最近在使用Spark做一些测试，将代码打包好后，使用Spark-Submit提交任务时，一直报错：

16/01/07 13:50:16 INFO SparkContext: Added JAR file:/root/sparkonhbase.jar at http://10.10.12.1:55234/jars/sparkonhbase.jar with timestamp 1452145816037
16/01/07 13:50:16 WARN MetricsSystem: Using default name DAGScheduler for source because spark.app.id is not set.
16/01/07 13:50:16 INFO AppClient$ClientEndpoint: Connecting to master spark://10.10.12.1:7077...
16/01/07 13:50:36 ERROR SparkUncaughtExceptionHandler: Uncaught exception in thread Thread[appclient-registration-retry-thread,5,main]
java.util.concurrent.RejectedExecutionException: Task java.util.concurrent.FutureTask@116465dc rejected from java.util.concurrent.ThreadPoolExecutor@565b576f[Running, pool size = 1, active threads = 1, queued tasks = 0, completed tasks = 0]
	at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2048)
	at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:821)
	at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1372)
	at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:110)
	at org.apache.spark.deploy.client.AppClient$ClientEndpoint$$anonfun$tryRegisterAllMasters$1.apply(AppClient.scala:96)
	at org.apache.spark.deploy.client.AppClient$ClientEndpoint$$anonfun$tryRegisterAllMasters$1.apply(AppClient.scala:95)
	at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
	at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
	at scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:33)
	at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:108)
	at scala.collection.TraversableLike$class.map(TraversableLike.scala:244)
	at scala.collection.mutable.ArrayOps$ofRef.map(ArrayOps.scala:108)
	at org.apache.spark.deploy.client.AppClient$ClientEndpoint.tryRegisterAllMasters(AppClient.scala:95)
	at org.apache.spark.deploy.client.AppClient$ClientEndpoint.org$apache$spark$deploy$client$AppClient$ClientEndpoint$$registerWithMaster(AppClient.scala:121)
	at org.apache.spark.deploy.client.AppClient$ClientEndpoint$$anon$2$$anonfun$run$1.apply$mcV$sp(AppClient.scala:132)
	at org.apache.spark.util.Utils$.tryOrExit(Utils.scala:1119)
	at org.apache.spark.deploy.client.AppClient$ClientEndpoint$$anon$2.run(AppClient.scala:124)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
	at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:304)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:745)
16/01/07 13:50:36 INFO DiskBlockManager: Shutdown hook called
16/01/07 13:50:36 INFO ShutdownHookManager: Shutdown hook called

     但是，我运行官方提供的Example时，就能成功执行，百思不得其解！后来，终于在http://www.cnblogs.com/zhangqingping/p/4354383.html 这一篇文章上得到了答案，原来:

      Spark使用了Akka,Spark的master URL里面必须使用hostname,不能直接使用IP，否则会报错。怎么听着好低级的错误啊！抱着试一试的态度，我讲代码里的master的IP改成了所对应的hostname，再次打包，提交，果然能运行了！

     但是，为什么Spark,Akka居然连这种问题都不能解决呢？期待高手解答，先在此备忘解决方法。