Spring整合Redis之集群与故障转移

淩亂°似流年 2022-06-10 00:44 835阅读 0赞

### **前言** ###

本文主要讲解spring整合redis集群，关于redis集群搭建网上相关文章挺多的，大家可以自己先搭建好，可以参考[官网][Link 1]或[中文版官网][Link 2]。本文假设你已经搭建好集群了，笔者redis(版本4.0.1)集群环境如下图：

![正常集群状态][1da6fdba5ae6df5eb76adf20a7197ae1.png]

7000、7001、7002三个主节点，7003、7004、7005三个从节点。Redis集群共有16384个哈希槽（hash slot）用于存放key，当前3个节点哈希槽分布为：

*  节点 7000 包含 0 到 5460号哈希槽
 *  节点 7001 包含 5461 到 10922 号哈希槽
 *  节点 7002 包含 10923 到 16383 号哈希槽

### **spring整合redis cluster** ###

#### **step1、maven依赖引入** ####

<dependencies>
        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-redis</artifactId>
            <version>1.8.6.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>redis.clients</groupId>
            <artifactId>jedis</artifactId>
            <version>2.9.0</version>
        </dependency>
    </dependencies>

#### **step2、配置ConnectionFactory** ####

建立集群连接需要获取RedisClusterConnection实例，该实例通过RedisConnectionFactory获取，可以如下配置

JedisConnectionFactory是RedisConnectionFactory的实现，构造函数需要两个参数，分别是集群配置clusterConfig和池配置poolConfig，下面一一来看

#### **step3、配置JedisPoolConfig** ####

各个属性值从属性文件中读取，需要如下配置

<context:property-placeholder location="classpath:*.properties" ignore-unresolvable="true" />

属性文件spring-redis.properties内容

redis.minIdle=50
    redis.maxIdle=200
    redis.maxActive=100
    redis.maxWait=3000
    redis.testOnBorrow=true

#### **step4、配置RedisClusterConfiguration** ####

集群配置有两种方式

1.clusterNodes设值注入

2.propertySource构造注入

构造函数参数类型为org.springframework.core.env.PropertySource，我们使用它的实现类ResourcePropertySource

spring-redis-cluster.properties内容：

#集群节点host:port,多个节点逗号分隔
    spring.redis.cluster.nodes=192.168.48.28:7000,192.168.48.28:7001,192.168.48.28:7002
    spring.redis.cluster.max-redirects=5

查看RedisClusterConfiguration源码可以看到这两个配置属性常量

![RedisClusterConfiguration源码][RedisClusterConfiguration]

个人比较喜欢第二种配置，更加简洁

#### **step5、配置RedisTemplate** ####

然后配置RedisTemplate，我们用StringRedisTemplate实现

#### **step6、测试** ####

通过main方法测试一下

package example;
    
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    import org.springframework.data.redis.core.StringRedisTemplate;
    import org.springframework.data.redis.core.ValueOperations;
    
    public class SpringMain { 
    
        public static void main(String[] args) throws InterruptedException { 
            ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:spring-redis.xml");
            StringRedisTemplate template = context.getBean(StringRedisTemplate.class);
            ValueOperations<String, String> valueOperations = template.opsForValue();
            valueOperations.set("key1","value1");
            valueOperations.set("key2","value2");
            valueOperations.set("key3","value3");
            valueOperations.set("key4","value4");
            valueOperations.set("key5","value5");
            valueOperations.set("key6","value6");
            System.exit(0);
        }
    }

通过命令行连接redis服务器查看结果：

![测试结果][255029b4cb69e3718cae5ba85c350cc1.png]

每个key通过CRC16（详情参考[官网][Link 3]）校验后对16384取模放到对应哈希槽（hash slot）中。redis-cli客户端工具会根据哈希槽（hash slot）所在节点进行跳转，所以会看到“-> Redirected to slot…”的提示。  
最后贴下完整配置：

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xmlns:redis="http://www.springframework.org/schema/redis" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/redis http://www.springframework.org/schema/redis/spring-redis.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
    
        <context:property-placeholder location="classpath:*.properties" ignore-unresolvable="true" />
    
        
        <bean id="jedisConnectionFactory" class="org.springframework.data.redis.connection.jedis.JedisConnectionFactory">
            <constructor-arg name="clusterConfig" ref="redisClusterConfiguration"/>
            <constructor-arg name="poolConfig" ref="jedisPoolConfig" />
        </bean>
    
        
        <bean id="redisClusterConfiguration" class="org.springframework.data.redis.connection.RedisClusterConfiguration">
            <constructor-arg name="propertySource" ref="propertySource"/>
          
        </bean>
    
        <bean name="propertySource" class="org.springframework.core.io.support.ResourcePropertySource">
            <constructor-arg name="location" value="classpath:spring-redis-cluster.properties" />
        </bean>
    
