redis key过期事件实现过期提醒

比眉伴天荒 2022-05-10 11:40 443阅读 0赞

**redis默认关闭，不建议开启。本文提供参考。键空间通知通常是不启用的，因为这个过程会产生额外消耗。**

# 1、开启redis配置 #

#
    #  notify-keyspace-events Ex
    #
    #  By default all notifications are disabled because most users don't need
    #  this feature and the feature has some overhead. Note that if you don't
    #  specify at least one of K or E, no events will be delivered.
    notify-keyspace-events "Ex"

<table> 
 <tbody> 
 <tr> 
 <th>字符</th> 
 <th>发送通知</th> 
 </tr> 
 </tbody> 
 <tbody> 
 <tr> 
 <td>K</td> 
 <td>键空间通知，所有通知以&nbsp;keyspace@&nbsp;为前缀，针对Key</td> 
 </tr> 
 <tr> 
 <td>E</td> 
 <td>键事件通知，所有通知以&nbsp;keyevent@&nbsp;为前缀，针对event</td> 
 </tr> 
 <tr> 
 <td>g</td> 
 <td>DEL 、 EXPIRE 、 RENAME 等类型无关的通用命令的通知</td> 
 </tr> 
 <tr> 
 <td>$</td> 
 <td>字符串命令的通知</td> 
 </tr> 
 <tr> 
 <td>l</td> 
 <td>列表命令的通知</td> 
 </tr> 
 <tr> 
 <td>s</td> 
 <td>集合命令的通知</td> 
 </tr> 
 <tr> 
 <td>h</td> 
 <td>哈希命令的通知</td> 
 </tr> 
 <tr> 
 <td>z</td> 
 <td>有序集合命令的通知</td> 
 </tr> 
 <tr> 
 <td>x</td> 
 <td>过期事件：每当有过期键被删除时发送</td> 
 </tr> 
 <tr> 
 <td>e</td> 
 <td>驱逐(evict)事件：每当有键因为 maxmemory 政策而被删除时发送</td> 
 </tr> 
 <tr> 
 <td>A</td> 
 <td>参数 g$lshzxe 的别名，相当于是All</td> 
 </tr> 
 </tbody> 
</table>

输入的参数中至少要有一个 K 或者 E ， 否则的话， 不管其余的参数是什么， 都不会有任何通知被分发。上表中斜体的部分为通用的操作或者事件，而黑体则表示特定数据类型的操作。例如，“Kx”表示想监控某个Key的失效事件。

# 2、java实现 #

# 2.1 pom配置 #

spring boot2的配置

<dependencies>
 	
 	<dependency>
 		<groupId>org.springframework.boot</groupId>
 		<artifactId>spring-boot-starter-web</artifactId>
 	</dependency>
 	
 	<dependency>
 		<groupId>org.springframework.boot</groupId>
 		<artifactId>spring-boot-starter-data-redis</artifactId>
 	</dependency>
 	
 	<dependency>
 		<groupId>org.apache.commons</groupId>
 		<artifactId>commons-pool2</artifactId>
 	</dependency>
 </dependencies>

## 2.2 配置 ##

/**
     * @Title: ChannelConstant.java
     * @Package com.spring.pro.constant
     * @Description:
     * @author ybwei
     * @date 2018年8月13日 下午2:12:10
     * @version V1.0
     */
    public interface ChannelConstant {
    
    	/**
    	 * 普通channel
    	 */
    	public final static String channel = "pinpoint.collector.channel";
    
    	
        /**
    	 * 失效key
    	 * __keyevent@0__:expired
    	 * __keyevent必须以此开头；
    	 * @0 表示监听第0个数据库；
    	 * :expired 表示过期事件
    	 */
    	public final static String expired = "__keyevent@0__:expired";
    }

import java.lang.reflect.Method;
 
 import javax.annotation.Resource;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.cache.CacheManager;
 import org.springframework.cache.annotation.CachingConfigurerSupport;
 import org.springframework.cache.annotation.EnableCaching;
 import org.springframework.cache.interceptor.KeyGenerator;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.data.redis.cache.RedisCacheManager;
 import org.springframework.data.redis.connection.RedisConnectionFactory;
 import org.springframework.data.redis.core.RedisTemplate;
 import org.springframework.data.redis.core.StringRedisTemplate;
 import org.springframework.data.redis.listener.ChannelTopic;
 import org.springframework.data.redis.listener.RedisMessageListenerContainer;
 import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;
 
 import com.fasterxml.jackson.annotation.JsonAutoDetect;
 import com.fasterxml.jackson.annotation.PropertyAccessor;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.spring.pro.constant.ChannelConstant;
 import com.spring.pro.listener.KeyExpiredListener;
 import com.spring.pro.listener.UserMsgListener;
 
