Akka/Scala example source code file (ThreadPoolBuilder.scala)

This example Akka source code file (ThreadPoolBuilder.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Akka and Scala source code examples by using tags.

All credit for the original source code belongs to akka.io; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Akka tags/keywords

akka, boolean, callable, concurrent, dispatch, duration, executorservice, forkjoin, int, queuefactory, runnable, t, threadfactory, threadpoolconfigbuilder, threadpoolexecutor, time

The ThreadPoolBuilder.scala Akka example source code

/**
 * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
 */

package akka.dispatch

import java.util.Collection
import scala.concurrent.{ Awaitable, BlockContext, CanAwait }
import scala.concurrent.duration.Duration
import scala.concurrent.forkjoin._
import java.util.concurrent.{
  ArrayBlockingQueue,
  BlockingQueue,
  Callable,
  ExecutorService,
  LinkedBlockingQueue,
  RejectedExecutionHandler,
  RejectedExecutionException,
  SynchronousQueue,
  TimeUnit,
  ThreadFactory,
  ThreadPoolExecutor
}
import java.util.concurrent.atomic.{ AtomicReference, AtomicLong }

object ThreadPoolConfig {
  type QueueFactory = () ⇒ BlockingQueue[Runnable]

  val defaultAllowCoreThreadTimeout: Boolean = false
  val defaultCorePoolSize: Int = 16
  val defaultMaxPoolSize: Int = 128
  val defaultTimeout: Duration = Duration(60000L, TimeUnit.MILLISECONDS)
  val defaultRejectionPolicy: RejectedExecutionHandler = new SaneRejectedExecutionHandler()

  def scaledPoolSize(floor: Int, multiplier: Double, ceiling: Int): Int =
    math.min(math.max((Runtime.getRuntime.availableProcessors * multiplier).ceil.toInt, floor), ceiling)

  def arrayBlockingQueue(capacity: Int, fair: Boolean): QueueFactory = () ⇒ new ArrayBlockingQueue[Runnable](capacity, fair)

  def synchronousQueue(fair: Boolean): QueueFactory = () ⇒ new SynchronousQueue[Runnable](fair)

  def linkedBlockingQueue(): QueueFactory = () ⇒ new LinkedBlockingQueue[Runnable]()

  def linkedBlockingQueue(capacity: Int): QueueFactory = () ⇒ new LinkedBlockingQueue[Runnable](capacity)

  def reusableQueue(queue: BlockingQueue[Runnable]): QueueFactory = () ⇒ queue

  def reusableQueue(queueFactory: QueueFactory): QueueFactory = reusableQueue(queueFactory())
}

/**
 * Function0 without the fun stuff (mostly for the sake of the Java API side of things)
 */
trait ExecutorServiceFactory {
  def createExecutorService: ExecutorService
}

/**
 * Generic way to specify an ExecutorService to a Dispatcher, create it with the given name if desired
 */
trait ExecutorServiceFactoryProvider {
  def createExecutorServiceFactory(id: String, threadFactory: ThreadFactory): ExecutorServiceFactory
}

/**
 * A small configuration DSL to create ThreadPoolExecutors that can be provided as an ExecutorServiceFactoryProvider to Dispatcher
 */
final case class ThreadPoolConfig(allowCorePoolTimeout: Boolean = ThreadPoolConfig.defaultAllowCoreThreadTimeout,
                                  corePoolSize: Int = ThreadPoolConfig.defaultCorePoolSize,
                                  maxPoolSize: Int = ThreadPoolConfig.defaultMaxPoolSize,
                                  threadTimeout: Duration = ThreadPoolConfig.defaultTimeout,
                                  queueFactory: ThreadPoolConfig.QueueFactory = ThreadPoolConfig.linkedBlockingQueue(),
                                  rejectionPolicy: RejectedExecutionHandler = ThreadPoolConfig.defaultRejectionPolicy)
  extends ExecutorServiceFactoryProvider {
  class ThreadPoolExecutorServiceFactory(val threadFactory: ThreadFactory) extends ExecutorServiceFactory {
    def createExecutorService: ExecutorService = {
      val service: ThreadPoolExecutor = new ThreadPoolExecutor(
        corePoolSize,
        maxPoolSize,
        threadTimeout.length,
        threadTimeout.unit,
        queueFactory(),
        threadFactory,
        rejectionPolicy) with LoadMetrics {
        def atFullThrottle(): Boolean = this.getActiveCount >= this.getPoolSize
      }
      service.allowCoreThreadTimeOut(allowCorePoolTimeout)
      service
    }
  }
  final def createExecutorServiceFactory(id: String, threadFactory: ThreadFactory): ExecutorServiceFactory = {
    val tf = threadFactory match {
      case m: MonitorableThreadFactory ⇒
        // add the dispatcher id to the thread names
        m.withName(m.name + "-" + id)
      case other ⇒ other
    }
    new ThreadPoolExecutorServiceFactory(tf)
  }
}

