使用期货时程序不会终止

Question

我正在尝试对目录中的每个文件同时运行一个函数。可悲的是，每当我使用 Futures 时，我的程序都不想终止（运行s 永远）。我尝试使用 Await.result() 得到相同的结果：/

当运行ning 代码执行正常时，甚至“完成”？打印出来然后挂起...

这是我的代码。（我是 Scala 新手）

val execService = Executors.newFixedThreadPool(3)
implicit val execContext = ExecutionContext.fromExecutorService(execService)

val futures = for (file <- filesList) yield Future {
   println(file)
   // theFunc(file)
}
val seq = Future.sequence(futures)
seq.onComplete {
   case Success(x) => println("finish?")
   case Failure(e) => println(e)
}

Answer 1

Executors.newFixedThreadPool 在后台使用 defaultThreadFactory 创建非守护线程

Returns a default thread factory used to create new threads. This factory creates all new threads used by an Executor in the same ThreadGroup... Each new thread is created as a non-daemon thread

因为这些是非守护线程，所以程序不会终止。另一方面，例如，scala.concurrent.ExecutionContext.Implicits.global 创建 daemon 个线程

val threadFactory = new DefaultThreadFactory(daemonic = true,
                                             maxBlockers = getInt("scala.concurrent.context.maxExtraThreads", "256"),
                                             prefix = "scala-execution-context-global",
                                             uncaught = (thread: Thread, cause: Throwable) => reporter(cause))

我们注意到 daemonic = true，所以下面的程序将在最后终止

implicit val execContext = scala.concurrent.ExecutionContext.Implicits.global

val futures = for (file <- filesList) yield Future {
   println(file)
   // theFunc(file)
}
...

基于

使用期货时程序不会终止

Program not terminating when using Futures

concurrency

scala

future

file