Akka-http exception handling (Scala) - scala

Question

I am using Akka-hhtp (scala) to send multiple http batch requests asynchronously to an API and wondering what is the right way to handle exceptions when the response code is other than 200 OK.
Below is some pseudo-code to demonstrate my point.
/* Using For comprehension here because the server API has restriction on the amount of data we can send and the time it takes them to process each request. So they require us to send multiple mini requests instead. If one of those fails, then our entire job should fail.*/
val eventuallyResponses = for {
batches <- postBatch(payload)
} yield batches
val eventualResponses = Future.sequence(eventuallyResponses)
/* Do I need to recover here? If I don't, will the actor system terminate? */
eventualResponses.recover { case es =>
log.warn("some message")
List()
}
/* As I said I need to wait for all mini batch requests to complete. If one response is different than 200, then the entire job should fail. */
val result = Await.result(eventualResponses, 10.minutes)
actorSystem.terminate().oncomplete{
case Success(_) =>
if (result.isEmpty) =>
/* This doesn't seem to interrupt the program */
throw new RuntimeException("POST failed")
} else {
log.info("POST Successful")
}
case Failure(ex) =>
log.error("error message $ex")
throw ex
}
def postBatch(payload) = {
val responseFuture: Future[HttpResponse] = httpClient.post(payload)
responseFuture.flatMap{ res =>
res.status match {
case StatusCodes.OK => Future.successful(res)
case _ => Future.failed(new RuntimeException("error message"))
}
}
}
The above code throws exception when we receive StatusCodes different than OK. It does go through the branch of result.isEmpty true, but it doesn't seem to stop/interrupt the execution of the program. I need it to do that, as this is scheduled as an Autosys job, and I need to make the job fail if at least one of the batch requests returns different response than 200 OK.
If I don't recover and let the exception be thrown then (when we receive non 200 status code), will the Actor System be terminated properly?
Do you know of a good way to do the above?
Thanks :)

Answer 1

As far as I understand your question you need to throw an exception from main body if some responses haven't status 200.
def postBatch(payload: HttpRequest)(implicit system: ActorSystem, ec: ExecutionContext): Future[HttpResponse] = {
Http().singleRequest(payload).flatMap(response => response.status match {
case StatusCodes.OK => Future.successful(response)
case _ => Future.failed(new RuntimeException("error message"))
})
}
val reuests: List[HttpRequest] = List(...)
/*
You don't need for comprehension here because
val eventuallyResponses = for {
batches <- postBatch(payload)
} yield batches
is equal to
val eventuallyResponses = postBatch(payload)
For comprehension doesn't process recursive sending. If you need it you should write it yourself by flatMap on each request future.
*/
val eventualResponses: Future[List[HttpResponse]] =
Future.sequence(reuests.map(postBatch)) //also, its better to add some throttling logic here
//as far as i understand you need to wait for all responses and stop the actor system after that
Await.ready(eventualResponses, 10 minutes) //wait for all responses
Await.ready(actorSystem.terminate(), Duration.Inf) //wait for actor system termination
//because of Await.ready(eventualResponses, 10 minutes) we can match on the future value and expect that it should be completed
eventualResponses.value match {
case Some(Success(responses)) =>
log.info("All requests completed")
case Some(Failure(exception)) =>
log.error("Some request failed")
throw exception //rethrow this exception
case None =>
log.error("Requests timed out")
throw RuntimeException("Requests timed out")
}