Spark LiveListenerBus

开启四个事件处理队列：

private[scheduler] val SHARED_QUEUE = "shared"

  private[scheduler] val APP_STATUS_QUEUE = "appStatus"

  private[scheduler] val EXECUTOR_MANAGEMENT_QUEUE = "executorManagement"

  private[scheduler] val EVENT_LOG_QUEUE = "eventLog"

每个队列单独一个线程处理。