/** Returns a snapshot of the calls currently being executed. */
  @Synchronized
  fun runningCalls(): List<Call> = (runningSyncCalls + runningAsyncCalls.map { it.call }).unmodifiable()

  @Synchronized
  fun queuedCallsCount(): Int = readyAsyncCalls.size

  @Synchronized
  fun runningCallsCount(): Int = runningAsyncCalls.size + runningSyncCalls.size

  @JvmName("-deprecated_executorService")
  @Deprecated(