基于Redis的CAS服务端集群

为了保证生产环境CAS(Central Authentication Service)认证服务的高可用，防止出现单点故障，我们需要对CAS Server进行集群部署。

CAS的Ticket默认是以Map的方式存储在JVM内存中的，多个tomcat之间无法共享，因此我们可以使用MemCached或者Redis来存储Ticket。MemCached的方式官方已经提供了解决方案，我们这里使用的是Redis，具体实现可以参考CAS的模块：cas-server-integration-memcached。

1、pom.xml文件中加入依赖：

<dependency>
  <groupId>redis.clients</groupId>
  <artifactId>jedis</artifactId>
  <version>2.7.2</version>
</dependency>
<dependency>
  <groupId>org.springframework.data</groupId>
  <artifactId>spring-data-redis</artifactId>
  <version>1.6.0.RELEASE</version>
</dependency>

2、参考：org.jasig.cas.ticket.registry.MemCacheTicketRegistry，重写Ticket注册类。

package com.***.cas.ticket.registry;

import org.jasig.cas.ticket.ServiceTicket;
import org.jasig.cas.ticket.Ticket;
import org.jasig.cas.ticket.TicketGrantingTicket;
import org.jasig.cas.ticket.registry.AbstractDistributedTicketRegistry;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.data.redis.core.RedisTemplate;

import javax.validation.constraints.Min;
import javax.validation.constraints.NotNull;
import java.util.Collection;
import java.util.concurrent.TimeUnit;

public final class RedisTicketRegistry extends AbstractDistributedTicketRegistry implements DisposableBean {

    /** Memcached client. */
    @NotNull
    private final RedisTemplate<String, Object> redisTemplate;

    /**
     * TGT cache entry timeout in seconds.
     */
    @Min(0)
    private final int tgtTimeout;

    /**
     * ST cache entry timeout in seconds.
     */
    @Min(0)
    private final int stTimeout;

    public RedisTicketRegistry(RedisTemplate<String, Object> redisTemplate, int tgtTimeout, int stTimeout) {
        this.redisTemplate = redisTemplate;
        this.tgtTimeout = tgtTimeout;
        this.stTimeout = stTimeout;
    }

    @Override
    public void addTicket(Ticket ticket) {
        logger.debug("Adding ticket {}", ticket);
        try {
            this.redisTemplate.opsForValue().set(ticket.getId(),ticket, getTimeout(ticket), TimeUnit.SECONDS);
        } catch (Exception e) {
            logger.error("Failed adding {}", ticket, e);
        }

    }

    @Override
    public Ticket getTicket(String ticketId) {
        try {
            final Ticket t = (Ticket) this.redisTemplate.opsForValue().get(ticketId);
            if (t != null) {
                return getProxiedTicketInstance(t);
            }
        } catch (final Exception e) {
            logger.error("Failed fetching {} ", ticketId, e);
        }
        return null;
    }

    @Override
    public boolean