django-multitenant

Python/Django support for distributed multi-tenant databases like Postgres+Citus

Enables easy scale-out by adding the tenant context to your queries, enabling the database (e.g. Citus) to efficiently route queries to the right database node.

There are architecures for building multi-tenant databases viz. Create one database per tenant, Create one schema per tenant and Have all tenants share the same table(s). This library is based on the 3rd design i.e Have all tenants share the same table(s), it assumes that all the tenant relates models/tables have a tenant_id column for represnting a tenant.

The following link talks more about the trade-offs on when and how to choose the right architecture for your multi-tenat database:

https://www.citusdata.com/blog/2016/10/03/designing-your-saas-database-for-high-scalability/

Other useful links on multi-tenancy:

1. https://www.citusdata.com/blog/2017/03/09/multi-tenant-sharding-tutorial/
2. https://www.citusdata.com/blog/2017/06/02/scaling-complex-sql-transactions/

Installation:

1. pip install django_multitenant

Supported Django versions/Pre-requisites.

Tested with django 1.10 or higher.

Usage:

1. In whichever files you want to use the library import it by just saying import django_multitenant

2. All models should inherit the TenantModel class. Ex: class Product(TenantModel):

3. Define a static variable named tenant_id and specify the tenant column using this variable. Ex: tenant_id='store_id'

4. A sample model implementing the above 2 steps:

    class Product(TenantModel):
    	store = models.ForeignKey(Store)
    	tenant_id='store_id'
    	name = models.CharField(max_length=255)
    	description = models.TextField()
    	class Meta(object):
    		unique_together = ["id", "store"]

5. In an application function set the tenant using set_current_tenant(t) api. This would scope all the django API calls automatically(without specifying explicit filters) to a single tenant. If the current_tenant is not set, then the default/native API without tenant scoping is used.

    def application_function:
    	# current_tenant can be stored as a SESSION variable when a user logs in.
    	# This should be done by the app
    	t = current_tenant
    	#set the tenant
    	set_current_tenant(t);
    	#Django ORM API calls;
    	#Command 1;
    	#Command 2;
   		#Command 3;
    	#Command 4;
   		#Command 5;

Supported APIs:

1. Most of the APIs under Model.objects.* except select_related().
2. Model.save() injects tenant_id for tenant inherited models.

   s=Store.objects.all()[0]
   set_current_tenant(s)
   
   #All the below API calls would add suitable tenant filters.
   #Simple get_queryset()
   Product.objects.get_queryset()
   
   #Simple join
   Purchase.objects.filter(id=1).filter(store__name='sai').filter(product__description='')
   
   #Update
   Purchase.objects.filter(id=1).update(id=1)
   
   #Save
   p=Product(8,1,'sai','hello')
   p.save()
   
   #Simple aggregates
   Product.objects.count()
   Product.objects.filter(store__name='sai').count()
   Product.objects.filter(name='sai').aggregate(Avg('store_id'))
   
   #Subqueries
   Product.objects.filter(name='sai');
   Purchase.objects.filter(product__in=p);

Credits

This library uses similar logic of setting/getting tenant object as in django-simple-multitenant. We thank the authors for their efforts.