Redis高可用-Cluster

数据库架构之美 2021-03-10

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Redis有三种高可用方案：主从，哨兵（sentinel），集群（cluster）。哨兵和集群模式都是基于redis主从来实现的，普通的redis主从无法实现自动的高可用切换。

哨兵模式是在redis主从节点外围部署哨兵集群，哨兵集群是一类特殊的redis，是基于quorum协议的监控集群，至少需要三个节点，哨兵集群会对redis主从节点状态进行监控，如果设定值个数（一般使用多数派）的哨兵监控到主节点的失败，会协商进行主从切换。一套哨兵集群可以监控多套redis主从，具体配置步骤不再赘述。

集群模式也称为redis cluster，redis cluster是一个多节点分布式缓存，架构与分布式数据库有些类似，redis key的crc16值被hash到16384个slot中，所以每个节点存储一部分redis数据，所有节点组成完整的redis集群。客户端可以对每个redis节点进行读写，但是同一时刻只能操作一个key。

redis集群的优势在于可以快速的实现扩缩容，可以在线的新增和删除节点。另外不同于sentinel模式，redis cluster中所有服务器都可以看做主节点，都可以进行读写，所有服务器的资源得到了利用。在高可用方案，每个redis主节点在另外的服务器上都会有一到多个备份的副本，并且基于多数派实现了主节点失败时的自动切换，可以容纳集群少数节点同时失败。

下面以两台机器为例简单看下redis cluster的搭建步骤

两台机器分别创建redis目录：

[root@db1 ~]# mkdir redis-cluster/7001
[root@db1 ~]# mkdir redis-cluster/7002
[root@db1 ~]# mkdir redis-cluster/7003
[root@db2 ~]# mkdir redis-cluster/7004
[root@db2 ~]# mkdir redis-cluster/7005
[root@db2 ~]# mkdir redis-cluster/7006

将编译好的redis二进制包（编译过程略，默认redis源码包里也有编译好的二进制文件）拷贝到7001目录中，一般我习惯使用的目录结构如下

redis-cluster/

└── 7001

├── bin

├── data

├── etc

└── log

编辑配置文件

vi /redis-cluster/7001/etc/redis.conf
bind 0.0.0.0
port 7001
pidfile /var/run/redis_7001.pid
loglevel notice
logfile "/redis-cluster/7001/log/redis_7001.log"
dir /redis-cluster/7001/data
cluster-config-file /redis-cluster/nodes-7001.conf
daemonize yes
supervised no
appendonly yes
cluster-enabled yes
cluster-node-timeout 5000
save 900 1
save 300 10
save 60 10000
dbfilename dump.rdb
appendfilename "appendonly.aof"
appendfsync everysec

按照一样的步骤拷贝配置其他五个节点，然后启动六个redis节点，可以放在脚本中

[root@db1 ~]# /redis/redis-cluster/7001/bin/redis-server /redis/redis-cluster/7001/etc/redis.conf
[root@db1 ~]# /redis/redis-cluster/7002/bin/redis-server /redis/redis-cluster/7002/etc/redis.conf
[root@db1 ~]# /redis/redis-cluster/7003/bin/redis-server /redis/redis-cluster/7003/etc/redis.conf
[root@db2 ~]# /redis/redis-cluster/7004/bin/redis-server /redis/redis-cluster/7004/etc/redis.conf
[root@db2 ~]# /redis/redis-cluster/7005/bin/redis-server /redis/redis-cluster/7005/etc/redis.conf
[root@db2 ~]# /redis/redis-cluster/7006/bin/redis-server /redis/redis-cluster/7006/etc/redis.conf

执行命令进行集群创建

[root@db1 ~]# redis-cli --cluster create  192.168.1.1:7001 192.168.1.1:7002 192.168.1.1:7003 192.168.1.2:7004 192.168.1.2:7005 192.168.1.2:7006 --cluster-replicas 1
>>> Performing hash slots allocation on 6 nodes...
Master[0] -> Slots 0 - 5460
Master[1] -> Slots 5461 - 10922
Master[2] -> Slots 10923 - 16383
Adding replica 192.168.1.2:7006 to 192.168.1.1:7001
Adding replica 192.168.1.1:7003 to 192.168.1.2:7004
Adding replica 192.168.1.2:7005 to 192.168.1.1:7002
M: 5fca048d05b26211e5ccb8b932b6327d31773822 192.168.1.1:7001
   slots:[0-5460] (5461 slots) master
M: 4f98b53609307f11674b60bd84caecce3ff8d18e 192.168.1.1:7002
   slots:[10923-16383] (5461 slots) master
S: fddf4c97eeb6f59d0de9e45cb0899b309e90d537 192.168.1.1:7003
   replicates 84e20fd036d2b1c37d0071a632b08138490f0173
M: 84e20fd036d2b1c37d0071a632b08138490f0173 192.168.1.2:7004
   slots:[5461-10922] (5462 slots) master
S: 9769e3b34a0bdee505bba06a8dc924928917671b 192.168.1.2:7005
   replicates 4f98b53609307f11674b60bd84caecce3ff8d18e
S: 9c6d002711965fbcbc945fa6ba99ab18b4c04810 192.168.1.2:7006
   replicates 5fca048d05b26211e5ccb8b932b6327d31773822
Can I set the above configuration? (type 'yes' to accept): yes
>>> Nodes configuration updated
>>> Assign a different config epoch to each node
>>> Sending CLUSTER MEET messages to join the cluster
Waiting for the cluster to join
..
>>> Performing Cluster Check (using node 192.168.1.1:7001)
M: 5fca048d05b26211e5ccb8b932b6327d31773822 192.168.1.1:7001
   slots:[0-5460] (5461 slots) master
   1 additional replica(s)
M: 84e20fd036d2b1c37d0071a632b08138490f0173 192.168.1.2:7004
   slots:[5461-10922] (5462 slots) master
   1 additional replica(s)
S: fddf4c97eeb6f59d0de9e45cb0899b309e90d537 192.168.1.1:7003
   slots: (0 slots) slave
   replicates 84e20fd036d2b1c37d0071a632b08138490f0173
S: 9769e3b34a0bdee505bba06a8dc924928917671b 192.168.1.2:7005
   slots: (0 slots) slave
   replicates 4f98b53609307f11674b60bd84caecce3ff8d18e
M: 4f98b53609307f11674b60bd84caecce3ff8d18e 192.168.1.1:7002
   slots:[10923-16383] (5461 slots) master
   1 additional replica(s)
S: 9c6d002711965fbcbc945fa6ba99ab18b4c04810 192.168.1.2:7006
   slots: (0 slots) slave
   replicates 5fca048d05b26211e5ccb8b932b6327d31773822
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

集群相关检查命令

[root@db1 redis-cluster]# redis-cli -p 7001 cluster info
[root@db1 redis-cluster]# redis-cli -p 7001 cluster nodes

redis

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Redis高可用-Cluster

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