说明：  《Hadoop 开发者》第四期，在千呼万呼中，终于艰难的出来。这是众多Hadoopor期望的一期，也是相对成熟的一期，本期的作者大多都具备在一线的Hadoop 开发或应用经验，因此实践性较强。
(" Hadoop developers" Fourth, in the thousand million calls in the call finally came out hard. This is one of many Hadoopor expected, is relatively mature one, mostly with the current period in the forefront of the development or application of Hadoop experience, so practice is strong.)