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

 1 version: '3.1'
 2 services:
 3   master:  
 4     image: redis
 5     container_name: redis-master
 6     ports:
 7       - 6379:6379
 8         
 9   slave1:  
10     image: redis
11     container_name: redis-slave-1
12     ports:
13       - 6380:6379
14     command: redis-server --slaveof redis-master 6379
15           
16   slave2:  
17     image: redis
18     container_name: redis-slave-2
19     ports:
20       - 6381:6379
21     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

 1 version: '3.1'
 2 services:
 3   sentinel1:  
 4     image: redis
 5     container_name: redis-sentinel-1
 6     ports:
 7       - 26379:26379
 8     command: redis-sentinel /usr/local/etc/redis/sentinel.conf
 9     volumes:
10       - ./sentinel1.conf:/usr/local/etc/redis/sentinel.conf
11         
12   sentinel2:  
13     image: redis
14     container_name: redis-sentinel-2
15     ports:
16       - 26380:26379
17     command: redis-sentinel /usr/local/etc/redis/sentinel.conf
18     volumes:
19       - ./sentinel2.conf:/usr/local/etc/redis/sentinel.conf
20         
21   sentinel3:  
22     image: redis
23     container_name: redis-sentinel-3
24     ports:
25       - 26381:26379
26     command: redis-sentinel /usr/local/etc/redis/sentinel.conf
27     volumes:
28       - ./sentinel3.conf:/usr/local/etc/redis/sentinel.conf
29         

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

1 port 26379
2 dir /tmp
3 sentinel monitor mymaster 217.0.0.1 6379 2
4 sentinel down-after-milliseconds rmaster 30000
5 sentinel parallel-syncs mymaster 1
6 sentinel failover-timeout mymaster 180000
7 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）

  1 package com.learn.hello.system.utils;
  2 
  3 import lombok.extern.slf4j.Slf4j;
  4 import org.apache.ibatis.cache.Cache;
  5 import org.springframework.data.redis.core.RedisCallback;
  6 import org.springframework.data.redis.core.RedisTemplate;
  7 import org.springframework.data.redis.core.ValueOperations;
  8 
  9 import java.util.concurrent.TimeUnit;
 10 import java.util.concurrent.locks.ReadWriteLock;
 11 import java.util.concurrent.locks.ReentrantReadWriteLock;
 12 
 13 /**
 14  * @ClassName RedisCache
 15  * @Deccription 通过redis实现mybaits的二级缓存
 16  * @Author DZ
 17  * @Date 2020/1/12 22:41
 18  **/
 19 @Slf4j
 20 public class RedisCache implements Cache {
 21 
 22     private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
 23     private final String id; // cache instance id
 24     private RedisTemplate redisTemplate;
 25 
 26     private static final long EXPIRE_TIME_IN_MINUTES = 30; // redis过期时间
 27 
 28     public RedisCache(String id) {
 29         if (id == null) {
 30             throw new IllegalArgumentException("Cache instances require an ID");
 31         }
 32         this.id = id;
 33     }
 34 
 35     @Override
 36     public String getId() {
 37         return id;
 38     }
 39 
 40     /**
 41      * Put query result to redis
 42      *
 43      * @param key
 44      * @param value
 45      */
 46     @Override
 47     public void putObject(Object key, Object value) {
 48         try {
 49             RedisTemplate redisTemplate = getRedisTemplate();
 50             ValueOperations opsForValue = redisTemplate.opsForValue();
 51             opsForValue.set(key, value, EXPIRE_TIME_IN_MINUTES, TimeUnit.MINUTES);
 52             log.debug("Put query result to redis");
 53         } catch (Throwable t) {
 54             log.error("Redis put failed", t);
 55         }
 56     }
 57 
 58     /**
 59      * Get cached query result from redis
 60      *
 61      * @param key
 62      * @return
 63      */
 64     @Override
 65     public Object getObject(Object key) {
 66         try {
 67             RedisTemplate redisTemplate = getRedisTemplate();
 68             ValueOperations opsForValue = redisTemplate.opsForValue();
 69             log.debug("Get cached query result from redis");
 70             return opsForValue.get(key);
 71         } catch (Throwable t) {
 72             log.error("Redis get failed, fail over to db", t);
 73             return null;
 74         }
 75     }
 76 
 77     /**
 78      * Remove cached query result from redis
 79      *
 80      * @param key
 81      * @return
 82      */
 83     @Override
 84     @SuppressWarnings("unchecked")
 85     public Object removeObject(Object key) {
 86         try {
 87             RedisTemplate redisTemplate = getRedisTemplate();
 88             redisTemplate.delete(key);
 89             log.debug("Remove cached query result from redis");
 90         } catch (Throwable t) {
 91             log.error("Redis remove failed", t);
 92         }
 93         return null;
 94     }
 95 
 96     /**
 97      * Clears this cache instance
 98      */
 99     @Override
100     public void clear() {
101         RedisTemplate redisTemplate = getRedisTemplate();
102         redisTemplate.execute((RedisCallback) connection -> {
103             connection.flushDb();
104             return null;
105         });
106         log.debug("Clear all the cached query result from redis");
107     }
108 
109     /**
110      * This method is not used
111      *
112      * @return
113      */
114     @Override
115     public int getSize() {
116         return 0;
117     }
118 
119     @Override
120     public ReadWriteLock getReadWriteLock() {
121         return readWriteLock;
122     }
123 
124     private RedisTemplate getRedisTemplate() {
125         if (redisTemplate == null) {
126             redisTemplate = SpringContextHolder.getBean("redisTemplate");
127         }
128         return redisTemplate;
129     }
130 }

3.在接口类增加redis缓存注解

@CacheNamespace(implementation = RedisCache.class)

例如：

1 @CacheNamespace(implementation = RedisCache.class)
2 public interface RoleMapper extends MyMapper {
3     List selectByCondition(ModelMap modelMap);
4 
5     Role selectById(int id);
6 
7     List selectAllRole();
8 }

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

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

1 mybatis:
2   mapper-locations: classpath:mapper/*.xml
3   #  此配置的作用：xml中不用写实体类的全路径
4   type-aliases-package: com.learn.hello.modules.entity
5   #  查询的null字段也返回
6   configuration:
7     call-setters-on-nulls: true
8     #    开启二级缓存
9     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