Middleware for Dynamic Database URL Based on Subdomain in NestJS with Prisma

Question

I’m working on a multi-tenant application using NestJS and Prisma. I want to dynamically set the databaseUrl based on the subdomain from my Next.js frontend. For example, if the subdomain is tenant1, I want to connect to tenant1_db, and if it’s tenant2, I want to connect to tenant2_db.

I’ve created a middleware to extract the subdomain from the request, but I’m not sure how to proceed with dynamically setting the databaseUrl in Prisma. Here’s my current middleware:

import { Injectable, NestMiddleware } from '@nestjs/common';

@Injectable()
export class DynamicDbMiddleware implements NestMiddleware {
  use(req: any, res: any, next: () => void) {
    const host = req.hostname;
    const subdomain = host.split('.')[0]; // Extract the subdomain
    req['subdomain'] = subdomain; // Attach the subdomain to the request object

    next();
  }
}

myNameCoad · Accepted Answer · 2025-01-29 13:18:24Z

0

At a high level, you need to create a dynamic DB instance based on each request.

Request provider is what you are looking for

https://docs.nestjs.com/fundamentals/injection-scopes#request-provider

then you could create a database service. Something like this

@Injectable({ scope: Scope.REQUEST })
export class DatabaseProvider {
  private dbClient;

  constructor(
    @Inject(REQUEST) private readonly request: Request,
  ) {}

  getDbClient() {
    if (!this.dbClient) {
      const dbUrl = this.request.user?.dbUrl // get your subdomain or subdomain url here;
      this.dbClient = createClient(dbUrl);
    }

    return this.dbClient;
  }
}

then for any service or repository you will have to inject the DatabaseProvider and call getDbClient. With this singleton pattern each request should only create one DB client instance. Of course, your system creates new DB instance for each request which is a trade off unless you have pre-defined domains list and store their associated DB clients somewhere.

Happy coding.

answered Jan 29 at 13:18

myNameCoad

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1 Comment

Abdulaziz mohammed Jan 30 at 15:10

Thank you but my tenants are not that big i will manually store their dburls so i can stop creating new prisma clients what is the best way

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