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    <p>@Viktor Klang: We understand that <code>j.u.c.Future</code> is an abomination. But that's what we're getting back from a piece of software we must accept as given for the time being.</p> <p>So far, this is what we've hacked together:</p> <pre><code>def wrapJavaFutureInAkkaFuture[T](javaFuture: java.util.concurrent.Future[T], maybeTimeout: Option[Duration] = None)(implicit system: ActorSystem): akka.dispatch.Future[T] = { val promise = new akka.dispatch.DefaultPromise[T] pollJavaFutureUntilDoneOrCancelled(javaFuture, promise, maybeTimeout.map(_.fromNow)) promise } </code></pre> <p>In other words, create a separate Akka <code>Promise</code> (the write-side of a <code>Future</code>) corresponding to the <code>j.u.c.Future</code>, kicks off the callback <code>pollJavaFutureUntilDoneOrCancelled</code> to update the Promise by polling the "abomination", and returns the Promise to the caller.</p> <p>So how do we "poll" to update the Akka Promise based on the state of the j.u.c.Future?</p> <pre><code>def pollJavaFutureUntilDoneOrCancelled[T](javaFuture: java.util.concurrent.Future[T], promise: akka.dispatch.Promise[T], maybeDeadline: Option[Deadline] = None)(implicit system: ActorSystem) { if (maybeDeadline.exists(_.isOverdue)) javaFuture.cancel(true); if (javaFuture.isDone || javaFuture.isCancelled) { promise.complete(allCatch either { javaFuture.get }) } else { Play.maybeApplication.foreach { implicit app =&gt; system.scheduler.scheduleOnce(50 milliseconds) { pollJavaFutureUntilDoneOrCancelled(javaFuture, promise, maybeDeadline) } } } } </code></pre> <p>This is an attempt at what was hinted at in the google groups discussion that I referenced in the question. It uses the Akka scheduler to call itself back every 50 ms to check if the j.u.c.Future is either done or cancelled. Whenever that happens, it updates the Akka Promise with the completed state.</p> <p>@Victor Klang, et al: </p> <p>Is this best practice? Do you know of a better way to do this? Are we missing a downside here that we should know about?</p> <p>Thanks for any more help.</p>
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    1. POHow do I wrap a java.util.concurrent.Future in an Akka Future?
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    1. POHow do I wrap a java.util.concurrent.Future in an Akka Future?
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    1. COOne obvious downside is, that in the worst case this will cause a high delay of the response. If you have for example the default settings and your future completes 1 ms after the check, it can cause a delay of about 100ms. This can however be adjusted by setting the `scheduler.tick-duration` setting in the config.
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    2. CO@drexin true, but a tick duration and poll frequency trade-off will be present in any polling based solution, right?
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    3. COSure, but as you asked for downsides I just wanted to tell you, that it does not only depend on the delay param of the `scheduleOnce` call, but also on the setting in the akka config. If you can live with a delay this should be a usable solution.
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