Building a multitenant application with Django, a tutorial given at PyCon Nigeria 2019. This slide is based on the Django multitenant application documentation.

1. Building a Multi-tenant
Application with
Django.
Adedapo Adedamola
@dexbeulah_
Data Totems

3. Glossary
• Database – collection of structured data to model reality in a way that support
processes requiring information.
• Schema - refers to the set of formulas or “rules” imposed on data in a database to be
organized into a certain way.
• App server – is a distributed network that provides the business logic for an
application.

4. What is Multi-tenancy?
• Multi tenant applications allow you to serve multiple customers with one install of the
application.
• It is the ability to run one instance of an app, and serve it to multiple distinct end user.
Each one of them is isolated from the other in terms of performance & data-leads.

6. Iaas
• Iaas – Insfrasture Application as Software.
• This is the tenancy model created by virtualization, and it is the ability to carve
large large server into multiple virtual machine.
App 1 App 2
App 4App 3
Host OS
Hypervisor
it - centric

7. Paas
• Paas – Platform as a Service.
• This is a better way of hosting a co-habiting Apps rather than dedicating a whole
OS instance to them.
OS OS OS OS
Component

8. Saas
• Saas – Software as a Service.
• It is the ability to run a single instance of an app that serves multiple distinct end
users. Each one of them is isolated from the other in terms of performance & data-
leads.
APP 1
T 1 T 2 T 3
User
User
User
User
User
User
User
User
User

10. Saas
• Benefits:
• Reduce infrastructure costs by sharing hardware resources.
• Simplify software maintenance by keeping a single code base.
• Simplify infrastructure maintenance by having fewer nodes.
App
management
is once.
Monitoring is
once.
QA is once.

11. Multi-tenancy
• Approaches:
• Shared database with shared schema
• Shared database with isolated schema
• Isolated database with a shared app server
Argh!
Django again…

12. Crash course on Django:

13. Shared database with shared schema

14. Single-tenant app:

16. Adding multi tenancy:
• python manage.py startapp tenants
• Create a model for storing Tenant data.
• TenantAwareModel class will be subclass from.

17. Adding multi tenancy:
• Poll.model subclassing TenantAwareModel

18. Identifying tenants:
• Giving each tenant their own subdomain.
• abc.example.com
• xyz.example.com
• This will be will have a subdomain_prefix which will identify the tenant.

19. Extracting tenant from request:
• Utils.py

20. A detour to /etc/hosts:
• C:WindowsSystemsDriversetchosts

21. tenant_from_request in the views:
• Function based || Class based || Django rest framework

22. Isolating the admin:
• Get_queryset: so that only the current tenant’s objects show up.
• Save_model: so that tenant gets set on the object when the object is saved.

23. Limitation:
• Weak separation of tenant’s data.
• Tenant isolation code is intermixed with app code.
• Duplication of code.

24. QUESTION(S)?

25. Shared database with isolated schema

26. What to do?
• Map tenant to schema
• Manage database migrations
• Tenant separation in views
• A middleware to set schemas
• Add get and set methods to utils.py

27. • Mapping tenant to schema
Mapping tenants to schemas for easy routing

28. • Manage database migrations
• Tenant separation in views
• A middleware to set schemas
• Add get and set methods to utils.py
CREATE SCHEMA IF NOT EXISTS potter
SET search_path to potter
We make manage.py schema aware, therefore, it create schema according to
the tenant in case it never existed, and set search_path tenant accordingly.

29. • Tenant separation in views
• A middleware to set schemas
• Add get and set methods to utils.py
The following methods allow us to get and set the schema.

30. • Tenant separation in views
• A middleware to set schemas
Separating the tenants in the view.

31. • Tenant separation in views
• A middleware to set schemas
Separating the tenants in the view.

32. • A middleware to set schemas

33. Make admin.py aware of the shared schema
Separating the admin page for tenant.

34. Isolated database with shared app server

35. Multiple database support in Django:
To read poll from thor: Poll.objects.using(‘thor’).all()
But we’d rather avoid code duplication, therefore use db routing

36. DB_ROUTERS settings take a list of classes which implement a few methods. A router class looks like this.
DB routing:
But none takes an argument, therefore, we cannot call tenant_db_from_request
We use threadlock variables to calculate DB to use, pass it to the router

37. TO pass
Middleware class:

38. DEMO
https://youtu.be/NLhUnzvvm1s

39. Content credit:
Django Multi Tenant Application documentation.
https://books.giliq.com/projects/Django-multi-tenant/en/latest
Demo:
https://github.com/agiliq/building-multi-tenant-applications-with-django/tree/master/isolated-db
Memes credit:
Ajakaye Paul
E-mail:
dexbeulah@gmail.com

40. THANK YOU