springboot项目创建笔记25 之《集成redis集群哈希槽》

1、配置文件中添加

#redis集群配置
spring:
    redis:
        database: 0
        password: 
        cluster:
            #加入所有redis节点
            nodes: 192.168.1.138:6381,192.168.1.138:6382,192.168.1.138:6383,192.168.1.138:6384,192.168.1.138:6385,192.168.1.138:6386
        lettuce:
            pool:
                max-active: 16
                max-idle: 32
                max-wait: -1
                min-idle: 8

redis的集群读写操作，数据都会被切成3份，放在不同的master里面
redis的主从，里面的数据一定是一样的

2、启动应用发现报错

Exception in thread "Thread-10" 2021-07-26 13:20:56.860 [] INFO  [Thread-2] com.example.service.TaskHotProductService :刷新缓存完成
org.springframework.data.redis.RedisSystemException: Error in execution; nested exception is io.lettuce.core.RedisCommandExecutionException: CROSSSLOT Keys in request don't hash to the same slot
	at org.springframework.data.redis.connection.lettuce.LettuceExceptionConverter.convert(LettuceExceptionConverter.java:54)
	at org.springframework.data.redis.connection.lettuce.LettuceExceptionConverter.convert(LettuceExceptionConverter.java:52)
	at org.springframework.data.redis.connection.lettuce.LettuceExceptionConverter.convert(LettuceExceptionConverter.java:41)
	at org.springframework.data.redis.PassThroughExceptionTranslationStrategy.translate(PassThroughExceptionTranslationStrategy.java:44)
	at org.springframework.data.redis.FallbackExceptionTranslationStrategy.translate(FallbackExceptionTranslationStrategy.java:42)
	at org.springframework.data.redis.connection.lettuce.LettuceConnection.convertLettuceAccessException(LettuceConnection.java:268)
	at org.springframework.data.redis.connection.lettuce.LettuceZSetCommands.convertLettuceAccessException(LettuceZSetCommands.java:903)
	at org.springframework.data.redis.connection.lettuce.LettuceZSetCommands.zUnionStore(LettuceZSetCommands.java:624)
	at org.springframework.data.redis.connection.DefaultedRedisConnection.zUnionStore(DefaultedRedisConnection.java:868)
	at org.springframework.data.redis.core.DefaultZSetOperations.lambda$unionAndStore$26(DefaultZSetOperations.java:424)
	at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:224)
	at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:184)
	at org.springframework.data.redis.core.AbstractOperations.execute(AbstractOperations.java:95)
	at org.springframework.data.redis.core.DefaultZSetOperations.unionAndStore(DefaultZSetOperations.java:424)
	at com.example.service.TaskWeiBoDayHourService.refreshDay(TaskWeiBoDayHourService.java:95)
	at com.example.service.TaskWeiBoDayHourService.refreshData(TaskWeiBoDayHourService.java:71)
	at com.example.service.TaskWeiBoDayHourService.lambda$1(TaskWeiBoDayHourService.java:36)
	at java.lang.Thread.run(Thread.java:748)

原因是在执行：

//把当前的时间key，并且把后推23个小时，共计近24个小时，求出并集存入Constants.DAY_KEY中
redisTemplate.opsForZSet().unionAndStore(Constants.HOUR_KEY + hour , otherKeys, Constants.DAY_KEY);

合并各个集合的key时，涉及多key操作，而要执行多key操作，在redis集群里被限制在同一个哈希槽中才能执行

3、解决办法
用HashTag标记，HashTag即是用{}包裹key的一个子串，只有在{}的内容才计算哈希值，这样可以保证落在同一个哈希槽中

	public static final String HOUR_KEY = "{rank}:hour:";
	public static final String DAY_KEY = "{rank}:day";
	public static final String WEEK_KEY = "{rank}:week";
	public static final String MONTH_KEY = "{rank}:month";

参考资料：
https://blog.csdn.net/sinat_29843547/article/details/76508055
https://blog.csdn.net/one312/article/details/105269380

注：最新代码上传至https://github.com/csj50/myboot