CODEWITHSUNDEEP
scalaakkathreadpool
Atiq
Atiq

Reputation: 396

Akka execution context vs Future global context

I know basic difference between the Akka dispatcher vs Global Execution context.

I tried this code with scala.concurrent.ExecutionContext.Implicits.global

import scala.concurrent.ExecutionContext.Implicits.global
  val resultF = (0 to 100).map(
    x =>
      Future {
        val startTime = System.currentTimeMillis()
        val task = Future {
          Thread.sleep(100)
          x
        }
        task.onSuccess {
          case result =>
            val timeRemaining = System.currentTimeMillis() - startTime
            println(s"$result $timeRemaining")
        }
    }
  )
  StdIn.readLine()

The Above code prints on an average the time equal to Thread.sleep(), around 103 milliseconds on an average.

However following code prints the time taken between 100-400 millisecond.

  val system = ActorSystem("test")
  implicit val executionContext = system.dispatcher
  val resultF = (0 to 100).map(
    x =>
      Future {
        val startTime = System.currentTimeMillis()
        val task = Future {
          Thread.sleep(100)
          x
        }
        task.onSuccess {
          case result =>
            val timeRemaining = System.currentTimeMillis() - startTime
            println(s"$result $timeRemaining")
        }
    }
  )
  StdIn.readLine()

I'm failing to understand what's the major difference apart from thread-pool used.

Upvotes: 2

Views: 3066

Answers (1)

Rich
Rich

Reputation: 15464

I'm failing to understand what's the major difference apart from thread-pool used.

The only difference is the thread pools used and their work scheduling algorithms.

The Akka ActorSystem threadpool is a fork-join executor, as described at http://doc.akka.io/docs/akka/2.5/scala/dispatchers.html

The "global" default ExecutionContext is a work-stealing thread pool, see e.g. https://github.com/scala/scala/blob/v2.12.3/src/library/scala/concurrent/ExecutionContext.scala#L135

See e.g. How is the fork/join framework better than a thread pool?

Upvotes: 3

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