Dose spark auto invoke StreamingContext.stop while receive kill signal?

[Bin Wang]

I'd like the spark application to be stopped gracefully while received kill
signal, so I add these code:

    sys.ShutdownHookThread {
      println("Gracefully stopping Spark Streaming Application")
      ssc.stop(stopSparkContext = true, stopGracefully = true)
      println("Application stopped")
    }

But the application is not stopped gracefully:

15/09/23 17:44:38 ERROR yarn.ApplicationMaster: RECEIVED SIGNAL 15: SIGTERM
...
15/09/23 17:44:38 INFO streaming.StreamingContext: Invoking
stop(stopGracefully=false) from shutdown hook

Dose spark auto invoke StreamingContext.stop for me?