Hadoop??streaming

Hello??we know Hadoop-streaming is use for Hadoop to run native program. Hadoop-streaming supports Map and Reduce logic. Reduce logic means Hadoop collect all values with same key and give the stream for the native application.Spark has PipeRDD too, but PipeRDD doesn't support Reduce logic. So

How to start history tracking URL

I run spark client on yarn, and use "history-daemon.sh start historyserver" to start tracking the hisotory URL,but it didn't work, why?