Scala future 及其回调在相同的执行上下文中工作

Question

我通过 Akka actor 调用 def activateReward 并且执行 OracleClient.rewardActivate(user) 有时非常慢（数据库不在我的职责范围内，属于另一家公司）。

当数据库速度慢时，线程池耗尽并且无法有效地分配更多线程给运行回调 future.onComplete 因为回调和 futures 在相同的执行上下文中工作。

请告知如何从为期货分配的线程异步执行回调中的代码OracleClient.rewardActivate（用户）

class RewardActivatorHelper {

  private implicit val ec = new ExecutionContext {
    val threadPool = Executors.newFixedThreadPool(1000)
    def execute(runnable: Runnable) {threadPool.submit(runnable)}
    def reportFailure(t: Throwable) {throw t}
  }

  case class FutureResult(spStart:Long, spFinish:Long)

  def activateReward(msg:Msg, time:Long):Unit = {
    msg.users.foreach {
      user =>
        val future:Future[FutureResult] = Future {
          val (spStart, spFinish) = OracleClient.rewardActivate(user)
          FutureResult(spStart, spFinish)
        }

        future.onComplete {
          case Success(futureResult:FutureResult) =>
            futureResult match {
              case res:FutureResult => Logger.writeToLog(Logger.LogLevel.DEBUG,s"started:${res.spStart}finished:${res.spFinish}")
              case _ => Logger.writeToLog(Logger.LogLevel.DEBUG, "some error")
            }

          case Failure(e:Throwable) => Logger.writeToLog(Logger.LogLevel.DEBUG, e.getMessage)    
        }
    }
  }
}

Answer 1

您可以通过以下方式为 onComplete 回调显式指定执行上下文，而不是隐式指定执行上下文：

import java.util.concurrent.Executors
import scala.concurrent.duration.Duration

object Example extends App {
  import scala.concurrent._

  private implicit val ec = new ExecutionContext {
    val threadPool = Executors.newFixedThreadPool(1000)
    def execute(runnable: Runnable) {threadPool.submit(runnable)}
    def reportFailure(t: Throwable) {throw t}
  }

  val f = Future {
    println("from future")
  }

  f.onComplete { _ =>
    println("I'm done.")
  }(scala.concurrent.ExecutionContext.Implicits.global)

  Await.result(f, Duration.Inf)
}

这当然不会解决数据库跟不上的根本问题，但无论如何了解它可能是件好事。

澄清一下：我让 onComplete 回调由标准 global 执行上下文处理。您可能想创建一个单独的。

Scala future 及其回调在相同的执行上下文中工作

Scala future and its callback works in the same execution context

multithreading

scala

concurrency

callback

future