/**
 * A DSL to configure and create a MessageDispatcher with a ThreadPoolExecutor
 */
final case class ThreadPoolConfigBuilder(config: ThreadPoolConfig) {
  import ThreadPoolConfig._

  def withNewThreadPoolWithCustomBlockingQueue(newQueueFactory: QueueFactory): ThreadPoolConfigBuilder =
    this.copy(config = config.copy(queueFactory = newQueueFactory))

  def withNewThreadPoolWithCustomBlockingQueue(queue: BlockingQueue[Runnable]): ThreadPoolConfigBuilder =
    withNewThreadPoolWithCustomBlockingQueue(reusableQueue(queue))

  def withNewThreadPoolWithLinkedBlockingQueueWithUnboundedCapacity: ThreadPoolConfigBuilder =
    this.copy(config = config.copy(queueFactory = linkedBlockingQueue()))

  def withNewThreadPoolWithLinkedBlockingQueueWithCapacity(capacity: Int): ThreadPoolConfigBuilder =
    this.copy(config = config.copy(queueFactory = linkedBlockingQueue(capacity)))

  def withNewThreadPoolWithSynchronousQueueWithFairness(fair: Boolean): ThreadPoolConfigBuilder =
    this.copy(config = config.copy(queueFactory = synchronousQueue(fair)))

  def withNewThreadPoolWithArrayBlockingQueueWithCapacityAndFairness(capacity: Int, fair: Boolean): ThreadPoolConfigBuilder =
    this.copy(config = config.copy(queueFactory = arrayBlockingQueue(capacity, fair)))

  def setCorePoolSize(size: Int): ThreadPoolConfigBuilder =
    if (config.maxPoolSize < size)
      this.copy(config = config.copy(corePoolSize = size, maxPoolSize = size))
    else
      this.copy(config = config.copy(corePoolSize = size))

  def setMaxPoolSize(size: Int): ThreadPoolConfigBuilder =
    if (config.corePoolSize > size)
      this.copy(config = config.copy(corePoolSize = size, maxPoolSize = size))
    else
      this.copy(config = config.copy(maxPoolSize = size))

  def setCorePoolSizeFromFactor(min: Int, multiplier: Double, max: Int): ThreadPoolConfigBuilder =
    setCorePoolSize(scaledPoolSize(min, multiplier, max))

  def setMaxPoolSizeFromFactor(min: Int, multiplier: Double, max: Int): ThreadPoolConfigBuilder =
    setMaxPoolSize(scaledPoolSize(min, multiplier, max))

  def setKeepAliveTimeInMillis(time: Long): ThreadPoolConfigBuilder =
    setKeepAliveTime(Duration(time, TimeUnit.MILLISECONDS))

  def setKeepAliveTime(time: Duration): ThreadPoolConfigBuilder =
    this.copy(config = config.copy(threadTimeout = time))

  def setAllowCoreThreadTimeout(allow: Boolean): ThreadPoolConfigBuilder =
    this.copy(config = config.copy(allowCorePoolTimeout = allow))

  def setQueueFactory(newQueueFactory: QueueFactory): ThreadPoolConfigBuilder =
    this.copy(config = config.copy(queueFactory = newQueueFactory))

