将来在回调中运行在同一个线程中
将来在回调中运行在同一个线程中
提问于 2013-11-24 12:11:38
当我运行这段代码时：
val intList = List(1, 6, 8)
val listOfFutures = intList.map{
i => future {
println("future " +i)
Thread.sleep(i* 1000)
if (i == 12)
throw new Exception("6 is not legal.")
i
}
}
val futureOfList = Future.sequence(listOfFutures)
futureOfList onSuccess{
case int => {
logInfo("onSuccess")
int.foreach(i => {
Future{
logInfo("h : " + i)
}
})
}
}
futureOfList onFailure{
case int => {
logInfo("onFailure")
}
}
logInfo("after")嵌套期货运行的线程都是相同的：
future 1
2013/11/24 11:55:00.002 [ModelUtilsTest] [main]: INFO: [] after
future 6
future 8
2013/11/24 11:55:14.878 [ModelUtilsTest] [ForkJoinPool-1-worker-1]: INFO: [] onSuccess
2013/11/24 11:55:15.378 [ModelUtilsTest] [ForkJoinPool-1-worker-1]: INFO: [] h : 1
2013/11/24 11:55:15.378 [ModelUtilsTest] [ForkJoinPool-1-worker-1]: INFO: [] h : 6
2013/11/24 11:55:15.378 [ModelUtilsTest] [ForkJoinPool-1-worker-1]: INFO: [] h : 8为什么会发生这种事？我需要内在的未来并行运行。
回答 2
Stack Overflow用户
回答已采纳
发布于 2013-11-24 14:34:34
Future实现检查它是否要在拥有当前线程的ForkJoinPool上运行某些东西。在这种情况下，它将ForkJoinTask.fork()，它将新的工作单元添加到当前工作线程的工作队列中。任何其他线程都必须窃取该工作才能执行它。您不会期望在可用线程上看到任务的统一分布，特别是对于琐碎的任务。
在接下来的运行中，worker-9首当其冲：
scala> val f = Future sequence (1 to 20 map (i => Future(i)))
f: scala.concurrent.Future[scala.collection.immutable.IndexedSeq[Int]] = scala.concurrent.impl.Promise$DefaultPromise@47fe4ff8
scala> f onSuccess { case is => is foreach (i => Future(println(s"$i on ${Thread.currentThread}"))) }
scala> 2 on Thread[ForkJoinPool-1-worker-9,5,main]
5 on Thread[ForkJoinPool-1-worker-15,5,main]
4 on Thread[ForkJoinPool-1-worker-3,5,main]
6 on Thread[ForkJoinPool-1-worker-9,5,main]
1 on Thread[ForkJoinPool-1-worker-5,5,main]
12 on Thread[ForkJoinPool-1-worker-7,5,main]
11 on Thread[ForkJoinPool-1-worker-9,5,main]
15 on Thread[ForkJoinPool-1-worker-9,5,main]
16 on Thread[ForkJoinPool-1-worker-9,5,main]
17 on Thread[ForkJoinPool-1-worker-9,5,main]
18 on Thread[ForkJoinPool-1-worker-9,5,main]
19 on Thread[ForkJoinPool-1-worker-9,5,main]
20 on Thread[ForkJoinPool-1-worker-9,5,main]
3 on Thread[ForkJoinPool-1-worker-1,5,main]
10 on Thread[ForkJoinPool-1-worker-13,5,main]
9 on Thread[ForkJoinPool-1-worker-11,5,main]
8 on Thread[ForkJoinPool-1-worker-3,5,main]
7 on Thread[ForkJoinPool-1-worker-15,5,main]
14 on Thread[ForkJoinPool-1-worker-7,5,main]
13 on Thread[ForkJoinPool-1-worker-5,5,main]Stack Overflow用户
发布于 2013-11-24 12:25:21
有两种方法可以轻松地实现并行性：
首先，您可以从traverse伙伴对象中使用Future方法。
import scala.collection.breakOut
import scala.concurrent.Future;
import scala.concurrent.ExecutionContext.Implicits.global
val modifiedList = Future.traverse(myList)(myFunc)或者您可以使用par集合，它并行地运行映射。
val modifiedList = myList.par.map(myFunc)(breakOut)页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/20174300
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