Spring Boot 入門（十）：集成Redis哨兵模式，實現Mybatis二級緩存

本片文章續《Spring Boot 入門（九）：集成Quartz定時任務》。本文主要基於redis實現了mybatis二級緩存。較redis緩存，mybaits自帶緩存存在缺點（自行谷歌）。本文是基於docker安裝redis主從模式。

1.redis安裝

（1）首先安裝redis集群模式，建立redis目錄，並編寫主從模式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）.啟動 docker-compose up -d

（3）.建立sentinel文件，並編寫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
        

從模式需要sentinel的conf文件，我創建了3個容器，所以這里需要3份（sentinel1.conf sentinel2.conf sentinel3.conf），內容是一模一樣

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）.啟動：docker-compose up -d

（5）.驗證redis是否已經成功啟動

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

連接redis：redis-cli -p 26379

如下圖，表示啟動成功

 

也可以通過桌面客戶端查看是否啟動成功，如圖，我使用的RedisDesktopManager客戶端

 

 這里有個問題可以思考：傳統的redis集群，即cluster，也有主從模式，現在為什么大家都選擇sentinel主從模式？

 2.編寫RedisCache工具類

網上一大堆，根據自己需要選擇合適的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 通過redis實現mybaits的二級緩存
 * @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過期時間

    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.在接口類增加redis緩存注解

@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();
}

這里也可以直接在MyMapper父接口中增加注解，這樣，所有的接口就不需要單獨增加這個注解（根據業務需要自行素選擇）。

4.配置application.yml

spring:
  redis:
       # 哨兵模式推薦使用lettuce作為客戶端，棄用jedis
    lettuce:
      # 連接池配置
      pool:
        # 連接池中的最小空閑連接，默認 0
        min-idle: 0
        # 連接池中的最大空閑連接，默認 8
        max-idle: 8
        # 連接池最大阻塞等待時間（使用負值表示沒有限制），默認 -1ms
        max-wait: -1ms
        # 連接池最大連接數（使用負值表示沒有限制），默認 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中不用寫實體類的全路徑
  type-aliases-package: com.learn.hello.modules.entity
  #  查詢的null字段也返回
  configuration:
    call-setters-on-nulls: true
    #    開啟二級緩存
    cache-enabled: true

 

5.效果

當進行CURD操作時，相關的檢索sql語句就會緩存到redis，如圖：

 

 當再次對相關數據進行CRUD時，就會走緩存