播放2.0 Scala和异步回调

Question

我想对我的数据库进行两次调用,这将需要一段时间才能返回结果,我不想阻止当前线程.我用Akka Futures来包装数据库调用.

我没有等待(阻塞)两个调用返回,而是指定要调用的回调函数,然后可以呈现响应.我怎么做？这是我的控制器代码:

def showPie = IsAuthenticated(Roles.validator) { user => implicit request =>
    val eventUid = request.session.get(EventUid).get

    val printed = Akka.future(TicketRepository.getCountForState(eventUid, "Printed"))
    val validated = Akka.future(TicketRepository.getCountForState(eventUid, "Validated"))

    //this would be evil, because it would block: Ok(views.html.pie(printed.await(1000).get, validated.await(1000).get)) 

    //create a promise for all the promised results
    val promise = Promise.sequence(List(printed, validated))

    //this doesnt work, but how can I make it work WITHOUT blocking this thread?
    promise.callWhenResultIsReady(Ok(view.html.pie(promise.get))
}

Answer 1

你很亲密 您可以简单地致电map承诺来处理它.在异步块内部,它保持非阻塞状态.相关文档(参见"AsyncResult").

def showPie = IsAuthenticated(Roles.validator) { user => implicit request =>
    val eventUid = request.session.get(EventUid).get

    val printed = Akka.future(TicketRepository.getCountForState(eventUid, "Printed"))
    val validated = Akka.future(TicketRepository.getCountForState(eventUid, "Validated"))

    //create a promise for all the promised results
    val promise = Promise.sequence(List(printed, validated))
    Async {
        promise map { res =>
            Ok("Got it!" + res)
        }
    }
}

编辑: 从下面的评论中,让我们仔细看看异步块.Async取aPromise,并返回aAsyncResult,这是Result(Action需要的)子类型.

    Async {
        // We take the promise, and add something akin to a callback
        //  function with `map`. This new function is called when `promise`
        //  is complete.
        val result = promise map { res => // this is the redeemed promise
          Ok("Got it!" + res)
        }
        result // this is the new promise
    } 

由于map函数在promise完成时被调用,因此保持非阻塞状态.整个块快速返回AsyncResult,并播放!通过在完成时返回客户端(并释放Play!同时执行其他操作)以类似的方式管理它.