How to make a Lagom streaming ServiceCall fail?

Lagom
, ,
1

I’m having a bit of troubles understanding the default behavior of a streaming ServiceCall:

// Definition
ServiceCall<Source<String, NotUsed>, Done> doSomething();

// Implementation
public ServiceCall<Source<String, NotUsed>, Done> doSomething() {
    return source -> {
        throw new TransportException(TransportErrorCode.InternalServerError, new ExceptionMessage("Internal server error", "..."));
    };
}

The consumer of this server however, never sees the TransportException

@Test
public void testShouldFail() {
    MyService service = server.client(MyService.class);

    Source<String, NotUsed> input = Source.empty();
    CompletableFuture<Done> future = service.doSomething().invoke(input).toCompletableFuture();

    ServiceTest.eventually(FiniteDuration.apply(5, SECONDS), () -> {
        assertThat(future.isCompletedExceptionally()).isTrue();
    });
}

I have the feeling that it has to do with some magic running under the hood, because when I move the TransportException outside of the lambda, the future fails as expected.

Is there anything I’m missing here?

2

Ok the issue has been found!

The key was to include .concat(Source.maybe()) to the test Source (in this case Source.empty().concat(Source.maybe())).

The second way was to increase the 5 seconds timeout, as it just needed more time and was therefor always failing…