = container.service()
    assert instance3 is not instance1  # Different instance for tenant-b

# Back to tenant-a - same instance as before
with container.active_tenant.override("tenant-a"):
    instance4 = container.service()
    assert instance4 is instance1  # Same instance again

How It Works

TenantSingleton accepts a provider that returns a tenant identifier and a factory callable:

TenantSingleton(tenant_provider, factory, *args, **kwargs)

• tenant_provider - A provider that returns the current tenant identifier
• factory - Callable that creates the instance (class, function, etc.)
• *args, **kwargs - Additional arguments passed to the factory

Internally, TenantSingleton maintains a mapping of tenant identifiers to singleton instances. When called, it:

1. Resolves the current tenant identifier from tenant_provider
2. Creates a singleton for that tenant if it doesn't exist
3. Returns the tenant's singleton instance

License

MIT License