sqoop导数据卡住在INFO mapreduce.Job: Running job: job_1447835049223_0010
查yarn日志全是：
INFO org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CapacityScheduler: Null container completed...解决方法：
http://stackoverflow.com/questions/28294684/hadoop-2-6-0-does-not-work-reduce-tasks-in-wordcount-example
The answer is not enough memory. Every container of task (map or reduce), was too big for my machines.
