基于memcached的SNA实现

系统要集群，使用SNA方案。
一、 缓存的处理
缓存要使用统一的缓存服务器，集中式缓存。
原先的实现采用ehcache。
在spring里的配置，以资源缓存为例：

<!-- EhCache Manager -->
     <bean id="cacheManager" class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean">
         <property name="configLocation">
             <value>classpath:ehcache.xml</value>
         </property>
 </bean>

 <bean id="resourceCacheBackend"
           class="org.springframework.cache.ehcache.EhCacheFactoryBean">
         <property name="cacheManager" ref="cacheManager"/>
         <property name="cacheName" value="resourceCache"/>
     </bean>

     <bean id="resourceCache"
           class="com.framework.extcomponent.security.authentication.services.acegi.cache.EhCacheBasedResourceCache"
           autowire="byName">
         <property name="cache" ref="resourceCacheBackend"/>
     </bean>

<!-- EhCache Manager -->
    <bean id="cacheManager" class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean">
        <property name="configLocation">
            <value>classpath:ehcache.xml</value>
        </property>
</bean>

<bean id="resourceCacheBackend"
          class="org.springframework.cache.ehcache.EhCacheFactoryBean">
        <property name="cacheManager" ref="cacheManager"/>
        <property name="cacheName" value="resourceCache"/>
    </bean>

    <bean id="resourceCache"
          class="com.framework.extcomponent.security.authentication.services.acegi.cache.EhCacheBasedResourceCache"
          autowire="byName">
        <property name="cache" ref="resourceCacheBackend"/>
    </bean>

 

cacheManager负责对ehcache进行管理，初始化、启动、停止。
resourceCacheBackend负责实际执行缓存操作，put 、get、remove。
resourceCache实现具有业务语义的业务应用层面的缓存操作，内部调用resourceCacheBackend操作。

现在采用memcached。
关于客户端，采用文初封装的客户端，地址在http://code.google.com/p/memcache-client-forjava/。
使用spring的FactoryBean进行二次封装。同理：
memcachedManager负责对memcached进行管理，初始化、启动、停止。
代码：

/**
* User: ronghao
* Date: 2008-10-14
* Time: 10:36:30
* 管理Memcached 的CacheManager
*/
 public class MemcachedCacheManagerFactoryBean implements FactoryBean, InitializingBean, DisposableBean {

     protected final Log logger = LogFactory.getLog(getClass());

     private ICacheManager<IMemcachedCache> cacheManager;

     public Object getObject() throws Exception {
         return cacheManager;
    }

     public Class getObjectType() {
         return this.cacheManager.getClass();
    }

     public boolean isSingleton() {
         return true;
    }

     public void afterPropertiesSet() throws Exception {
         logger.info("Initializing Memcached CacheManager");
         cacheManager = CacheUtil.getCacheManager(IMemcachedCache.class,
                 MemcachedCacheManager.class.getName());
        cacheManager.start();
    }

     public void destroy() throws Exception {
         logger.info("Shutting down Memcached CacheManager");
        cacheManager.stop();
    }
}

/**
* User: ronghao
* Date: 2008-10-14
* Time: 10:36:30
* 管理Memcached 的CacheManager
*/
public class MemcachedCacheManagerFactoryBean implements FactoryBean, InitializingBean, DisposableBean {

    protected final Log logger = LogFactory.getLog(getClass());

    private ICacheManager<IMemcachedCache> cacheManager;

    public Object getObject() throws Exception {
        return cacheManager;
    }

    public Class getObjectType() {
        return this.cacheManager.getClass();
    }

    public boolean isSingleton() {
        return true;
    }

    public void afterPropertiesSet() throws Exception {
        logger.info("Initializing Memcached CacheManager");
        cacheManager = CacheUtil.getCacheManager(IMemcachedCache.class,
                MemcachedCacheManager.class.getName());
        cacheManager.start();
    }

    public void destroy() throws Exception {
        logger.info("Shutting down Memcached CacheManager");
        cacheManager.stop();
    }
}

 

