redis 集群总共有三台机器，一主两从，共计启动 9 个实例。 redis 集群机器宕机后，可能会出现两个 master 节点落到一台机器上的情况，若此机器宕机，在其他节点尚未选举出新的主节点之前，集群只有一个主节点，存在单点风险。
redis 集群信息
| IP | 端口 |
|---|---|
| 192.168.100.71 | 7000(主) 7002 7003 |
| 192.168.100.72 | 7000(主) 7001 7003 |
| 192.168.100.73 | 7000(主) 7001 7002 |
初始化并重新创建集群
禁止业务机器往集群写入
由于业务机器上的服务会连接 redis 写入数据，集群初始化会失败，需要禁止写入，可以使用 iptables，只允许集群内的机器访问 7000-70003 端口，拒绝其他机器连接。
iptables -A INPUT -p tcp -s 192.168.100.71 -m multiport --dports 7000:7003 -j ACCEPT
iptables -A INPUT -p tcp -s 192.168.100.72 -m multiport --dports 7000:7003 -j ACCEPT
iptables -A INPUT -p tcp -s 192.168.100.73 -m multiport --dports 7000:7003 -j ACCEPT
iptables -A INPUT -p tcp -m multiport --dports 7000:7003 -j DROP
删除本地备份文件
rm -f /usr/local/redis/cluster/nodes-7000.conf /usr/local/redis/cluster/nodes-7001.conf /usr/local/redis/cluster/nodes-7002.conf /usr/local/redis/cluster/nodes-7003.conf
rm -f /usr/local/redis/cluster/dump.rdb
停止 redis
ps -ef grep -E ‘7000 7001 7002 7003’ grep -v grep awk ‘{print $2}’ xargs kill -9
启动 redis
- 192.168.100.71
/usr/local/redis-cluster/bin/redis-server /usr/local/redis-cluster/cluster/7000/redis7000.conf
/usr/local/redis-cluster/bin/redis-server /usr/local/redis-cluster/cluster/7002/redis7002.conf
/usr/local/redis-cluster/bin/redis-server /usr/local/redis-cluster/cluster/7003/redis7003.conf
- 192.168.100.72
/usr/local/redis-cluster/bin/redis-server /usr/local/redis-cluster/cluster/7000/redis7000.conf
/usr/local/redis-cluster/bin/redis-server /usr/local/redis-cluster/cluster/7001/redis7001.conf
/usr/local/redis-cluster/bin/redis-server /usr/local/redis-cluster/cluster/7003/redis7003.conf
- 192.168.100.73
/usr/local/redis-cluster/bin/redis-server /usr/local/redis-cluster/cluster/7000/redis7000.conf
/usr/local/redis-cluster/bin/redis-server /usr/local/redis-cluster/cluster/7001/redis7001.conf
/usr/local/redis-cluster/bin/redis-server /usr/local/redis-cluster/cluster/7002/redis7002.conf
重置集群
执行 cluster reset 重置，清理旧的集群信息。
- 192.168.100.71
redis-cli -h 192.168.100.71 -p 7000 -c cluster reset
redis-cli -h 192.168.100.71 -p 7002 -c cluster reset
redis-cli -h 192.168.100.71 -p 7003 -c cluster reset
- 192.168.100.72
redis-cli -h 192.168.100.72 -p 7000 -c cluster reset
redis-cli -h 192.168.100.72 -p 7001 -c cluster reset
redis-cli -h 192.168.100.72 -p 7003 -c cluster reset
- 192.168.100.73
redis-cli -h 192.168.100.73 -p 7000 -c cluster reset
redis-cli -h 192.168.100.73 -p 7001 -c cluster reset
redis-cli -h 192.168.100.73 -p 7002 -c cluster reset
清空数据
- 192.168.100.71
redis-cli -h 192.168.100.71 -p 7000 flushdb
redis-cli -h 192.168.100.71 -p 7002 flushdb
redis-cli -h 192.168.100.71 -p 7003 flushdb
- 192.168.100.72
redis-cli -h 192.168.100.72 -p 7000 flushdb
redis-cli -h 192.168.100.72 -p 7001 flushdb
redis-cli -h 192.168.100.72 -p 7003 flushdb
- 192.168.100.73
redis-cli -h 192.168.100.73 -p 7000 flushdb
redis-cli -h 192.168.100.73 -p 7001 flushdb
redis-cli -h 192.168.100.73 -p 7002 flushdb
创建集群
登录第一台机器 192.168.100.71，执行以下命令创建即可。
cd /data/pkg/redis-3.0.4/src
./redis-trib.rb create 192.168.100.71:7000 192.168.100.72:7000 192.168.100.73:7000
>>> Creating cluster
/usr/local/lib/ruby/gems/2.5.0/gems/redis-3.3.0/lib/redis/client.rb:459: warning: constant ::Fixnum is deprecated
>>> Performing hash slots allocation on 3 nodes...
Using 3 masters:
192.168.100.71:7000
192.168.100.72:7000
192.168.100.73:7000
M: c966ac76a40be0c58a8295f0ce4fac800a89ffc0 192.168.100.71:7000
slots:0-5460 (5461 slots) master
M: 8a3b3c98d2d9feb75227b3054da00ed5abb6a 192.168.100.72:7000
slots:5461-10922 (5462 slots) master
M: a6396903ffc958711481836ceff121ddd2ff752d 192.168.100.73:7000
slots:10923-16383 (5461 slots) master
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 192.168.100.71:7000)
M: c966ac76a40be0c58a8295f0ce4fac800a89ffc0 192.168.100.71:7000
slots:0-5460 (5461 slots) master
0 additional replica(s)
M: a6396903ffc958711481836ceff121ddd2ff752d 192.168.100.73:7000
slots:10923-16383 (5461 slots) master
0 additional replica(s)
M: 8a3b3c98d2d9feb75227b3054da00ed5abb6a 192.168.100.72:7000
slots:5461-10922 (5462 slots) master
0 additional replica(s)
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
指定主节点
在第一台机器上继续操作，手动指定三个主节点及其对应的从节点。
./redis-trib.rb add-node --slave --master-id c966ac76a40be0c58a8295f0ce4fac800a89ffc0 192.168.100.72:7001 192.168.100.71:7000
./redis-trib.rb add-node --slave --master-id c966ac76a40be0c58a8295f0ce4fac800a89ffc0 192.168.100.73:7001 192.168.100.71:7000
./redis-trib.rb add-node --slave --master-id 8a3b3c98d2d9feb75227b3054da00ed5abb6a113 192.168.100.71:7002 192.168.100.72:7000
./redis-trib.rb add-node --slave --master-id 8a3b3c98d2d9feb75227b3054da00ed5abb6a113 192.168.100.73:7002 192.168.100.72:7000
./redis-trib.rb add-node --slave --master-id a6396903ffc958711481836ceff121ddd2ff752d 192.168.100.71:7003 192.168.100.73:7000
./redis-trib.rb add-node --slave --master-id a6396903ffc958711481836ceff121ddd2ff752d 192.168.100.72:7003 192.168.100.73:7000
查看集群状态
redis-cli -h 192.168.100.71 -p 7000 cluster info
redis-cli -h 192.168.100.71 -p 7000 cluster nodes
删除新增的防火墙规则
# 显示规则和相对应的编号
iptables -L -n --line-number
# 找到新增规则对应的编号，删除
iptables -D INPUT 规则编号