Redis Cluster扩、缩容

1、Redis Cluster扩容（Redis 5为例）
	因公司业务发展迅猛，现有的三主三从的redis cluster架构可能无法满足现有业务的并发写入需求，因此公司紧急采购两台服务器10.0.0.68，10.0.0.78，需要将其动态添加到集群当中，但不能影响业务使用和数据丢失。
	注意: 生产环境一般建议master节点为奇数个,比如:3,5,7,以防止脑裂现象
1.1、#添加两个节点，增加Redis node节点，需要与之前的Redis node版本相同、配置一致，然后分别再启动两台Redis node，应为一主一从。

#配置node7节点
[root@redis-node7 ~]#dnf -y install redis
[root@redis-node7 ~]#sed -i.bak -e 's/bind 127.0.0.1/bind 0.0.0.0/' -e 
'/masterauth/a masterauth 123456' -e '/# requirepass/a requirepass 123456' -e 
'/# cluster-enabled yes/a cluster-enabled yes' -e '/# cluster-config-file nodes-
6379.conf/a cluster-config-file nodes-6379.conf' -e '/cluster-require-fullcoverage yes/c cluster-require-full-coverage no' /etc/redis.conf
[root@redis-node7 ~]#systemctl enable --now redis
#配置node8节点
[root@redis-node8 ~]#dnf -y install redis
[root@redis-node8 ~]#sed -i.bak -e 's/bind 127.0.0.1/bind 0.0.0.0/' -e 
'/masterauth/a masterauth 123456' -e '/# requirepass/a requirepass 123456' -e 
'/# cluster-enabled yes/a cluster-enabled yes' -e '/# cluster-config-file nodes-
6379.conf/a cluster-config-file nodes-6379.conf' -e '/cluster-require-fullcoverage yes/c cluster-require-full-coverage no' /etc/redis.conf
[root@redis-node8 ~]#systemctl enable --now redis

1.2、 #添加新的master节点到集群
#将一台新的主机10.0.0.68加入集群,以下示例中10.0.0.58可以是任意存在的集群节点
[root@redis-node1 ~]#redis-cli -a 123456 --cluster add-node 10.0.0.68:6379 <当前
任意集群节点>:6379
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
>>> Adding node 10.0.0.68:6379 to cluster 10.0.0.58:6379
>>> Performing Cluster Check (using node 10.0.0.58:6379)
S: 9875b50925b4e4f29598e6072e5937f90df9fc71 10.0.0.58:6379
   slots: (0 slots) slave
   replicates d34da8666a6f587283a1c2fca5d13691407f9462
M: d04e524daec4d8e22bdada7f21a9487c2d3e1057 10.0.0.48:6379
   slots:[5461-10922] (5462 slots) master
   1 additional replica(s)
M: d34da8666a6f587283a1c2fca5d13691407f9462 10.0.0.28:6379
   slots:[10923-16383] (5461 slots) master
   1 additional replica(s)
S: 99720241248ff0e4c6fa65c2385e92468b3b5993 10.0.0.18:6379
   slots: (0 slots) slave
   replicates d04e524daec4d8e22bdada7f21a9487c2d3e1057
S: f9adcfb8f5a037b257af35fa548a26ffbadc852d 10.0.0.38:6379
   slots: (0 slots) slave
   replicates cb028b83f9dc463d732f6e76ca6bbcd469d948a7
M: cb028b83f9dc463d732f6e76ca6bbcd469d948a7 10.0.0.8:6379
   slots:[0-5460] (5461 slots) master
   1 additional replica(s)
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
>>> Send CLUSTER MEET to node 10.0.0.68:6379 to make it join the cluster.
[OK] New node added correctly.
#观察到该节点已经加入成功，但此节点上没有slot位,也无从节点，而且新的节点是master

[root@redis-node1 ~]#redis-cli -a 123456 --cluster info 10.0.0.8:6379
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
10.0.0.8:6379 (cb028b83...) -> 6672 keys | 5461 slots | 1 slaves.
10.0.0.68:6379 (d6e2eca6...) -> 0 keys | 0 slots | 0 slaves.
10.0.0.48:6379 (d04e524d...) -> 6679 keys | 5462 slots | 1 slaves.
10.0.0.28:6379 (d34da866...) -> 6649 keys | 5461 slots | 1 slaves.
[OK] 20000 keys in 5 masters.
1.22 keys per slot on average.
[root@redis-node1 ~]#redis-cli -a 123456 --cluster check 10.0.0.8:6379
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
10.0.0.8:6379 (cb028b83...) -> 6672 keys | 5461 slots | 1 slaves.
10.0.0.68:6379 (d6e2eca6...) -> 0 keys | 0 slots | 0 slaves.
10.0.0.48:6379 (d04e524d...) -> 6679 keys | 5462 slots | 1 slaves.
10.0.0.28:6379 (d34da866...) -> 6649 keys | 5461 slots | 1 slaves.
[OK] 20000 keys in 5 masters.
1.22 keys per slot on average.
>>> Performing Cluster Check (using node 10.0.0.8:6379)
M: cb028b83f9dc463d732f6e76ca6bbcd469d948a7 10.0.0.8:6379
   slots:[0-5460] (5461 slots) master
   1 additional replica(s)
M: d6e2eca6b338b717923f64866bd31d42e52edc98 10.0.0.68:6379
   slots: (0 slots) master
S: 9875b50925b4e4f29598e6072e5937f90df9fc71 10.0.0.58:6379
   slots: (0 slots) slave
   replicates d34da8666a6f587283a1c2fca5d13691407f9462
S: f9adcfb8f5a037b257af35fa548a26ffbadc852d 10.0.0.38:6379
   slots: (0 slots) slave
   replicates cb028b83f9dc463d732f6e76ca6bbcd469d948a7
M: d04e524daec4d8e22bdada7f21a9487c2d3e1057 10.0.0.48:6379
   slots:[5461-10922] (5462 slots) master
   1 additional replica(s)
S: 99720241248ff0e4c6fa65c2385e92468b3b5993 10.0.0.18:6379
   slots: (0 slots) slave
   replicates d04e524daec4d8e22bdada7f21a9487c2d3e1057
M: d34da8666a6f587283a1c2fca5d13691407f9462 10.0.0.28:6379
   slots:[10923-16383] (5461 slots) master
   1 additional replica(s)
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

