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,而且我不想阻塞当前线程。我使用 Akka Futures 来包装数据库调用。
我不想等待(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 Controller 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))
}
最佳答案
你很接近。您可以简单地调用 map
promise 来处理它。在 Async block 内,它保持非阻塞。 Relevant documentation (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:
从您下面的评论中,让我们仔细看看 Async block 。 Async
接受一个 Promise
,并返回一个 AsyncResult
,它是 Result
的子类型( >行动
需要)。
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,因此它保持非阻塞。整个 block 快速返回一个 AsyncResult
,开始玩吧!以类似的方式管理它,在它完成时返回给客户端(同时释放 Play! 去做其他事情)。
关于scala - 玩转 2.0 Scala 和异步回调,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/12585232/