*/
  private fun promoteAndExecute(): Boolean {
    lock.assertNotHeld()

    val executableCalls = mutableListOf<AsyncCall>()
    val isRunning: Boolean
    this.withLock {
      val i = readyAsyncCalls.iterator()
      while (i.hasNext()) {
        val asyncCall = i.next()

        if (runningAsyncCalls.size >= this.maxRequests) break // Max capacity.