An unbounded queue in front of a Akka HTTP's superPool connection flow. In some cases this might be a solution to the overflowing connection pool (akka.stream.BufferOverflowException) from single requests. In some other cases this is very bad idea.

If you application makes a potentially unbounded stream of requests, then you should follow Akka's documentation and not use this.

Otherwise this is a drop in replacement of Http().singleRequest.

import httpqueue._
import akka.actor._
import akka.http.scaladsl.model._
val system = ActorSystem("test")
val request : HttpRequet = ???
val response : Future[HttpResponse] = HttpQueue(system).queue(request)

HttpQueue.queue is a HttpRequest => Future[HttpResponse]. The request is sent to an ActorPublisher which either queues it up, or forwards to the pipeline.

HttpQueue is an Akka Extension, thus is unique per ActorSystem and the Http().superPool() flow is materialized only once per ActorSystem.

There is a graph stage based variant as well.

MIT (c) Istvan Bartha, except callbackwrapper.scala which is copied from Akka's source and is Apache 2.