配置：

<bean id="memcachedManager"
           class="com.framework.extcomponent.cache.MemcachedCacheManagerFactoryBean"/>

<bean id="memcachedManager"
          class="com.framework.extcomponent.cache.MemcachedCacheManagerFactoryBean"/>

 

resourceCacheBackend负责实际执行缓存操作，put 、get、remove。
代码：

/**
* User: ronghao
* Date: 2008-10-14
* Time: 10:37:16
* 返回  MemcachedCache
*/
 public class MemcachedCacheFactoryBean implements FactoryBean, BeanNameAware, InitializingBean {

     protected final Log logger = LogFactory.getLog(getClass());

     private ICacheManager<IMemcachedCache> cacheManager;
     private String cacheName;
     private String beanName;
     private IMemcachedCache cache;

     public void setCacheManager(ICacheManager<IMemcachedCache> cacheManager) {
         this.cacheManager = cacheManager;
    }

     public void setCacheName(String cacheName) {
         this.cacheName = cacheName;
    }

     public Object getObject() throws Exception {
         return cache;
    }

     public Class getObjectType() {
         return this.cache.getClass();
    }

     public boolean isSingleton() {
         return true;
    }

     public void setBeanName(String name) {
         this.beanName=name;
    }

     public void afterPropertiesSet() throws Exception {
         // If no cache name given, use bean name as cache name.
        if (this.cacheName == null) {
         this.cacheName = this.beanName;
    }
        cache = cacheManager.getCache(cacheName);
    }
}

/**
* User: ronghao
* Date: 2008-10-14
* Time: 10:37:16
* 返回  MemcachedCache
*/
public class MemcachedCacheFactoryBean implements FactoryBean, BeanNameAware, InitializingBean {

    protected final Log logger = LogFactory.getLog(getClass());

    private ICacheManager<IMemcachedCache> cacheManager;
    private String cacheName;
    private String beanName;
    private IMemcachedCache cache;

    public void setCacheManager(ICacheManager<IMemcachedCache> cacheManager) {
        this.cacheManager = cacheManager;
    }

    public void setCacheName(String cacheName) {
        this.cacheName = cacheName;
    }

    public Object getObject() throws Exception {
        return cache;
    }

    public Class getObjectType() {
        return this.cache.getClass();
    }

    public boolean isSingleton() {
        return true; 
    }

    public void setBeanName(String name) {
        this.beanName=name;
    }

    public void afterPropertiesSet() throws Exception {
        // If no cache name given, use bean name as cache name.
       if (this.cacheName == null) {
		this.cacheName = this.beanName;
	}
        cache = cacheManager.getCache(cacheName);
    }
}

 

配置：

<bean id="resourceCacheBackend"
           class="com.framework.extcomponent.cache.MemcachedCacheFactoryBean">
         <property name="cacheManager" ref="memcachedManager"/>
         <property name="cacheName" value="memcache"/>
     </bean>

<bean id="resourceCacheBackend"
          class="com.framework.extcomponent.cache.MemcachedCacheFactoryBean">
        <property name="cacheManager" ref="memcachedManager"/>
        <property name="cacheName" value="memcache"/>
    </bean>

 

resourceCache同上，替换新的实现类MemcachedBasedResourceCache即可。

二、 Session失效的处理
采用memcached作为httpsession的存储，并不直接保存httpsession对象，自定义SessionMap，SessionMap直接继承HashMap，保存SessionMap。

会话胶粘：未失败转发的情况下没必要在memcached保存的SessionMap和httpsession之间复制来复制去，眉来眼去。

利用memcached计数器保存在线人数。

系统权限采用了acegi，在acegi的拦截器链里配置snaFilter

<bean id="filterChainProxy"
           class="org.acegisecurity.util.FilterChainProxy">
         <property name="filterInvocationDefinitionSource">
             <value>
                CONVERT_URL_TO_LOWERCASE_BEFORE_COMPARISON
                PATTERN_TYPE_APACHE_ANT
                /**=snaFilter,httpSessionContextIntegrationFilter,logoutFilter,authenticationProcessingFilter,basicProcessingFilter,securityContextHolderAwareRequestFilter,exceptionTranslationFilter,filterInvocationInterceptor
             </value>
         </property>
 </bean>

