Apache Hadoop 2.2.0 (2013年10月发布通告）



Apache Hadoop 2.2.0

Apache Hadoop 2.2.0 consists of significant improvements over the previous stable release (hadoop-1.x).

和上一个的稳定版 (hadoop-1.x)相比，Hadoop 2.2.0有大量的改进（显著的提高）

Here is a short overview of the improvments to both HDFS and MapReduce.

以下为Hadoop在HDFS和MapReduce方面各项改进的简短总结：

In order to scale the name service horizontally, federation uses multiple independent Namenodes/Namespaces. The Namenodes are federated, that is, the Namenodes are independent and don't require coordination with each other. The datanodes are used as common
storage for blocks by all the Namenodes. Each datanode registers with all the Namenodes in the cluster. Datanodes send periodic heartbeats and block reports and handles commands from the Namenodes.
为了横向扩展命名服务（Name Service）, federation 使用了多重独立的命名结点/命名空间（Namenodes/Namespaces）。 命名结点被联合起来，就是说，命名结点是自主的，互不依靠，结点之间不需要相互协调。 数据结点被所有命名结点用做blocks(文件块）的公用存储设备。所有的数据结点在Hadoop集群中的所有命名结点中注册。数据结点从命名结点中周期性地发送心跳（heartbeats）和文件块（blocks）报告。

More details are available in the
HDFS Federation document.

欲知更多细节，请阅读HDFS Federation （HDFS联盟）文档。

The new architecture introduced in hadoop-0.23, divides the two major functions of the JobTracker: resource management and job life-cycle management into separate components.

hadoop-0.23中引入了新的架构，JobTracker(作业跟踪器）的两个主要功能分成两个部分： 资源管理和作业生命周期管理，现在它们各为独立的组件。

The new ResourceManager manages the global assignment of compute resources to applications and the per-application ApplicationMaster manages the application‚Äôs scheduling and coordination. (本段原文有错误）

新的ResourceManager (资源管理器)管理应用程序们的计算资源的全局任务，各应用程序的ApplicationMaster（应用大师）管理应用程序调度和协调

An application is either a single job in the sense of classic MapReduce jobs or a DAG of such jobs.

一个应用程序可以是一个单一的作业--可以理解为经典的MapReduce作业， 也可以是DAG这样的作业。

The ResourceManager and per-machine NodeManager daemon, which manages the user processes on that machine, form the computation fabric.

ResourceManager和各机器上的结点管理器（NodeManager）工具（该工具管理那台机器上的用户进程）形成计算结构体（computation fabric译成什么更好）。

The per-application ApplicationMaster is, in effect, a framework specific library and is tasked with negotiating resources from the ResourceManager and working with the NodeManager(s) to execute and monitor the tasks.

事实上，各应用程序的ApplicationMaster是一个特殊的框架库，ApplicationMaster负责从资源管理器那里商定资源，并和一个或多个结点管理器一起工作，来执行或监视所有的任务。

More details are available in the
YARN document.

欲知更多细节，请见YARN文档。

Getting Started准备开工：

The Hadoop documentation includes the information you need to get started using Hadoop. Begin with theSingle Node Setup
which shows you how to set up a single-node Hadoop installation. Then move on to theCluster Setup to learn how to set up
a multi-node Hadoop installation.

Hadoop文档包括所有你需要的开始使用Hadoop所要掌握的信息。 从单结点安装设置（演示如何建立一个单结点的安装过程）开始，然后接下来到集群设置，学会如何建立多结点Hadoop安装。

(周六晨起无事，看看hadoop2有什么新花样，译给自已看的，放在这里留个记录，2014-01-11 11:24am 多伦多）