Recap

In the first part, create a Multi-tenancy Application In Nest.js – Part 1, we set up the Nest.js framework and configured and tested the microservices architecture application using Nest.js. In its second part, we used Sequelize and Mongoose to access the database and tested for both MySQL database and MongoDB.

Async Connection

In this part; we will see how to let the application connect to multiple databases depending on the request. Since it is a multi-tenancy application, each tenant has their own database containing their data accessing the same application, thus the application needs to connect to different databases. We will change the pass repository option method and use forRootAsync() instead of forRoot(), we need to use a custom class for configuration.

For both Sequelize and Mongoose, add the following:

MongooseModule.forRootAsync({
    useClass:MongooseConfigService
  }),
SequelizeModule.forRootAsync({
      useClass:SequelizeConfigService
})

We will create a config file and two classes: MongooseConfigService and SequelizeConfigService

The plan here is to add injection for each incoming request and use a domain to switch between connections.

So we need to use @Injectable({scope:Scope.REQUEST}), and on the class constructor, we use @Inject(REQUEST) private read-only request in order for us to get host information from request data.

For example let say the domain is example.com, and we have a tenant called company1, then the domain will be company1.example.com. Same thing for company2 tenant, the domain will be company2.example.com and so on.

config/MongooseConfigService.ts

import { Inject, Injectable, Scope } from "@nestjs/common";
import { REQUEST } from "@nestjs/core";
import { MongooseModuleOptions, MongooseOptionsFactory } from "@nestjs/mongoose";

@Injectable({scope:Scope.REQUEST})
export class MongooseConfigService implements MongooseOptionsFactory {
    constructor(@Inject(REQUEST) private readonly request,){}

  createMongooseOptions(): MongooseModuleOptions {
    let domain:string[]
    let database="database_development"
    if(this.request.data ){
      domain=this.request.data['host'].split('.')
      console.log(this.request)
    }
    else{
      domain=this.request['headers']['host'].split('.')
    }

    console.log(domain)
    if(domain[0]!='127' && domain[0]!='www' && domain.length >2){
      database="tenant_"+domain[0]
      console.log('current DB',database)
    }
    return {
      uri: 'mongodb://localhost:27017/'+database,
    };
  }
}

config/SequelizeConfigService.ts

import { Inject, Injectable, Scope } from "@nestjs/common";
import { REQUEST } from "@nestjs/core";
import { CONTEXT, RedisContext, RequestContext } from "@nestjs/microservices";
import { SequelizeModuleOptions, SequelizeOptionsFactory} from "@nestjs/sequelize";

@Injectable({scope:Scope.REQUEST})
export class SequelizeConfigService implements SequelizeOptionsFactory {
    constructor(@Inject(REQUEST) private readonly request:RequestContext){}
    
    createSequelizeOptions(): SequelizeModuleOptions {

      let domain:string[]
      let database="database_development"
      if(this.request.data ){
        domain=this.request.data['host'].split('.')
        console.log(this.request)
      }
      else{
        domain=this.request['headers']['host'].split('.')
      }

      console.log(domain)
      if(domain[0]!='127' && domain[0]!='www' && domain.length >2){
        database="tenant_"+domain[0]
        console.log('current DB',database)
      }

    return {
      dialect: 'mysql',
      host: 'localhost',
      port: 3306,
      username: 'ismaeil',
      password: 'root',
      database: database,
      autoLoadModels: true,
      synchronize: true,
    };
  }
}

Testing

After finishing the configuration, we need to do some work to test it because we need to map our localhost and IP to a domain. I will try to use two ways to test the application locally but for the production, it will be a configuration in your domain provider.

1- Edit the hosts file in your local machine and edit this file every time you add a tenant

Go to the following file in Linux: /etc/hosts and in windows: c:windowssystem32driversetchosts and add

## lines
127.0.0.1    example.com
127.0.0.1    company1.example.com
127.0.0.1    company2.example.com

2- Use local DNS

In Linux, you can install Dnsmasq and follow these steps:

1- Install dnsmasq in NetworkManager.

2- Add the configuration file sudo nano /etc/NetworkManager/dnsmasq.d/dnsmasq-localhost.conf.

add this line in the file:

address=/.example.com/127.0.0.1

3- Restart the service sudo systemctl reload NetworkManager.

The source code is available in the Git branch multi-database.

That’s all! In part 4, we are going to add a security level and user roles.