背景
关于 Redis 在生产中我们一般情况下都会选择 redis cluster 高可用架构部署，既能保证数据分片并且实现节点的故障自动转移。 基本部署拓扑如下：
创建测试集群
- 这里通过我封装的 pig4cloud/redis-cluster:4.0 镜像，即可构建一个 6 个节点的 redis cluster 测试环境。
docker run --name redis-cluster -d -e CLUSTER_ANNOUNCE_IP=宿主机IP \-p 7000-7005:7000-7005 -p 17000-17005:17000-17005 pig4cloud/redis-cluster:4.0复制代码
- 查看集群节点信息
⋊> ./redis-cli -h 172.17.0.111 -p 7000 -c 16:09:48172.17.0.111:7000> cluster nodes3d882206d40935beef84ff564b538d57369e4fd9 172.17.0.111:7003@17003 slave b8d24150df4a221c1045cd9a0696bd1972912d52 0 1591344590000 4 connectedb8d24150df4a221c1045cd9a0696bd1972912d52 172.17.0.111:7001@17001 master - 0 1591344590513 2 connected 5461-10922c21167a6da7f8af31d2dd612d449cdf92ad2e7e9 172.17.0.111:7005@17005 slave 810baa140db6e008a137708f09d4335f5207ede3 0 1591344591000 6 connected810baa140db6e008a137708f09d4335f5207ede3 172.17.0.111:7000@17000 myself,master - 0 1591344590000 1 connected 0-546005d2f9884d350a50ac9e38f575b57f19e864e74c 172.17.0.111:7004@17004 slave b3cf24a918d96a1949f49a1d7b3a965ff9dc858c 0 1591344590011 5 connectedb3cf24a918d96a1949f49a1d7b3a965ff9dc858c 172.17.0.111:7002@17002 master - 0 1591344591617 3 connected 10923-16383复制代码
应用层接入集群
- 这里使用 spring boot 2.2 演示， 默认的连接池使用 lettuce
spring: redis: cluster: nodes: - 172.17.0.111:7000 - 172.17.0.111:7001 - 172.17.0.111:7002 - 172.17.0.111:7003 - 172.17.0.111:7004 - 172.17.0.111:7005复制代码
- 简单使用 redisTemplate 操作集群
@RestControllerpublic class DemoController { @Autowired private RedisTemplate redisTemplate; @GetMapping("/add") public String redis() { redisTemplate.opsForValue().set("k1", "v1"); return "ok"; }}复制代码
- 调用查看日志
⋊> curl http://localhost:8080/addok⏎复制代码
我们会发现操作 k1 是在 7000 节点进行操作写入
[channel=0x5ff7aa8f, /172.17.0.156:50783 -> /172.17.0.111:7000, epid=0x8] write() writeAndFlush command ClusterCommand [command=AsyncCommand [type=SET, output=StatusOutput [output=null, error='null'], commandType=io.lettuce.core.protocol.Command], redirections=0, maxRedirections=5][channel=0x5ff7aa8f, /172.17.0.156:50783 -> /172.17.0.111:7000, epid=0x8] write() done复制代码
模拟单点故障
- 关闭 7000 节点
./redis-cli -h 172.17.0.111 -p 7000 -c172.17.0.111:7000> SHUTDOWN复制代码
- 查看 redis cluster 集群日志 docker logs -f redis-cluster
我们可以看到此时集群选举完毕，完成故障转移
23:S 05 Jun 08:24:49.387 # Starting a failover election for epoch 7.29:M 05 Jun 08:24:49.388 # Failover auth granted to c21167a6da7f8af31d2dd612d449cdf92ad2e7e9 for epoch 726:M 05 Jun 08:24:49.388 # Failover auth granted to c21167a6da7f8af31d2dd612d449cdf92ad2e7e9 for epoch 723:S 05 Jun 08:24:49.389 # Failover election won: I'm the new master.23:S 05 Jun 08:24:49.389 # configEpoch set to 7 after successful failover23:M 05 Jun 08:24:49.389 # Setting secondary replication ID to 5253748ecf5bd7ab3536058fba8cad62d2d5e825, valid up to offset: 1622. New replication ID is 21d6a0b199a1ba655c0279d9c78f9682477ac9a323:M 05 Jun 08:24:49.389 * Discarding previously cached master state.23:M 05 Jun 08:24:49.390 # Cluster state changed: ok复制代码
- 此时集群状态。7005 从 slave 变更为 master
应用层日志
- 大量输出连接 7000 节点异常
io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: /172.17.0.111:7000Caused by: java.net.ConnectException: Connection refusedio.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: /172.17.0.111:7000Caused by: java.net.ConnectException: Connection refusedio.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: /172.17.0.111:7000Caused by: java.net.ConnectException: Connection refused复制代码
- 再次操作 redisTemplate 会发现卡死，等待结果返回
⋊> curl http://localhost:8080/add复制代码
- 原因分析
此时还是操作 k1, 根据 slot 对应连接到 7000 节点，已经连接不到无限尝试重连的问题。 lettuce 客户端并未和 redis cluster 集群状态同步刷新，把宕机节点移除，完成故障转移。
集群拓扑动态感应
拓扑动态感应即客户端能够根据 redis cluster 集群的变化，动态改变客户端的节点情况，完成故障转移。
我们只需要在 spring boot 2.3.0 版本中 开启此特性即可。
spring: redis: lettuce: cluster: refresh: adaptive: true复制代码
- 其实 lettuce 官方一直有这个功能，但 spring data redis 并未跟进，具体内容可以参考 user-content-refreshing-the-cluster-topology-view 章节
旧版本兼容
我们只需要参考 adaptive 开关打开后做了哪些事情，给自己的项目配置上 topology-view 即可
@Bean public LettuceConnectionFactory redisConnectionFactory(RedisProperties redisProperties) { RedisClusterConfiguration redisClusterConfiguration = new RedisClusterConfiguration(redisProperties.getCluster().getNodes()); // https://github.com/lettuce-io/lettuce-core/wiki/Redis-Cluster#user-content-refreshing-the-cluster-topology-view ClusterTopologyRefreshOptions clusterTopologyRefreshOptions = ClusterTopologyRefreshOptions.builder() .enablePeriodicRefresh() .enableAllAdaptiveRefreshTriggers() .refreshPeriod(Duration.ofSeconds(5)) .build(); ClusterClientOptions clusterClientOptions = ClusterClientOptions.builder() .topologyRefreshOptions(clusterTopologyRefreshOptions).build(); // https://github.com/lettuce-io/lettuce-core/wiki/ReadFrom-Settings LettuceClientConfiguration lettuceClientConfiguration = LettuceClientConfiguration.builder() .readFrom(ReadFrom.REPLICA_PREFERRED) .clientOptions(clusterClientOptions).build(); return new LettuceConnectionFactory(redisClusterConfiguration, lettuceClientConfiguration); }
