基于Redis的CAS集群

2015/06/14 22:46
阅读数 855

单点登录(SSO)是复杂应用系统的基本需求,Yale CAS是目前常用的开源解决方案。CAS认证中心,基于其特殊作用,自然会成为整个应用系统的核心,所有应用系统的认证工作,都将请求到CAS来完成。因此CAS服务器是整个应用的关键节点,CAS发生故障,所有系统都将陷入瘫痪。同时,CAS的负载能力要足够强,能够承担所有的认证请求响应。利用负载均衡和集群技术,不仅能克服CAS单点故障,同时将认证请求分布到多台CAS服务器上,有效减轻单台CAS服务器的请求压力。下面将基于CAS 3.4.5来讨论下CAS集群。

CAS的工作原理,主要是基于票据(Ticket)来实现的(参见 CAS基本原理)。CAS票据,存储在TicketRegistry中,因此要想实现CAS Cluster, 必须要多台CAS之间共享所有的Ticket,采用统一的TicketRegistry,可以达到此目的。  缺省的CAS实现中,TicketRegistry在内存中实现,不同的CAS服务器有自己单独的TicketRegistry,因此是不支持分布式集群的。但CAS提供了支持TicketRegistry分布式的接口org.jasig.cas.ticket.registry.AbstractDistributedTicketRegistry,我们可以实现这个接口实现多台CAS服务器TicketRegistry共享,从而实现CAS集群。

同时,较新版本CAS使用SpringWebFlow作为认证流程,而webflow需要使用session存储流程相关信息,因此实现CAS集群,我们还得需要让不同服务器的session进行共享。

我们采用内存数据库Redis来实现TicketRegistry,让多个CAS服务器共用同一个TicketRegistry。同样方法,我们让session也存储在Redis中,达到共享session的目的。下面就说说如何用Redis来实现TicketRegistry,我们使用Java调用接口Jedis来操作Redis,代码如下:

 

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Collection;

import org.jasig.cas.ticket.Ticket;
import org.jasig.cas.ticket.TicketGrantingTicket;
import org.jasig.cas.ticket.registry.AbstractDistributedTicketRegistry;


import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;


/*
 *  TicketRegistry using Redis, to solve CAS Cluster.
 *  
 *  @author ZL
 * 
 */

public class RedisTicketRegistry extends AbstractDistributedTicketRegistry {

	
	private static int redisDatabaseNum;
	private static String hosts;
	private static int port;
         private static int st_time;  //ST最大空闲时间
          private static int tgt_time; //TGT最大空闲时间
    
	private static JedisPool cachePool;
	
	static {
	
		redisDatabaseNum = PropertiesConfigUtil.getPropertyInt("redis_database_num");
		hosts = PropertiesConfigUtil.getProperty("hosts");
		port = PropertiesConfigUtil.getPropertyInt("port");
		st_time = PropertiesConfigUtil.getPropertyInt("st_time");
		tgt_time = PropertiesConfigUtil.getPropertyInt("tgt_time");
		cachePool = new JedisPool(new JedisPoolConfig(), hosts, port);
		
	}
	
	public void addTicket(Ticket ticket) {
			
		Jedis jedis = cachePool.getResource();
		jedis.select(redisDatabaseNum);
		
                  int seconds = 0;

                  String key = ticket.getId() ;
		
		if(ticket instanceof TicketGrantingTicket){
			//key = ((TicketGrantingTicket)ticket).getAuthentication().getPrincipal().getId();
			seconds = tgt_time/1000;
		}else{
			seconds = st_time/1000;
		}
  
		
	    ByteArrayOutputStream bos = new ByteArrayOutputStream();
	    ObjectOutputStream oos = null;
	    try{
		    oos = new ObjectOutputStream(bos);
		    oos.writeObject(ticket);
		   
	    }catch(Exception e){
	    	log.error("adding ticket to redis error.");
	    }finally{
	    	try{ 
	    		if(null!=oos) oos.close();
	    	}catch(Exception e){
	    		log.error("oos closing error when adding ticket to redis.");
	    	}
	    }
	    jedis.set(key.getBytes(), bos.toByteArray());
		jedis.expire(key.getBytes(), seconds);
		
		cachePool.returnResource(jedis);
		
	}
	
    public Ticket getTicket(final String ticketId) {
        return getProxiedTicketInstance(getRawTicket(ticketId));
    }
	
	
    private Ticket getRawTicket(final String ticketId) {
		
    	if(null == ticketId) return null;
    	
    	Jedis jedis = cachePool.getResource();
		jedis.select(redisDatabaseNum);
		
		Ticket ticket = null;
        
        ByteArrayInputStream bais = new ByteArrayInputStream(jedis.get(ticketId.getBytes()));
		ObjectInputStream ois = null;
		
		try{
			ois = new ObjectInputStream(bais);
			ticket = (Ticket)ois.readObject(); 
		}catch(Exception e){
			log.error("getting ticket to redis error.");
		}finally{
			try{
				if(null!=ois)  ois.close();
			}catch(Exception e){
				log.error("ois closing error when getting ticket to redis.");
			}
		}
        
		cachePool.returnResource(jedis);
		
		return ticket;
    }
   
    

    public boolean deleteTicket(final String ticketId) {
        
        if (ticketId == null) {
            return false;
        }
        
        
		Jedis jedis = cachePool.getResource();
		jedis.select(redisDatabaseNum);
			
		jedis.del(ticketId.getBytes());
	    
        cachePool.returnResource(jedis);
        
        return true;        
    }
 
	public Collection<Ticket> getTickets() {
		
		throw new UnsupportedOperationException("GetTickets not supported.");

	}

    protected boolean needsCallback() {
        return false;
    }
    
    protected void updateTicket(final Ticket ticket) {
        addTicket(ticket);
    }
 
}


同时,我们在ticketRegistry.xml配置文件中,将TicketRegistry实现类指定为上述实现。即修改下面的class值

<!-- Ticket Registry -->
 	<bean id="ticketRegistry" class="org.jasig.cas.util.RedisTicketRegistry" />
	
<!-- 	<bean id="ticketRegistry" class="org.jasig.cas.ticket.registry.DefaultTicketRegistry" />
 -->

因为使用了Redis的expire功能,注释掉如下代码:

<!-- TICKET REGISTRY CLEANER -->
<!-- 	<bean id="ticketRegistryCleaner" class="org.jasig.cas.ticket.registry.support.DefaultTicketRegistryCleaner"
		p:ticketRegistry-ref="ticketRegistry" />
	
	<bean id="jobDetailTicketRegistryCleaner" class="org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean"
		p:targetObject-ref="ticketRegistryCleaner"
		p:targetMethod="clean" />
	
	<bean id="triggerJobDetailTicketRegistryCleaner" class="org.springframework.scheduling.quartz.SimpleTriggerBean"
		p:jobDetail-ref="jobDetailTicketRegistryCleaner"
		p:startDelay="20000"
		p:repeatInterval="5000000" /> -->


通过上述实现TicketRegistry,多台CAS服务器就可以共用同一个TicketRegistry。对于如何共享session,我们可以采用现成的第三方工具tomcat-redis-session-manager直接集成即可。对于前端web服务器(如nginx),做好负载均衡配置,将认证请求分布转发给后面多台CAS,实现负载均衡和容错目的。

 

 

 


 

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