Multi-tenant Mongoose module for Nest

app.module.ts

import { Module } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { TenancyModule } from '@app/tenancy';
import { OrderModule } from './order';
import { PaymentModule } from './payment';
import { Request } from 'express';

@Module({
  imports: [TenancyModule.forRoot({
    tenantId: (req: Request) => req.get('X-TenantId'),
    options: () => ({}),
    uri: (tenantId: string) => `mongodb://localhost/tenant-${tenantId}`,
  }), OrderModule, PaymentModule],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {}

factories-index.ts

import { getTenantModelToken, getTenantModelDefinitionToken } from '../utils';
import {
  ModelDefinition,
  ModelDefinitionMap,
  ConnectionMap,
} from '../types';
import { Provider, Scope } from '@nestjs/common';
import { Token } from '../enums';
import * as mongoose from 'mongoose';

export const createProviders = (definitions: ModelDefinition[]): Provider[] => {
  const providers: Provider[] = [];

  definitions.forEach(definition => {
    const { name, schema, collection } = definition;

    providers.push({
      inject: [
        Token.MODEL_DEFINITION_MAP,
        Token.CONNECTION_MAP,
      ],
      provide: getTenantModelDefinitionToken(name),
      useFactory: (
        modelDefinitionMap: ModelDefinitionMap,
        connectionMap: ConnectionMap,
      ) => {
        const exists = modelDefinitionMap.has(name);
        if (!exists) {
          modelDefinitionMap.set(name, { ...definition });
          connectionMap.forEach(connection => {
            connection.model(name, schema, collection);
          });
        }
      },
    });

    providers.push({
      inject: [Token.TENANT_CONNECTION],
      provide: getTenantModelToken(name),
      scope: Scope.REQUEST,
      useFactory: (tenantConnection: mongoose.Connection) =>
        tenantConnection.model(name),
    });
  });

  return providers;
};

order.module.ts

import { Module } from '@nestjs/common';
import { OrderService } from './order.service';
import { OrderController } from './order.controller';
import { TenancyModule } from '@app/tenancy';
import { OrderSchema } from './schemas';

@Module({
  imports: [TenancyModule.forFeature([{ name: 'Order', schema: OrderSchema }])],
  providers: [OrderService],
  controllers: [OrderController],
})
export class OrderModule {}

order.service.ts

import { Injectable } from '@nestjs/common';
import { InjectTenantModel } from '@app/tenancy';
import { Model } from 'mongoose';
import { Order } from './interfaces';
import { CreateOrderDto } from './dtos';

@Injectable()
export class OrderService {
  constructor(
    @InjectTenantModel('Order') private readonly orderModel: Model<Order>,
  ) {}

  async create(dto: CreateOrderDto): Promise<Order> {
    return new this.orderModel(dto).save()
  }

  async findAll(): Promise<Order[]> {
    return this.orderModel.find().exec()
  }
}

tenancy-feature.module.ts

import { createProviders } from './factories';
import { Global, Module, DynamicModule } from '@nestjs/common';
import {
  ModelDefinition,
} from './types';

@Global()
@Module({})
export class TenancyFeatureModule {
  static register(models: ModelDefinition[]): DynamicModule {
    const providers = createProviders(models);
    return {
      module: TenancyFeatureModule,
      providers,
      exports: providers,
    };
  }
}

tenancy-root.module.ts

import {
  Global,
  Module,
  DynamicModule,
  Scope,
  OnApplicationShutdown,
} from '@nestjs/common';
import { REQUEST, ModuleRef } from '@nestjs/core';
import { Request } from 'express';
import {
  TenancyModuleOptions,
  ConnectionMap,
  ModelDefinitionMap,
} from './types';
import { Token } from './enums';
import * as mongoose from 'mongoose';

@Global()
@Module({})
export class TenancyRootModule implements OnApplicationShutdown {
  constructor(private readonly moduleRef: ModuleRef) {}

  async onApplicationShutdown() {
    const connectionMap: ConnectionMap = this.moduleRef.get(
      Token.CONNECTION_MAP,
    );
    await Promise.all(
      [...connectionMap.values()].map(connection => connection.close()),
    );
  }

  static register(options: TenancyModuleOptions): DynamicModule {
    const tenancyModuleOptions = {
      provide: Token.TENANCY_MODULE_OPTIONS,
      useValue: { ...options },
    };

    const connectionMap = {
      provide: Token.CONNECTION_MAP,
      useFactory: (): ConnectionMap => new Map(),
    };

    const modelDefinitionMap = {
      provide: Token.MODEL_DEFINITION_MAP,
      useFactory: (): ModelDefinitionMap => new Map(),
    };

    const tenantConnection = {
      inject: [
        REQUEST,
        Token.TENANCY_MODULE_OPTIONS,
        Token.CONNECTION_MAP,
        Token.MODEL_DEFINITION_MAP,
      ],
      provide: Token.TENANT_CONNECTION,
      scope: Scope.REQUEST,
      useFactory: async (
        req: Request,
        options: TenancyModuleOptions,
        connectionMap: ConnectionMap,
        modelDefinitionMap: ModelDefinitionMap,
      ): Promise<mongoose.Connection> => {
        const tenantId = options.tenantId(req);
        const exists = connectionMap.has(tenantId);
        if (exists) {
          return connectionMap.get(tenantId);
        }
        const connection = mongoose.createConnection(options.uri(tenantId), {
          useNewUrlParser: true,
          useUnifiedTopology: true,
          ...options.options(tenantId),
        });
        modelDefinitionMap.forEach(definition => {
          const { name, schema, collection } = definition;
          connection.model(name, schema, collection);
        });
        connectionMap.set(tenantId, connection);
        return connection;
      },
    };

    const providers = [
      modelDefinitionMap,
      tenancyModuleOptions,
      tenantConnection,
      connectionMap,
    ];

    return {
      module: TenancyRootModule,
      providers,
      exports: providers,
    };
  }
}

tenancy.module.ts

import {
  ModelDefinition,
  TenancyModuleOptions,
} from './types';
import { Module, DynamicModule } from '@nestjs/common';
import { TenancyRootModule } from './tenancy-root.module';
import { TenancyFeatureModule } from './tenancy-feature.module';

@Module({})
export class TenancyModule {
  static forRoot(options: TenancyModuleOptions): DynamicModule {
    return {
      module: TenancyModule,
      imports: [TenancyRootModule.register(options)],
    };
  }

  static forFeature(models: ModelDefinition[]): DynamicModule {
    return {
      module: TenancyModule,
      imports: [TenancyFeatureModule.register(models)],
    };
  }
}

@Robokishan I can't retrieve the code. As far as I remember, it was a convenience method using @Inject().