  def configure(fs: Option[Function[ThreadPoolConfigBuilder, ThreadPoolConfigBuilder]]*): ThreadPoolConfigBuilder =
    fs.foldLeft(this)((c, f) ⇒ f.map(_(c)).getOrElse(c))
}

object MonitorableThreadFactory {
  val doNothing: Thread.UncaughtExceptionHandler =
    new Thread.UncaughtExceptionHandler() { def uncaughtException(thread: Thread, cause: Throwable) = () }

  private[akka] class AkkaForkJoinWorkerThread(_pool: ForkJoinPool) extends ForkJoinWorkerThread(_pool) with BlockContext {
    override def blockOn[T](thunk: ⇒ T)(implicit permission: CanAwait): T = {
      val result = new AtomicReference[Option[T]](None)
      ForkJoinPool.managedBlock(new ForkJoinPool.ManagedBlocker {
        def block(): Boolean = {
          result.set(Some(thunk))
          true
        }
        def isReleasable = result.get.isDefined
      })
      result.get.get // Exception intended if None
    }
  }
}

final case class MonitorableThreadFactory(name: String,
                                          daemonic: Boolean,
                                          contextClassLoader: Option[ClassLoader],
                                          exceptionHandler: Thread.UncaughtExceptionHandler = MonitorableThreadFactory.doNothing,
                                          protected val counter: AtomicLong = new AtomicLong)
  extends ThreadFactory with ForkJoinPool.ForkJoinWorkerThreadFactory {

  def newThread(pool: ForkJoinPool): ForkJoinWorkerThread = {
    val t = wire(new MonitorableThreadFactory.AkkaForkJoinWorkerThread(pool))
    // Name of the threads for the ForkJoinPool are not customizable. Change it here.
    t.setName(name + "-" + counter.incrementAndGet())
    t
  }

  def newThread(runnable: Runnable): Thread = wire(new Thread(runnable, name + "-" + counter.incrementAndGet()))

  def withName(newName: String): MonitorableThreadFactory = copy(newName)

  protected def wire[T <: Thread](t: T): T = {
    t.setUncaughtExceptionHandler(exceptionHandler)
    t.setDaemon(daemonic)
    contextClassLoader foreach t.setContextClassLoader
    t
  }
}

/**
 * As the name says
 */
trait ExecutorServiceDelegate extends ExecutorService {

  def executor: ExecutorService

  def execute(command: Runnable) = executor.execute(command)

  def shutdown() { executor.shutdown() }

  def shutdownNow() = executor.shutdownNow()

  def isShutdown = executor.isShutdown

  def isTerminated = executor.isTerminated

  def awaitTermination(l: Long, timeUnit: TimeUnit) = executor.awaitTermination(l, timeUnit)

  def submit[T](callable: Callable[T]) = executor.submit(callable)

  def submit[T](runnable: Runnable, t: T) = executor.submit(runnable, t)

  def submit(runnable: Runnable) = executor.submit(runnable)

  def invokeAll[T](callables: Collection[_ <: Callable[T]]) = executor.invokeAll(callables)

  def invokeAll[T](callables: Collection[_ <: Callable[T]], l: Long, timeUnit: TimeUnit) = executor.invokeAll(callables, l, timeUnit)

  def invokeAny[T](callables: Collection[_ <: Callable[T]]) = executor.invokeAny(callables)

  def invokeAny[T](callables: Collection[_ <: Callable[T]], l: Long, timeUnit: TimeUnit) = executor.invokeAny(callables, l, timeUnit)
}

/**
 * The RejectedExecutionHandler used by Akka, it improves on CallerRunsPolicy
 * by throwing a RejectedExecutionException if the executor isShutdown.
 * (CallerRunsPolicy silently discards the runnable in this case, which is arguably broken)
 */
class SaneRejectedExecutionHandler extends RejectedExecutionHandler {
  def rejectedExecution(runnable: Runnable, threadPoolExecutor: ThreadPoolExecutor): Unit = {
    if (threadPoolExecutor.isShutdown) throw new RejectedExecutionException("Shutdown")
    else runnable.run()
  }
}