Jest test suite leaking memory

[mikro-orm]

Jest test suite leaking memory

[B4nan]

Yes, it is leaking, because for each test you are bootstrapping the application, but you never tear it down. Add this to the test file and the leak is gone:

  afterEach(async () => {
    await app.close();
  });

[Langstra]

Oh yea, forgot to add that in the reproduction repository. However, even after adding it the memory leak remains.

[Langstra]

I see that is responds to the onApplicationShutdown hook, but maybe it should be used in beforeApplicationShutdown? Since onApplicationShutdown will run after app.close resolves?

Also maybe enableShutdownHooks need to be enabled as they are by default disabled?

[B4nan]

Oh I see, it was more of a random "pass". Anyway, the "detect leaks" feature is experimental, for me it never worked correctly. See here for example:

jestjs/jest#5234

I see that is responds to the onApplicationShutdown hook, but maybe it should be used in beforeApplicationShutdown? Since onApplicationShutdown will run after app.close resolves?

Also maybe enableShutdownHooks need to be enabled as they are by default disabled?

This is based on the @nestjs/typeorm module, so I'd say that should be correct when it's done by the author of nest.

https://github.com/nestjs/typeorm/blob/master/lib/typeorm-core.module.ts#L102

Removing the onApplicationShutdown bit and explicitly calling orm.close() does not help. But I really believe this is more of a jest failure than actual leak. When I tried to duplicate the test 8 times and allowed garbage collection and heap logging, I can see the memory usage is consistent:

➜  nest-mikro-orm-jest-leak git:(master) ✗ node --expose-gc ./node_modules/.bin/jest --runInBand --logHeapUsage --config ./test/jest-e2e.json
 PASS  test/app1.e2e-spec.ts (62 MB heap size)
 PASS  test/app4.e2e-spec.ts (75 MB heap size)
 PASS  test/app5.e2e-spec.ts (76 MB heap size)
 PASS  test/app3.e2e-spec.ts (76 MB heap size)
 PASS  test/app7.e2e-spec.ts (76 MB heap size)
 PASS  test/app6.e2e-spec.ts (76 MB heap size)
 PASS  test/app2.e2e-spec.ts (76 MB heap size)
 PASS  test/app.e2e-spec.ts (76 MB heap size)