After running my small application for Spark of Machine Learning , the job hangs and the Spark UI for it display nothing for more than 5 minutes.
That is weird and I see some logs in UI of yarn:

16/09/30 17:05:33 INFO ipc.Client: Retrying connect to server: user/110.75.167.140:8020. Already tried 0 time(s); maxRetries=45
16/09/30 17:05:53 INFO ipc.Client: Retrying connect to server: user/110.75.167.140:8020. Already tried 1 time(s); maxRetries=45
16/09/30 17:06:13 INFO ipc.Client: Retrying connect to server: user/110.75.167.140:8020. Already tried 2 time(s); maxRetries=45
16/09/30 17:06:33 INFO ipc.Client: Retrying connect to server: user/110.75.167.140:8020. Already tried 3 time(s); maxRetries=45
16/09/30 17:06:53 INFO ipc.Client: Retrying connect to server: user/110.75.167.140:8020. Already tried 4 time(s); maxRetries=45
16/09/30 17:07:13 INFO ipc.Client: Retrying connect to server: user/110.75.167.140:8020. Already tried 5 time(s); maxRetries=45
16/09/30 17:07:33 INFO ipc.Client: Retrying connect to server: user/110.75.167.140:8020. Already tried 6 time(s); maxRetries=45

I haven’t any IP looks like “110.75.x.x”. Why is the Spark job trying to connect it ?
After reviewing the code carefully, I find out the problem:

    val conf = new SparkConf().setAppName("Simple Regression")
    val sc = new SparkContext(conf)

    val smsData = sc.textFile("hdfs://user/sanbai/SMSSpamCollection")

It is me who forget to add IP to URI of HDFS. Thus, the correct code should be:

    val smsData = sc.textFile("hdfs://127.0.0.1/user/sanbai/SMSSpamCollection")

Now the application runs correctly.