1 过期策略

1.0 定期删除

• 主动删除
• 定期删除设置一个时间间隔,每个时间段都会检测是否有键过期,定期随机抽取键检查和删除.

1.2 惰性删除

• 被动删除
• 惰性删除不会在键过期是立即删除,而是当外部获取这个键时删除.

1.3 定时删除

• 主动删除
• 创建键时设置过期时间,创建一个定时器,当键达到过期时间阈值时,立即删除键,删除该时刻过期的所有键,不会考虑此时机器所处状态.

2 内存淘汰

3 数据过期提醒

3.1 配置过期提醒

sudo vim /etc/redis/redis.conf

notify-keyspace-events Ex

3.2 配置监听

package com.sb.config;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.cache.RedisCacheConfiguration;
import org.springframework.data.redis.cache.RedisCacheManager;
import org.springframework.data.redis.cache.RedisCacheWriter;
import org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.listener.RedisMessageListenerContainer;
import org.springframework.data.redis.serializer.GenericJackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.CachingConfigurerSupport;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.cache.interceptor.KeyGenerator;import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.ObjectMapper;import java.io.Serializable;
import java.time.Duration;
import java.lang.reflect.Method;@Configuration 
@EnableCaching
@AutoConfigureAfter(RedisAutoConfiguration.class)
public class RedisConfig extends CachingConfigurerSupport{@Autowired private RedisConnectionFactory redisConnectionFactory;@Bean public KeyGenerator wiselyKeyGenerator(){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();}};}@Beanpublic CacheManager cacheManager(RedisConnectionFactory redisConnectionFactory){RedisCacheConfiguration redisCacheConfiguration = RedisCacheConfiguration.defaultCacheConfig().entryTtl(Duration.ofSeconds(60));return RedisCacheManager.builder(RedisCacheWriter.nonLockingRedisCacheWriter(redisConnectionFactory)).cacheDefaults(redisCacheConfiguration).build();}@Bean public RedisTemplate<String, Serializable> redisCacheTemplate(LettuceConnectionFactory redisConnectionFactory){RedisTemplate<String, Serializable> template = new RedisTemplate<>();template.setKeySerializer(new StringRedisSerializer());template.setValueSerializer(new GenericJackson2JsonRedisSerializer());template.setConnectionFactory(redisConnectionFactory);return template;}@Bean public RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory){RedisMessageListenerContainer container = new RedisMessageListenerContainer();container.setConnectionFactory(connectionFactory);return container;}
}

3.3 配置事件处理

package com.sb.util;import org.springframework.data.redis.connection.Message;
import org.springframework.data.redis.listener.KeyExpirationEventMessageListener;
import org.springframework.data.redis.listener.RedisMessageListenerContainer;
import org.springframework.stereotype.Component;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;@Component 
public class RedisKeyExpirationListenerUtil extends KeyExpirationEventMessageListener{static Logger logger = LoggerFactory.getLogger(RedisKeyExpirationListenerUtil.class);public RedisKeyExpirationListenerUtil(RedisMessageListenerContainer listenerContainer){super(listenerContainer);}@Override public void onMessage(Message message, byte[] pattern){String expiredKey = message.toString();// TODOlogger.info("data expired:{}", expiredKey);}
}

4 小结

【参考文献】
[1]https://www.cnblogs.com/mengchunchen/p/10039467.html
[2]https://blog.csdn.net/qq_35981283/article/details/70156422
[3]https://www.jianshu.com/p/c37ad337146f
[4]https://www.jianshu.com/p/106f0eae07c8
[5]https://blog.csdn.net/m0_37367413/article/details/84320562