Multi-Tenancy in NJS

Introduction to Multi-Tenancy

• Single-Tenant Application:

  • Each customer has a dedicated instance of the application.
  • High cost and maintenance (e.g., 100 customers = 100 instances).

• Multi-Tenant Application:

  • One instance serves multiple tenants (organizations or companies).
  • Shared resources lead to cost savings in maintenance.

Implementation of Multi-Tenant Applications

• SaaS (Software as a Service):

  • Multi-tenancy structure is primarily used for SaaS applications.

• Database Structure:

  • Not necessary to have a dedicated database for every tenant.
  • Example approaches:
    • Dedicated Database per Tenant:
      • Each tenant has its own database (e.g., tenant_ABC, tenant_XYZ).
    • Single Database for All Tenants:
      • One database with records having a tenant ID to filter data per tenant.

Challenges in Multi-Tenant Applications

• Connecting to the correct database based on the tenant making the request.
• Implementing multi-tenancy in NJS with MongoDB:
  • Use a Master Database as a control center holding tenant metadata.
  • Example collections in master database:
    • Tenants collection (tenant ID, company name, etc.).
    • Subscriptions and shared settings.

Coding Example: Setting Up Multi-Tenant Structure

• Boilerplate Code Explanation:

  • Configuring the application with necessary modules.
  • Using the Mongoose module for database connections.

• Folder Structure:

  • Organized into config, middlewares, products, tenants, and providers.

Products and Tenants Modules

• Product Module:

  • Contains product schema (fields: name, description, price).

• Tenants Module:

  • Contains tenant schema (fields: company name, tenant ID).
  • Each tenant database has its own product collection.

Middleware and Tenant ID Handling

• Middleware checks for tenant ID in request headers:
  • If tenant ID is missing, throw a bad request error.
  • If tenant ID is valid, attach it to the request for later access.

Database Connection Logic

• Use a method to retrieve the correct database connection based on the tenant ID:
  • Example: getTenantConnection(tenantID) switches the connection to the specific tenant database.

Custom Providers and Dependency Injection

• Creating a custom provider to manage tenant connections efficiently:
  • Registering providers to return appropriate models based on tenant IDs.
  • Use request-scoped providers for tenant connections.

Summary

• Single vs Multi-Tenant:
  • Single-tenancy requires multiple instances; multi-tenancy is cost-effective with shared resources.
• Connection Handling:
  • Use request headers for tenant ID; implement middleware for validation.
  • Create custom providers for managing connections and models based on tenant ID.

Conclusion

• The video covered multi-tenancy implementation in NJS with MongoDB, focusing on efficient database connections and model retrieval based on tenant requests.