Valor InheritableThreadLocal não herdado pelos threads ExecutorService

Question

Dec 23, 2016, 01:10 AM

Valor InheritableThreadLocal não herdado pelos threads ExecutorService

import java.util.concurrent.Executors
import scala.concurrent.{ExecutionContext, Future}

object TestInheritableThreadLocal {

  def main(args: Array[String]): Unit = {

    implicit val ec = ExecutionContext.fromExecutor(Executors.newFixedThreadPool(2))

    val tl: InheritableThreadLocal[String] = new InheritableThreadLocal[String]()
    tl.set("InitialValue")

    Future {
      println("111 " + Thread.currentThread() + tl.get())
      Future {
        println("222 " + Thread.currentThread() + tl.get())
      }
    }
    Thread.sleep(3000)

    Future {
      tl.set("NewInitialValue")
      println("333 " + Thread.currentThread() + tl.get())
      Future {
        println("444 " + Thread.currentThread() + tl.get())
      }
      Thread.sleep(3000)
    }
  }
}

Resultado

111 Thread[pool-1-thread-1,5,main]InitialValue
222 Thread[pool-1-thread-2,5,main]InitialValue
333 Thread[pool-1-thread-1,5,main]NewInitialValue
444 Thread[pool-1-thread-2,5,main]InitialValue

Eu estava esperando "NewInitialValue" na última linha de saída desde que o 333 Thread gerou o Thread 444 e tl é um local herdável do thread.

O que está causando esse problema e como ele pode ser resolvido?