scala - Play tests with database: "Too many connections"

Question

To have a database available in scalatest with evolutions I use this extension of the default PlaySpec inspired by this SO question:

trait ResetDbSpec extends PlaySpec with BeforeAndAfterAll {
  lazy val appBuilder = new GuiceApplicationBuilder()
  lazy val injector = appBuilder.injector()
  lazy val databaseApi = injector.instanceOf[DBApi]

  override def beforeAll() = {
    Evolutions.applyEvolutions(databaseApi.database("default"))
  }

  override def afterAll() = {
    Evolutions.cleanupEvolutions(databaseApi.database("default"))
    databaseApi.database("default").shutdown()
  }
}

It applies database evolutions when the suite starts, and reverts them when the suite ends. A test then looks like

class ProjectsSpec extends ResetDbSpec with OneAppPerSuite { ...

After adding more tests like this, I hit a point where some tests that succeed when I run them alone, fail with this error:

com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Data source rejected establishment of connection, message from server: "Too many connections"

As can be see in the code above, I tried to add the line

databaseApi.database("default").shutdown()

in afterAll() to mitigate that, but it had no effect. I tried to not run tests in parallel, but no effect either. Where is it that I open db connections without closing them, and where should I call shutdown()?

N.B. I use Play 2.5.10 and Slick 3.1.

Answer 1

I have a lot of tests (about 500) and I don't get this error, the only difference I have with your code is that I add

databaseApi.database("default").getConnection().close()

and

Play.stop(fakeApplication)

for the integration tests.

Let me know if it changes anything.