yarn状态机可视化

YARN中实现了多个状态机对象，包括ResourceManager中的RMAppImpl、RMApp-AttemptImpl、RMContainerImpl和RMNodeImpl，NodeManager中的ApplicationImpl、ContainerImpl和LocalizedResource，MRAppMaster中的JobImpl、TaskImpl和TaskAttemptImpl等。为了便于用户查看这些状态机的状态变化以及相关事件，YARN提供了一个状态机可视化工具，具体操作步骤如下。
步骤1　将状态机转化为graphviz(.gv)格式的文件，在源代码根目录下执行编译命令如下：
mvn compile -Pvisualize
经过该步骤后，本地目录中生成了ResourceManager.gv、NodeManager.gv和MapReduce.gv三个graphviz格式的文件。NodeManager.gv文件中LocalizedResource状态机部分内容如下：

subgraph cluster_LocalizedResource {
label="LocalizedResource"
"LocalizedResource.FAILED" [ label = FAILED ];
"LocalizedResource.DOWNLOADING" [ label = DOWNLOADING ];
"LocalizedResource.DOWNLOADING" -> "LocalizedResource.DOWNLOADING" [ label = "REQUEST,\nRELEASE" ];
"LocalizedResource.DOWNLOADING" -> "LocalizedResource.FAILED" [ label = "LOCALIZATION_FAILED" ];
"LocalizedResource.DOWNLOADING" -> "LocalizedResource.LOCALIZED" [ label = "LOCALIZED" ];
"LocalizedResource.INIT" [ label = INIT ];
"LocalizedResource.INIT" -> "LocalizedResource.DOWNLOADING" [ label = "REQUEST" ];
"LocalizedResource.LOCALIZED" [ label = LOCALIZED ];
"LocalizedResource.LOCALIZED" -> "LocalizedResource.LOCALIZED" [ label = "REQUEST,\nRELEASE" ];
}

步骤2　使用可视化包graphviz中的相关命令生成状态机图，Shell命令具体如下：
dot -Tpng NodeManager.gv > NodeManager.png
如果尚未安装graphviz包，操作该步骤之前先要安装该包，cent os安装命令如下：
sudo yum install graphviz

打开NodeManager.png，如下图所示(为了便于展示，分拆成了两个图)：