<bean id="filterChainProxy"
          class="org.acegisecurity.util.FilterChainProxy">
        <property name="filterInvocationDefinitionSource">
            <value>
                CONVERT_URL_TO_LOWERCASE_BEFORE_COMPARISON
                PATTERN_TYPE_APACHE_ANT
                /**=snaFilter,httpSessionContextIntegrationFilter,logoutFilter,authenticationProcessingFilter,basicProcessingFilter,securityContextHolderAwareRequestFilter,exceptionTranslationFilter,filterInvocationInterceptor
            </value>
        </property>
</bean>

 

注意需要配置在第一个。
snaFilter的职责：
1、 没有HttpSession时，创建HttpSession;
2、 创建Cookie保存HttpSession id;
3、 如果Cookie保存的HttpSession id与当前HttpSession id一致，说明是正常请求；
4、 如果Cookie保存的HttpSession id与当前HttpSession id不一致，说明是失败转发；失败转发的处理：
     4.1、根据Cookie保存的HttpSession id从memcached获取SessionMap；
     4.2、SessionMap属性复制到当前HttpSession；
     4.3、memcached删除SessionMap。
5、 判断当前请求url是否是登出url，是则删除SessionMap，在线人数减1.

代码：

public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
                          FilterChain filterChain) throws IOException, ServletException {
         final HttpServletRequest hrequest = (HttpServletRequest) servletRequest;
         final HttpServletResponse hresponse = (HttpServletResponse) servletResponse;
        String uri = hrequest.getRequestURI();
         logger.debug("开始SNA拦截-----------------" + uri);
        HttpSession httpSession = hrequest.getSession();
        String sessionId = httpSession.getId();
         //如果是登出,则直接干掉sessionMap
         if (uri.equals(logoutUrl)) {
             logger.debug("remove sessionmap:" + sessionId);
             //在线人数减1
             getCache().addOrDecr("userCount",1);
            getCache().remove(sessionId);
         } else {
            String cookiesessionid = getSessionIdFromCookie(hrequest, hresponse);
             if (!sessionId.equals(cookiesessionid)) {
                createCookie(sessionId, hresponse);
                SessionMap sessionMap = getSessionMap(cookiesessionid);
                 if (sessionMap != null) {
                     logger.debug("fail over--------sessionid:" + sessionId + "cookiesessionid:" + cookiesessionid);
                    initialHttpSession(sessionMap, httpSession);
                    cache.remove(cookiesessionid);
                }
            }
        }
        filterChain.doFilter(hrequest, hresponse);
}

public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
                         FilterChain filterChain) throws IOException, ServletException {
        final HttpServletRequest hrequest = (HttpServletRequest) servletRequest;
        final HttpServletResponse hresponse = (HttpServletResponse) servletResponse;
        String uri = hrequest.getRequestURI();
        logger.debug("开始SNA拦截-----------------" + uri);
        HttpSession httpSession = hrequest.getSession();
        String sessionId = httpSession.getId();
        //如果是登出,则直接干掉sessionMap
        if (uri.equals(logoutUrl)) {
            logger.debug("remove sessionmap:" + sessionId);
            //在线人数减1
            getCache().addOrDecr("userCount",1);
            getCache().remove(sessionId);
        } else {
            String cookiesessionid = getSessionIdFromCookie(hrequest, hresponse);
            if (!sessionId.equals(cookiesessionid)) {
                createCookie(sessionId, hresponse);
                SessionMap sessionMap = getSessionMap(cookiesessionid);
                if (sessionMap != null) {
                    logger.debug("fail over--------sessionid:" + sessionId + "cookiesessionid:" + cookiesessionid);
                    initialHttpSession(sessionMap, httpSession);
                    cache.remove(cookiesessionid);
                }
            }
        }
        filterChain.doFilter(hrequest, hresponse);
}

 

