DatanodeDescriptor类图描述

本想画个UML里的标准类图的，可惜linux下的画图工具都不那么好使，然后装了xmind，发现用这个画也还可以，就是每次图的位置不好定。

 这里涉及到的其他类将在单独的blog里分析，因为整个图实在太大了，我发现用xmind搞的美观而且还方便记忆。

 

光有图还不能说清他们的具体功能，故增加点文字描述信息

 

    Node

/** The interface defines a node in a network topology.
 * A node may be a leave representing a data node or an inner
 * node representing a datacenter or rack.
 * Each data has a name and its location in the network is
 * decided by a string with syntax similar to a file name. 
 * For example, a data node's name is hostname:port# and if it's located at
 * rack "orange" in datacenter "dog", the string representation of its
 * network location is /dog/orange
 */

 

   DatanodeID

 

/**
 * DatanodeID is composed of the data node 
 * name (hostname:portNumber) and the data storage ID, 
 * which it currently represents.
 * 
 */

 

   DatanodeInfo

 

/** 
 * DatanodeInfo represents the status of a DataNode.
 * This object is used for communication in the
 * Datanode Protocol and the Client Protocol.
 */

 

    DatanodeDescriptor

 

/**************************************************
 * DatanodeDescriptor tracks stats on a given DataNode,
 * such as available storage capacity, last update time, etc.,
 * and maintains a set of blocks stored on the datanode. 
 *
 * This data structure is a data structure that is internal
 * to the namenode. It is *not* sent over-the-wire to the Client
 * or the Datnodes. Neither is it stored persistently in the
 * fsImage.

 **************************************************/