<实践>Voldemort与Objot集成的WAP高性能方案与简单实现（一）

［摘要］

Voldemort：高性能、高扩展性、不错的一致性Key-Value集群方案，目前被LinkIn使用，与Dynamo思想类似，参见http://project-voldemort.com
Objot：面向服务的轻量级web开发库，参见http://objot.com

［目标］

搭建一个WAP游戏开发框架，利用烂服务器集群提供高性能，尽量保证游戏数据的一致性，并可根据负载情况随时进行扩展，同时能够通过配置来调节各服务器利用率。
尽可能减少网络传输，单服务器既包含WEB也包含DB节点。

［技术选型］

1、游戏中不需要复杂的查询，因此抛弃了SQL数据库而使用Key-Value存储；通过对各种数据库的了解，发现Voldemort更适合，能保证目标。采用其Server Routing模式，不将WEB与DB在物理上划开。
2、Spring过于臃肿，故采用更加轻量级的Objot，同时Objot基于Java5，配置更简洁。
3、采用JSTL ＋ JSP处理页面数据。
4、采用Tomcat作为WEB容器。


［实现］（以单数据库节点为例）
1、在Servlet中启动Voldemort服务器
cluster.xml //Voldemort集群配置文件

<cluster>
	<name>vortex</name>
	<server>
		<id>0</id>
		<host>localhost</host>
		<http-port>8081</http-port>
		<socket-port>6666</socket-port>
		<partitions>0, 1</partitions>
	</server>
</cluster>

server.properties //Voldemort节点服务器配置

# The ID of *this* particular cluster node
node.id=0

max.threads=100

############### DB options ######################
#不需要HTTP服务，Server Routing Mode必须开启socket
http.enable=false
socket.enable=true

# 采用BDB存储
bdb.write.transactions=false
bdb.flush.transactions=false
bdb.cache.size=256M

#NIO connector settings.
enable.nio.connector=false

storage.configs=voldemort.store.bdb.BdbStorageConfiguration, voldemort.store.readonly.ReadOnlyStorageConfiguration

stores.xml //存储方式配置

<stores>
  <store>
    <name>vortex</name>
    <persistence>bdb</persistence>
    <routing>server</routing>
    <replication-factor>1</replication-factor>
    <required-reads>1</required-reads>
    <required-writes>1</required-writes>
    <key-serializer>
      <type>identity</type>
    </key-serializer>
    <value-serializer>
      <type>identity</type>
    </value-serializer>
  </store>
</stores>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app>
...
	<servlet>
		<servlet-name>vortex-servlet</servlet-name>
		<servlet-class>vortex.VortexServlet</servlet-class>
                <!-- Voldemort家目录：）-->
		<init-param>
			<param-name>voldemort-home</param-name>
			<param-value>/home/nkadun/vortex/voldemort</param-value>
		</init-param>
		<load-on-startup>0</load-on-startup>
	</servlet>
	
	<servlet-mapping>
		<servlet-name>vortex-servlet</servlet-name>
		<url-pattern>/service/*</url-pattern>
	</servlet-mapping>
...
</web-app>

VortexServlet.java

public class VortexServlet implements Servlet {
	...
	private final String VOLDEMORT_HOME_KEY = "voldemort-home";
	private VoldemortServer server;
	private StoreRepository respository;

	private ServiceHandler handler;

	@Override
	public void destroy() {
		logger.info("Shutdown voldemort server...");
		if(server != null)
			server.stop();
		logger.info("Shutdown voldemort server successfully.");
	}
	@Override
	public void init(ServletConfig c) throws ServletException {
		config = c;
		handler = new ServiceHandler();
		try {
			logger.info("Starting voldemort server...");
			String voldemortHome = c.getInitParameter(VOLDEMORT_HOME_KEY);
			server = new VoldemortServer(VoldemortConfig.loadFromVoldemortHome(voldemortHome));
//启动Voldemort服务器
			server.start();
			respository = ((StorageService)server.getService(ServiceType.STORAGE)).getStoreRepository();
			logger.info("Voldemort server started.");

			handler.init(respository);
		}
		catch(ConfigurationException e) {
			logger.info("Error occurred:", e);
			throw e;
		}
		catch(Exception e) {
			logger.error("Error occurred:", e);
			throw new ServletException(e);
		}
	}

	@Override
	public void service(ServletRequest request, ServletResponse response) throws ServletException, IOException {
		try {
			String page = handler.handle(request, response);
			forward(page, request, response);
		}
		catch(Exception e) {
			throw new ServletException(e);
		}
	}
...
}