 /**
 * 缓存管理（注解用）
 * @ClassName: CacheService
 * @Description:
 * @author ybw
 * @date 2017年4月20日 下午5:44:52
 */
 @Configuration
 @EnableCaching // 启动缓存
 public class CacheConfig extends CachingConfigurerSupport {
 
 	/**
 	 * 生成key的策略
 	 * @return
 	 */
 	@Bean
 	public KeyGenerator keyGenerator() {
 		return new KeyGenerator() {
 			@Override
 			public Object generate(Object target, Method method, Object... params) {
 				StringBuilder sb = new StringBuilder();
 				sb.append(target.getClass().getName());
 				sb.append(method.getName());
 				for (Object obj : params) {
 					sb.append(obj.toString());
 				}
 				return sb.toString();
 			}
 		};
 	}
 
 	/**
 	 * 管理缓存
 	 * @param redisTemplate
 	 * @return
 	 */
 	@Bean
 	public CacheManager cacheManager(RedisConnectionFactory redisConnectionFactory) {
 		RedisCacheManager.RedisCacheManagerBuilder builder = RedisCacheManager.RedisCacheManagerBuilder
 				.fromConnectionFactory(redisConnectionFactory);
 		return builder.build();
 	}
 
 	/**
 	 * RedisTemplate配置
 	 * @param factory
 	 * @return
 	 */
 	@Bean
 	public RedisTemplate<String, String> redisTemplate(RedisConnectionFactory factory) {
 		StringRedisTemplate template = new StringRedisTemplate(factory);
 		// 使用Jackson库将对象序列化为JSON字符串
 		Jackson2JsonRedisSerializer<Object> jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer<Object>(
 				Object.class);
 		ObjectMapper om = new ObjectMapper();
 		om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
 		om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
 		jackson2JsonRedisSerializer.setObjectMapper(om);
 		template.setValueSerializer(jackson2JsonRedisSerializer);
 		template.afterPropertiesSet();
 		return template;
 	}
 
 	// --------------------------pub/sub-----------------------------------------
 	@Resource
 	private KeyExpiredListener keyExpiredListener;
 
 		
 	@Bean
 	public ChannelTopic expiredTopic() {
 		return new ChannelTopic(ChannelConstant.expired);
 	}
 
 	@Bean
 	public RedisMessageListenerContainer redisMessageListenerContainer(
 			@Autowired RedisConnectionFactory redisConnectionFactory) {
 		RedisMessageListenerContainer redisMessageListenerContainer = new RedisMessageListenerContainer();
 		redisMessageListenerContainer.setConnectionFactory(redisConnectionFactory);
 		redisMessageListenerContainer.addMessageListener(keyExpiredListener, expiredTopic());
 		return redisMessageListenerContainer;
 	}
 	// --------------------------pub/sub end------------------------------------------
 }

# 3、监听 #

import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.data.redis.connection.Message;
 import org.springframework.data.redis.connection.MessageListener;
 import org.springframework.data.redis.core.RedisTemplate;
 import org.springframework.stereotype.Component;
 
 /**
 * @Title: KeyExpiredListener.java
 * @Package com.spring.pro.listener
 * @Description:
 * @author ybwei
 * @date 2018年8月13日 下午3:54:41
 * @version V1.0
 */
 @Component
 public class KeyExpiredListener implements MessageListener {
 
 	private final static Logger LOG = LoggerFactory.getLogger(UserMsgListener.class);
 	@Autowired
 	private RedisTemplate<?, ?> redisTemplate;
 
 	@Override
 	public void onMessage(Message message, byte[] pattern) {
 		System.out.println("onPMessage pattern " + pattern + " " + " " + message);
 		String channel = new String(message.getChannel());
 		String str = (String) redisTemplate.getValueSerializer().deserialize(message.getBody());
 		LOG.info("received message channel {}, body is {}.", channel, str);
 	}
 
 }

## 4、测试 ##

set aa bb
    expire aa 2 #设置失效时间2秒

aa失效后，即可得到通知。

# 5、注意 #

只会监听过期key，删除key不会监听。