Transactions with NestJS and TypeORM - decorators and unit tesing

Question

My Question is around transaction management using nestjs and Typeorm, my db is postgres.

Should I use decorators like @Transaction and @TransactionManager while doing transaction management. I heard that they are going to be removed in new releases. https://github.com/typeorm/typeorm/issues/3251
As a best practise how do we handle a transaction that is inserting or updating multiple tables. I see the following question nestjs / TypeOrm database transaction Is this the right away, can somebody give me a full example. Should I inject connection to my service class and get EntityManager from it and pass it around?
What would be the right way for unit testing such an insert on two tables.

I am right now using Transaction decorators from TypeOrm. All my create code is in a single class, I want to be able to move the code for creation of every entity to be moved to the entity's own service class and expect the transaction rollback still works.

@Transaction({ isolation: "SERIALIZABLE" })
    async createProfile(createProfileDTO: CreateProfileDTO, @TransactionManager() manager?: EntityManager){
...
const profileRepository = manager.getRepository(Profile);
let savedProfile = await profileRepository.save<Profile>(profile);

identifier.profile = savedProfile;
 const identifierRepository = manager.getRepository(Identifier);
 let savedIdentifier = identifierRepository.save(identifier);

}

Alternatively, if I use

 await this.connection.transaction(async transactionalEntityManager => {
            profile = await this.createUserProfile(createProfileDTO, transactionalEntityManager);
            identifiers = await this.identifierService.createIdentifier(profile, createProfileDTO
                , transactionalEntityManager);
});

What is the best way to unit test the above code?

Hitesh Joshi Hitesh Joshi · Accepted Answer · 2019-12-07T03:57:35

I ended up using a Connection object instead of decorators

@InjectConnection()
private readonly connection: Connection)

then make calls to all services like so

await this.connection.transaction(async transactionalEntityManager => {
                try {
                    urDTOCreated = await this.myService1.createSomething(urDTO, transactionalEntityManager);
                    typeDTOCreated = await this.myService2.createSomethingElse(obj1, obj2, transactionalEntityManager);
                }
                catch (ex) {
                    Logger.log(ex);
                    throw new InternalServerErrorException("Error saving data to database");
                }

With that, you can test your services independently and can test your controller as well for managed transaction

Transactions with NestJS and TypeORM - decorators and unit tesing

1 Answers