nestjs-typeorm-transactions-test

Description

A NestJS module to make TypeORM transaction management easier across different services.

How it works

This package can be used to reduce the boilerplate code needed to manage TypeORM transactions. It acts as a wrapper around the actual TypeORM package that enables effortless transaction support. The package utilizes async local storage in order to share transactional entity manager accross different service method calls so that transactions across multiple services are handled behind the scenes and abstracted away from developers.

Note: In the following code snippets, only the imports relvant to this package are shown

How to use it

Importing TypeOrmTransactionModule

You should ideally import TypeOrmTransactionModule.forRoot() in your app.module.ts file and the configuration options are exactly the same as @nestjs/typeorm package.

Add the following to the imports array of your module:

import { TypeOrmTransactionModule } from 'nestjs-typeorm-transactions';

@Module({
  imports: [
    TypeOrmTransactionModule.forRoot({
      type: 'mysql', // or postgres, sqlite etc
      host: 'localhost',
      username: 'username',
      password: 'password',
      database: 'test',
      entities: [User], // list of entities
      synchronize: true,
      logging: true,
    }),
  ],
})
export class AppModule {}

For a repository to be avilable in the context of a sub module, we need to import TypeOrmTransactionModule.forFeature() in that module's import array. Just like @nestjs/typeorm package, we can pass an array of entities whose repositories will be available in this module.

import { TypeOrmTransactionModule } from 'nestjs-typeorm-transactions';

@Module({
  imports: [TypeOrmTransactionModule.forFeature([User])],
  controllers: [UsersController],
  providers: [UsersService],
})
export class UsersModule {}

Injecting repositories and runnning queries in transactions

The way repositories are injected are almost the same as @nestjs/typeorm package. Only difference is that you need to use @InjectTransactionalRepository. The entity for which repository will be injected should be povided to this decorator as well.

import {
  InjectTransactionalRepository,
  TransactionalRepository,
} from 'nestjs-typeorm-transactions';

class UsersService {
  constructor(
    @InjectTransactionalRepository(User)
    private userRepository: TransactionalRepository<User>,
  ) {}

  async doSomethingWithUser() {
    // ...
  }
}

As seen above, the type of injected repository is TransactionalRepository. By default, the queries are NOT wrapped inside a transaction even if you inject TransactionalRepository into your service class. In order to run queries in a transaction, @Transactional decorator must be used on the route handler that is calling the service method. Here's an example:

import { Transactional } from 'nestjs-typeorm-transactions';

@Controller('users')
export class UsersController {
  constructor(private usersService: UsersService) {}

  @Post('with-transaction')
  @Transactional()
  async withTransaction() {
    await this.usersService.doSomethingWithUser();
  }

  @Post('without-transaction')
  async withTransaction() {
    await this.usersService.doSomethingWithUser();
  }
}

If a request hits the endpoint /users/with-transcation, any database query executed by doSomethingWithUser or any other service method that doSomethingWithUser method calls, all of these queries will be wrapped in a transaction as we have used @Transactional decorator.

However, if a request hits the other endpoint /users/without-transcation, no transaction will be created. So it's crucial to remember to add @Transactional decorator on route handlers where we need atomicity.

Connecting to multiple databases

Connecting to multiple databases is supported by @nestjs/typeorm package and it's also supported by this package. In order to accomplish this, TypeOrmTransactionModule.forRoot() should be imported multiple times as follows:

import { TypeOrmTransactionModule } from 'nestjs-typeorm-transactions';

@Module({
  imports: [
    TypeOrmTransactionModule.forRoot({
      type: 'mysql',
      host: 'mysql_host',
      username: 'mysql_username',
      password: 'mysql_password',
      database: 'test_mysql',
      entities: [User],
      synchronize: true,
      logging: true,
    }),
    TypeOrmTransactionModule.forRoot({
      name: 'second_db', // name for the postgresql db connection
      type: 'postgres',
      host: 'postgres_host',
      username: 'postgres_username',
      password: 'postgres_password',
      database: 'test_postgres',
      entities: [Article],
      synchronize: true,
      logging: true,
    }),
  ],
})
export class AppModule {}

In this case, we have two database connections. The first one is the default one and it's the mysql database. The second connection is for a postgresql database and it's used to store the articles. The name specified for the postgresql database is second_db and it will be used later on.

In order to make repositories for both of these connections available in the users module's context, we import them both as follows:

import { TypeOrmTransactionModule } from 'nestjs-typeorm-transactions';

@Module({
  imports: [
    TypeOrmTransactionModule.forFeature([User]), // will use the default connection (mysql)
    TypeOrmTransactionModule.forFeature([Article], 'second_db'), // will use postgresql connection
  ],
  controllers: [UsersController],
  providers: [UsersService],
})
export class UsersModule {}

How we inject repositories remains exactly the same:

import {
  InjectTransactionalRepository,
  TransactionalRepository,
} from 'nestjs-typeorm-transactions';

class UsersService {
  constructor(
    @InjectTransactionalRepository(User)
    private userRepository: TransactionalRepository<User>,
    @InjectTransactionalRepository(Article)
    private userRepository: TransactionalRepository<Article>,
  ) {}

  async doSomethingWithUser() {
    // ...
  }

  async doSomethingWithArticle() {
    // ...
  }
}

And lastly, for transactional query execution, we need to use @Transactional decorator as follows:

import { Transactional } from 'nestjs-typeorm-transactions';

@Controller('users')
export class UsersController {
  constructor(private usersService: UsersService) {}

  @Post()
  @Transactional()
  async withTransaction() {
    await this.usersService.doSomethingWithUser();
  }

  @Post('/articles')
  @Transactional('second_db')
  async withTransaction() {
    await this.usersService.doSomethingWithArticle();
  }
}

When @Transactional decorator is added without any argument, it will wrap all database queries executed by the default connection in a transaction (mysql connection in this case). However, the second decorator has the argument second_db which means in the route /users/articles, only the database queries that are sent to the postgres database will be in a transaction.