Spring Boot 入门（十）：集成Redis哨兵模式，实现Mybatis二级缓存

本片文章续《Spring Boot 入门（九）：集成Quartz定时任务》。本文主要基于redis实现了mybatis二级缓存。较redis缓存，mybaits自带缓存存在缺点（自行谷歌）。本文是基于docker安装redis主从模式。

1.redis安装

（1）首先安装redis集群模式，建立redis目录，并编写主从模式docker-compose.yml文件

version: '3.1'
services:
  master:  
    image: redis
    container_name: redis-master
    ports:
      - 6379:6379
        
  slave1:  
    image: redis
    container_name: redis-slave-1
    ports:
      - 6380:6379
    command: redis-server --slaveof redis-master 6379
          
  slave2:  
    image: redis
    container_name: redis-slave-2
    ports:
      - 6381:6379
    command: redis-server --slaveof redis-master 6379

（2）.启动 docker-compose up -d

（3）.建立sentinel文件，并编写docker-compose.yml文件

version: '3.1'
services:
  sentinel1:  
    image: redis
    container_name: redis-sentinel-1
    ports:
      - 26379:26379
    command: redis-sentinel /usr/local/etc/redis/sentinel.conf
    volumes:
      - ./sentinel1.conf:/usr/local/etc/redis/sentinel.conf
        
  sentinel2:  
    image: redis
    container_name: redis-sentinel-2
    ports:
      - 26380:26379
    command: redis-sentinel /usr/local/etc/redis/sentinel.conf
    volumes:
      - ./sentinel2.conf:/usr/local/etc/redis/sentinel.conf
        
  sentinel3:  
    image: redis
    container_name: redis-sentinel-3
    ports:
      - 26381:26379
    command: redis-sentinel /usr/local/etc/redis/sentinel.conf
    volumes:
      - ./sentinel3.conf:/usr/local/etc/redis/sentinel.conf
        

从模式需要sentinel的conf文件，我创建了3个容器，所以这里需要3份（sentinel1.conf sentinel2.conf sentinel3.conf），内容是一模一样

port 26379
dir /tmp
sentinel monitor mymaster 217.0.0.1 6379 2
sentinel down-after-milliseconds rmaster 30000
sentinel parallel-syncs mymaster 1
sentinel failover-timeout mymaster 180000
sentinel deny-scripts-reconfig yes

（4）.启动：docker-compose up -d

（5）.验证redis是否已经成功启动

进入容器：docker exec -it redis-sentinel-1 /bin/bash

连接redis：redis-cli -p 26379

如下图，表示启动成功

也可以通过桌面客户端查看是否启动成功，如图，我使用的RedisDesktopManager客户端

 

 这里有个问题可以思考：传统的redis集群，即cluster，也有主从模式，现在为什么大家都选择sentinel主从模式？

 2.编写RedisCache工具类

网上一大堆，根据自己需要选择合适的utils（有的utils中方法很全）

package com.learn.hello.system.utils;

import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.cache.Cache;
import org.springframework.data.redis.core.RedisCallback;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.ValueOperations;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * @ClassName RedisCache
 * @Deccription 通过redis实现mybaits的二级缓存
 * @Author DZ
 * @Date 2020/1/12 22:41
 **/
@Slf4j
public class RedisCache implements Cache {

    private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
    private final String id; // cache instance id
    private RedisTemplate redisTemplate;

    private static final long EXPIRE_TIME_IN_MINUTES = 30; // redis过期时间

    public RedisCache(String id) {
        if (id == null) {
            throw new IllegalArgumentException("Cache instances require an ID");
        }
        this.id = id;
    }

    @Override
    public String getId() {
        return id;
    }

    /**
     * Put query result to redis
     *
     * @param key
     * @param value
     */
    @Override
    public void putObject(Object key, Object value) {
        try {
            RedisTemplate redisTemplate = getRedisTemplate();
            ValueOperations opsForValue = redisTemplate.opsForValue();
            opsForValue.set(key, value, EXPIRE_TIME_IN_MINUTES, TimeUnit.MINUTES);
            log.debug("Put query result to redis");
        } catch (Throwable t) {
            log.error("Redis put failed", t);
        }
    }

    /**
     * Get cached query result from redis
     *
     * @param key
     * @return
     */
    @Override
    public Object getObject(Object key) {
        try {
            RedisTemplate redisTemplate = getRedisTemplate();
            ValueOperations opsForValue = redisTemplate.opsForValue();
            log.debug("Get cached query result from redis");
            return opsForValue.get(key);
        } catch (Throwable t) {
            log.error("Redis get failed, fail over to db", t);
            return null;
        }
    }

    /**
     * Remove cached query result from redis
     *
     * @param key
     * @return
     */
    @Override
    @SuppressWarnings("unchecked")
    public Object removeObject(Object key) {
        try {
            RedisTemplate redisTemplate = getRedisTemplate();
            redisTemplate.delete(key);
            log.debug("Remove cached query result from redis");
        } catch (Throwable t) {
            log.error("Redis remove failed", t);
        }
        return null;
    }

    /**
     * Clears this cache instance
     */
    @Override
    public void clear() {
        RedisTemplate redisTemplate = getRedisTemplate();
        redisTemplate.execute((RedisCallback) connection -> {
            connection.flushDb();
            return null;
        });
        log.debug("Clear all the cached query result from redis");
    }

    /**
     * This method is not used
     *
     * @return
     */
    @Override
    public int getSize() {
        return 0;
    }

    @Override
    public ReadWriteLock getReadWriteLock() {
        return readWriteLock;
    }

    private RedisTemplate getRedisTemplate() {
        if (redisTemplate == null) {
            redisTemplate = SpringContextHolder.getBean("redisTemplate");
        }
        return redisTemplate;
    }
}

3.在接口类增加redis缓存注解

@CacheNamespace(implementation = RedisCache.class)

例如：

@CacheNamespace(implementation = RedisCache.class)
public interface RoleMapper extends MyMapper<Role> {
    List<Role> selectByCondition(ModelMap modelMap);

    Role selectById(int id);

    List<Role> selectAllRole();
}

这里也可以直接在MyMapper父接口中增加注解，这样，所有的接口就不需要单独增加这个注解（根据业务需要自行素选择）。

4.配置application.yml

spring:
  redis:
       # 哨兵模式推荐使用lettuce作为客户端，弃用jedis
    lettuce:
      # 连接池配置
      pool:
        # 连接池中的最小空闲连接，默认 0
        min-idle: 0
        # 连接池中的最大空闲连接，默认 8
        max-idle: 8
        # 连接池最大阻塞等待时间（使用负值表示没有限制），默认 -1ms
        max-wait: -1ms
        # 连接池最大连接数（使用负值表示没有限制），默认 8
        max-active: 8
    #    集群模式
    #    cluster:
    #      nodes: 192.168.1.12:6379,192.168.1.12:6380,192.168.1.12:6381
    #    哨兵模式
    sentinel:
      master: mymaster
      nodes: 192.168.1.12:26379,192.168.1.12:26380,192.168.1.12:26381

mybatis:
  mapper-locations: classpath:mapper/*.xml
  #  此配置的作用：xml中不用写实体类的全路径
  type-aliases-package: com.learn.hello.modules.entity
  #  查询的null字段也返回
  configuration:
    call-setters-on-nulls: true
    #    开启二级缓存
    cache-enabled: true

5.效果

当进行CURD操作时，相关的检索sql语句就会缓存到redis，如图：

 当再次对相关数据进行CRUD时，就会走缓存