Redis - Redis command timed out nested exception is io.lettuce.core.RedisCommandTimeoutException_redis command timed out; nested exception is io.le

报错信息

ERROR org.springframework.dao.QueryTimeoutException: Redis command timed out; nested exception is io.lettuce.core.RedisCommandTimeoutException: Command timed out after 500 millisecond(s)
	at org.springframework.data.redis.connection.lettuce.LettuceExceptionConverter.convert(LettuceExceptionConverter.java:70)
	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.LettuceListCommands.convertLettuceAccessException(LettuceListCommands.java:490)
	at org.springframework.data.redis.connection.lettuce.LettuceListCommands.lLen(LettuceListCommands.java:159)
	at org.springframework.data.redis.connection.DefaultedRedisConnection.lLen(DefaultedRedisConnection.java:465)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	****
Caused by: io.lettuce.core.RedisCommandTimeoutException: Command timed out after 500 millisecond(s)
	at io.lettuce.core.ExceptionFactory.createTimeoutException(ExceptionFactory.java:51)
	at io.lettuce.core.LettuceFutures.awaitOrCancel(LettuceFutures.java:114)
	at io.lettuce.core.FutureSyncInvocationHandler.handleInvocation(FutureSyncInvocationHandler.java:69)
	at io.lettuce.core.internal.AbstractInvocationHandler.invoke(AbstractInvocationHandler.java:80)
	at com.sun.proxy.$Proxy196.llen(Unknown Source)
	at org.springframework.data.redis.connection.lettuce.LettuceListCommands.lLen(LettuceListCommands.java:157)
	... 134 more

原因分析

• 这个情况是我在将SpringBoot从1.X升级到2.X的时候产生的问题，所以大致可以猜到是版本问题。

解决办法

• 设置超时时间（不推荐）

redis:
    port: 6379
    jedis:
      pool:
        max-active: 50
        max-wait: 5000
        max-idle: 50
        min-idle: 0
    timeout: 500
    host: 47.100.21.110

这种方法无效，解决不了这个问题，我从0改到500还是报错。但是网上绝大多数都是这种方式，实际上我刚更改过来的时候有效过一阵，之后就又不行了。

• 更改依赖（亲测有效）

<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

在SpringBoot 1.X版本的jar包依赖中，点击进去依赖项如下：

<dependencies>
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter</artifactId>
	</dependency>
	<dependency>
		<groupId>org.springframework.data</groupId>
		<artifactId>spring-data-redis</artifactId>
	</dependency>
	<dependency>
		<groupId>redis.clients</groupId>
		<artifactId>jedis</artifactId>
	</dependency>
</dependencies>

升级到SpringBoot 2.X版本之后依赖如下：

<dependencies>
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter</artifactId>
		<version>2.1.2.RELEASE</version>
		<scope>compile</scope>
	</dependency>
	<dependency>
		<groupId>org.springframework.data</groupId>
		<artifactId>spring-data-redis</artifactId>
		<version>2.1.4.RELEASE</version>
		<scope>compile</scope>
		<exclusions>
			<exclusion>
				<artifactId>jcl-over-slf4j</artifactId>
				<groupId>org.slf4j</groupId>
			</exclusion>
		</exclusions>
	</dependency>
	<dependency>
		<groupId>io.lettuce</groupId>
		<artifactId>lettuce-core</artifactId>
		<version>5.1.3.RELEASE</version>
		<scope>compile</scope>
	</dependency>
</dependencies>

可以看到变化是从jedis依赖变成了lettuce-core依赖，而上面的报错io.lettuce.core.RedisCommandTimeoutException也是lettuce-core的异常，所以我的解决方式是先将依赖换回jedis：

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-data-redis</artifactId>
	<exclusions>
		<exclusion>
			<groupId>io.lettuce</groupId>
			<artifactId>lettuce-core</artifactId>
		</exclusion>
	</exclusions>
</dependency>
<dependency>
	<groupId>redis.clients</groupId>
	<artifactId>jedis</artifactId>
</dependency>

如上，配置文件不变，Redis连接成功，不再报错。