Multiple database connections

[mikro-orm]

Multiple database connections

[EduVencovsky]

I'm still lost on how to connect to multiple databases (In my case, I want to connect to two different postgres databases).

Is there any way to do this without any problems or it still needs a PR?

[tsangste]

I tried my hand at implementing multiple database connections as this is something that would benefit us

[B4nan]

This will be caused by how the nest adapter registers the EM and repositories - both of your ORM instances will use the same tokens in the DI. You should be able to register things yourself manually.

Also you will need to handle the request context manually and give your ORM instances distinct names. See the tests:

https://github.com/mikro-orm/mikro-orm/blob/master/tests/RequestContext.test.ts#L64

We can definitly support this out of box, there will have to be some @InjectEntityManager(name) decorator, and the repository decorator will also need to have a name parameter. The adapter will then register all instances prefixed with the ORM instance name.

[B4nan]

Or actually this is already implemented, almost forgot about that - you can use MIKRO_ORM_CLI env var which will add the CLI config path.

You can also use different names for this file, simply rename it in the configPaths array your in package.json. You can also use MIKRO_ORM_CLI environment variable with the path to override configPaths value.

https://mikro-orm.io/docs/installation/#setting-up-the-commandline-tool

[AaronPerezPerez]

Hi again, what we finally did was to provide two different MikroORM instances instead of using the MikroOrmModule.forRoot() and then inject them in our repositories.
It looks like this:

@Global()
@Module({})
export class MikroOrmSwitcherModule {
  static init({ disable }: { disable: boolean }): DynamicModule {
    if (disable) {
      return {
        module: MikroOrmSwitcherModule,
      };
    }

    return {
      module: MikroOrmSwitcherModule,
      providers: [
        {
          provide: MIKRO_ORM_MONGODB_TOKEN,
          useValue: MikroORM.init(mikroOrmMongoConfig),
        },
        {
          provide: MIKRO_ORM_POSTGRESQL_TOKEN,
          useValue: MikroORM.init(mikroOrmPostgresConfig),
        },
      ],
      exports: [MIKRO_ORM_MONGODB_TOKEN, MIKRO_ORM_POSTGRESQL_TOKEN],
    };
  }
}

And this is the repository contructor:

  constructor(
    @Inject(MIKRO_ORM_POSTGRESQL_TOKEN) private readonly orm: MikroORM<PostgreSqlDriver>,
  ) {
    this.ledgerRepository = this.orm.em.getRepository(LedgerEntity);
  }

So we didn't need to finally use RequestContext at all.
We thought that this may be useful for you, so we wanted to share it!

[B4nan]

For reference, v6 also adds a --config CLI option:

mikro-orm/mikro-orm#3924

[B4nan]

You still need to register the request context yourself, as it was done automatically for you via MikroOrmModule.forRoot() that is no longer used.

Each request needs to have its own context, using global one will cause side effects and memory leaks.

https://mikro-orm.io/docs/identity-map/#why-is-request-context-needed

[jasonwilson]

@B4nan thanks for referencing this issue was able to setup a similar environment splitting out each database as a separate orm instance.

We rely in the mikro-orm cli which looks for mikro-orm.config.ts. Is there a a way to dynamically specify the configuration or connection in the cli? If not might be something to consider for v5.

[B4nan]

You could override most of the config option via env vars.

https://mikro-orm.io/docs/configuration/#using-environment-variables

[jasonwilson]

This would work as a "one off" for running commands but there's no way to inject or share .env configuration into the app when using multiple connections.

Another option would be to specify the mikro-orm.config.ts path via environment variable. I didn't see that option in the list, let me know if I missed it.

[B4nan]

Nope, that's not possible.

You can either wait for #545 or of course you could send a PR right ahead :]

If nobody contributes, will probably do it before v5 is out myself.

[jasonwilson]

I'm happy to open a PR for specifying orm config via env variable if you'll accept it.

[B4nan]

Sure we can start with that, I'd also add a CLI option for this ideally.

Just keep in mind that master is already v5 and I am not planning to backport features to v4, so if you will want to benefit from that, you will need to switch to v5 dev version.

[gianlazz]

I also have this as a required use case in the process of migrating from typeorm on an existing project where I had two databases supported. Using MIKRO_ORM_CLI appears to be working for me 🎉

For example, I have a mikro-orm.sqlite.config.js & mikro-orm.postgres.config.js file respectively for each. Then use commands as such:

$ MIKRO_ORM_CLI=$PWD/mikro-orm.sqlite.config.js mikro-orm debug
# or
$ MIKRO_ORM_CLI=$PWD/mikro-orm.postgres.config.js mikro-orm debug