        
        <bean id="jedisPoolConfig" class="redis.clients.jedis.JedisPoolConfig" >
            <property name="minIdle" value="${redis.minIdle}" />
            <property name="maxIdle" value="${redis.maxIdle}" />
            <property name="maxTotal" value="${redis.maxActive}" />
            <property name="maxWaitMillis" value="${redis.maxWait}" />
            <property name="testOnBorrow" value="${redis.testOnBorrow}" />
            <property name="testOnReturn" value="true" />
            <property name="testWhileIdle" value="true" />
        </bean>
        
        
        <bean id="stringRedisTemplate" class="org.springframework.data.redis.core.StringRedisTemplate" p:connection-factory-ref="jedisConnectionFactory"/>
        
    </beans>

### **redis集群进阶** ###

#### **故障转移** ####

现在我们来测试下故障转移，通过向端口号为7002的主节点发送**DEBUG SEGFAULT**命令， 让这个主节点崩溃：

$ redis-cli -p 7002 debug segfault

查看现在集群节点状态：

![7002fail][]

可以看到7002状态为fail,他的从节点7005被选举为新的主节点  
根据前面的测试我们知道键key4被“hash”到了13120哈希槽，位于7002节点，现在7002挂了，他会放到哪呢？

ValueOperations<String, String> valueOperations = template.opsForValue();
    valueOperations.set("key4","bar4");

![7002fail 后故障转移][7002fail 1]

可以看见，13120哈希槽已经转移到新的主节点7005上了

#### **主从复制模型** ####

如果上步新的主节点7005也挂了会出现什么情况呢？我们让这个节点崩溃：

$ redis-cli -p 7005 debug segfault

![make 7005 fail command][]

查看现在集群节点状态：

![7002 and 7005 both fail][]

可以看到7005的状态也为fail，现在通过spring redis发送命令，会报连接异常

Exception in thread "main" org.springframework.data.redis.RedisConnectionFailureException: Could not get a resource from the pool; nested exception is redis.clients.jedis.exceptions.JedisConnectionException: Could not get a resource from the pool
    	at org.springframework.data.redis.connection.jedis.JedisExceptionConverter.convert(JedisExceptionConverter.java:67)
    	at org.springframework.data.redis.connection.jedis.JedisExceptionConverter.convert(JedisExceptionConverter.java:41)
    	at org.springframework.data.redis.PassThroughExceptionTranslationStrategy.translate(PassThroughExceptionTranslationStrategy.java:37)
    	at org.springframework.data.redis.connection.jedis.JedisClusterConnection.convertJedisAccessException(JedisClusterConnection.java:3999)
    	at org.springframework.data.redis.connection.jedis.JedisClusterConnection.set(JedisClusterConnection.java:642)
    	at org.springframework.data.redis.connection.DefaultStringRedisConnection.set(DefaultStringRedisConnection.java:744)
    	at org.springframework.data.redis.core.DefaultValueOperations$10.inRedis(DefaultValueOperations.java:172)
    	at org.springframework.data.redis.core.AbstractOperations$ValueDeserializingRedisCallback.doInRedis(AbstractOperations.java:57)
    	at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:207)
    	at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:169)
    	at org.springframework.data.redis.core.AbstractOperations.execute(AbstractOperations.java:91)
    	at org.springframework.data.redis.core.DefaultValueOperations.set(DefaultValueOperations.java:169)
    	at example.SpringMain.main(SpringMain.java:26)

再看看通过命令行向集群发送命令：

![cluster down][]

发现整个集群已经宕掉了，根据redis主从复制模型，当某个主节点和他的所有从节点都挂掉，集群会因为缺少某一范围的哈希槽而不用，如上集群7002主节点7005从节点都挂了，集群因缺少10923-16383范围哈希槽而变的不可用。

**参考**

spring-data-redis cluster:https://docs.spring.io/spring-data/redis/docs/2.0.0.RC2/reference/html/\#cluster

中文官网Redis集群教程:http://www.redis.cn/topics/cluster-tutorial.html

[Link 1]: https://redis.io/topics/cluster-tutorial
[Link 2]: http://www.redis.cn/topics/cluster-tutorial.html
[1da6fdba5ae6df5eb76adf20a7197ae1.png]: /images/20220610/caf35458421b493ea2e65e32cf70f012.png
[RedisClusterConfiguration]: /images/20220610/cc90695c931140d2be34b95b65027c25.png
[255029b4cb69e3718cae5ba85c350cc1.png]: /images/20220610/06730c13f05d4955aac531feb668f7e8.png
[Link 3]: http://www.redis.cn/topics/cluster-spec.html
[7002fail]: /images/20220610/71a891838778492e84ebfa9ba418c349.png
[7002fail 1]: /images/20220610/f482b036da83445d9369b5e4d56d6603.png
[make 7005 fail command]: /images/20220610/8afadb21c5c643e084af4f81b9c48deb.png
[7002 and 7005 both fail]: /images/20220610/2e9cc18d0581420eb80a150f811afb31.png
[cluster down]: /images/20220610/14e98b8fd25d4f83b8daf15f895ff016.png