java redis 剩余时间 java中redis定时清空缓存

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mob64ca1409970a 2023-08-30 08:53:14

文章标签 java redis 剩余时间 Redis redis spring 内存不足 文章分类 Java 后端开发

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

序号	策略	描述
1	noeviction	当内存不足以存储新数据写入时,新写入操作报错
2	allkeys-lru	当内存不足以存储新数据写入时,在键空间中移除最近最少使用的key
3	allkeys-random	当内存不足以存储新数据写入时,在键空间中随机移除某个key
4	volatile-lru	当内存不足以存储新数据写入时,在设置了过期时间的键中,移除最近最少使用的key
5	volatile-random	当内存不足以存储新数据写入时,在设置了过期时间的键中,随机移除某个key
6	volatile-ttl	当内存不足以存储新数据写入时,在设置了过期时间的键中,优先移除有更早过期时间的key

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();
            }
        };
    }

   
    @Bean
    public 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();
        // TODO
        logger.info("data expired:{}", expiredKey);
    }
}

4 小结

序号	描述
1	Redis过期清除策略有三种,定期清除,定时清除,惰性清除,其中惰性清除为被动清除,定时和定期为主动清除,定期为定期随机清除,定时为清除所有过期数据
2	数据过期事件提醒配置Redis提醒,设定监听容器及监听事件,监听事件中执行清除数据时的逻辑,同时可获取删除的key,通过key和持久化的数据库同步数据
3	缓存过期数据和硬盘数据同步存储,过期时同步删除,保证服务宕机数据不丢失