利用HttpSessionAttributeListener监听httpsession的属性变化,同步到memecached中的sessionmap。

public void attributeAdded(HttpSessionBindingEvent event) {
        HttpSession httpSession = event.getSession();
        String attrName = event.getName();
        Object attrValue = event.getValue();
        String sessionId = httpSession.getId();
         logger.debug("attributeAdded sessionId:" + sessionId + "name:" + attrName + ",value:" + attrValue);
        SessionMap sessionMap = getSessionMap(sessionId);
         if (sessionMap == null){
             //在线人数加1
             getCache().addOrIncr("userCount",1);
             sessionMap = new SessionMap();
        }
         logger.debug("name:" + attrName + ",value:" + attrValue);
        sessionMap.put(attrName, attrValue);
        getCache().put(sessionId, sessionMap);
    }

     public void attributeRemoved(HttpSessionBindingEvent event) {
        HttpSession httpSession = event.getSession();
        String attrName = event.getName();
        String sessionId = httpSession.getId();
         logger.debug("attributeRemoved sessionId:" + sessionId + "name:" + attrName);
        SessionMap sessionMap = getSessionMap(sessionId);
         if (sessionMap != null) {
             logger.debug("remove:" + attrName);
            sessionMap.remove(attrName);
            getCache().put(sessionId, sessionMap);
        }
    }

     public void attributeReplaced(HttpSessionBindingEvent event) {
        attributeAdded(event);
    }

public void attributeAdded(HttpSessionBindingEvent event) {
        HttpSession httpSession = event.getSession();
        String attrName = event.getName();
        Object attrValue = event.getValue();
        String sessionId = httpSession.getId();
        logger.debug("attributeAdded sessionId:" + sessionId + "name:" + attrName + ",value:" + attrValue);
        SessionMap sessionMap = getSessionMap(sessionId);
        if (sessionMap == null){
            //在线人数加1
            getCache().addOrIncr("userCount",1);
            sessionMap = new SessionMap();
        }
        logger.debug("name:" + attrName + ",value:" + attrValue);
        sessionMap.put(attrName, attrValue);
        getCache().put(sessionId, sessionMap);
    }

    public void attributeRemoved(HttpSessionBindingEvent event) {
        HttpSession httpSession = event.getSession();
        String attrName = event.getName();
        String sessionId = httpSession.getId();
        logger.debug("attributeRemoved sessionId:" + sessionId + "name:" + attrName);
        SessionMap sessionMap = getSessionMap(sessionId);
        if (sessionMap != null) {
            logger.debug("remove:" + attrName);
            sessionMap.remove(attrName);
            getCache().put(sessionId, sessionMap);
        }
    }

    public void attributeReplaced(HttpSessionBindingEvent event) {
        attributeAdded(event);
    }

 

利用HttpSessionListener，sessionDestroyed事件时根据sessionid删除memcached里的sessionMap（如果存在）。不再担心httpsession的过期问题。

public void sessionDestroyed(HttpSessionEvent event) {
        HttpSession httpSession = event.getSession();
        String sessionId = httpSession.getId();
         logger.debug("session Removed sessionId:" + sessionId);
        SessionMap sessionMap = getSessionMap(sessionId);
         if (sessionMap != null) {
             logger.debug("remove sessionmap:" + sessionId);
             //在线人数减1
             getCache().addOrDecr("userCount",1);
            getCache().remove(sessionId);
        }
    }

public void sessionDestroyed(HttpSessionEvent event) {
        HttpSession httpSession = event.getSession();
        String sessionId = httpSession.getId();
        logger.debug("session Removed sessionId:" + sessionId);
        SessionMap sessionMap = getSessionMap(sessionId);
        if (sessionMap != null) {
            logger.debug("remove sessionmap:" + sessionId);
            //在线人数减1
            getCache().addOrDecr("userCount",1);
            getCache().remove(sessionId);
        }
    }

 

三、 文件保存的处理
和缓存类似，采用集中式的文件服务。对于linux，采用nfs。参考文档http://linux.vbird.org/linux_server/0330nfs.php#What_NFS_perm。关键在于对权限的分配。
应用程序本身不用修改。