[root@redis-node1 ~]#cat /var/lib/redis/nodes-6379.conf 
d6e2eca6b338b717923f64866bd31d42e52edc98 10.0.0.68:6379@16379 master - 0
1582356107260 8 connected
9875b50925b4e4f29598e6072e5937f90df9fc71 10.0.0.58:6379@16379 slave 
d34da8666a6f587283a1c2fca5d13691407f9462 0 1582356110286 6 connected
f9adcfb8f5a037b257af35fa548a26ffbadc852d 10.0.0.38:6379@16379 slave 
cb028b83f9dc463d732f6e76ca6bbcd469d948a7 0 1582356108268 4 connected
d04e524daec4d8e22bdada7f21a9487c2d3e1057 10.0.0.48:6379@16379 master - 0
1582356105000 7 connected 5461-10922
99720241248ff0e4c6fa65c2385e92468b3b5993 10.0.0.18:6379@16379 slave 
d04e524daec4d8e22bdada7f21a9487c2d3e1057 0 1582356108000 7 connected
d34da8666a6f587283a1c2fca5d13691407f9462 10.0.0.28:6379@16379 master - 0
1582356107000 3 connected 10923-16383
cb028b83f9dc463d732f6e76ca6bbcd469d948a7 10.0.0.8:6379@16379 myself,master - 0
1582356106000 1 connected 0-5460
vars currentEpoch 8 lastVoteEpoch 7 #和上面显示结果一样

[root@redis-node1 ~]#redis-cli -a 123456 CLUSTER NODES
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
d6e2eca6b338b717923f64866bd31d42e52edc98 10.0.0.68:6379@16379 master - 0
1582356313200 8 connected
9875b50925b4e4f29598e6072e5937f90df9fc71 10.0.0.58:6379@16379 slave 
d34da8666a6f587283a1c2fca5d13691407f9462 0 1582356311000 6 connected
f9adcfb8f5a037b257af35fa548a26ffbadc852d 10.0.0.38:6379@16379 slave 
cb028b83f9dc463d732f6e76ca6bbcd469d948a7 0 1582356314208 4 connected
d04e524daec4d8e22bdada7f21a9487c2d3e1057 10.0.0.48:6379@16379 master - 0
1582356311182 7 connected 5461-10922
99720241248ff0e4c6fa65c2385e92468b3b5993 10.0.0.18:6379@16379 slave 
d04e524daec4d8e22bdada7f21a9487c2d3e1057 0 1582356312000 7 connected
d34da8666a6f587283a1c2fca5d13691407f9462 10.0.0.28:6379@16379 master - 0
1582356312190 3 connected 10923-16383
cb028b83f9dc463d732f6e76ca6bbcd469d948a7 10.0.0.8:6379@16379 myself,master - 0
1582356310000 1 connected 0-5460

#查看集群状态
[root@redis-node1 ~]#redis-cli -a 123456 CLUSTER INFO
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
cluster_state:ok
cluster_slots_assigned:16384
cluster_slots_ok:16384
cluster_slots_pfail:0
cluster_slots_fail:0
cluster_known_nodes:7
cluster_size:3
cluster_current_epoch:8
cluster_my_epoch:1
cluster_stats_messages_ping_sent:17442
cluster_stats_messages_pong_sent:13318
cluster_stats_messages_fail_sent:4
cluster_stats_messages_auth-ack_sent:1
cluster_stats_messages_sent:30765
cluster_stats_messages_ping_received:13311
cluster_stats_messages_pong_received:13367
cluster_stats_messages_meet_received:7
cluster_stats_messages_fail_received:1
cluster_stats_messages_auth-req_received:1
cluster_stats_messages_received:26687

1.3、#在新的master上重新分配槽位
#新的node节点加到集群之后,默认是master节点，但是没有slots，需要重新分配
#添加主机之后需要对添加至集群种的新主机重新分片,否则其没有分片也就无法写入数据。
#注意: 重新分配槽位需要清空数据,所以需要先备份数据,扩展后再恢复数据
[root@redis-node1 ~]#redis-cli -a 123456 --cluster reshard <当前任意集群节点>:6379
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
>>> Performing Cluster Check (using node 10.0.0.68:6379)
M: d6e2eca6b338b717923f64866bd31d42e52edc98 10.0.0.68:6379
   slots: (0 slots) master
M: d34da8666a6f587283a1c2fca5d13691407f9462 10.0.0.28:6379
   slots:[10923-16383] (5461 slots) master
   1 additional replica(s)
M: d04e524daec4d8e22bdada7f21a9487c2d3e1057 10.0.0.48:6379
   slots:[5461-10922] (5462 slots) master
   1 additional replica(s)
M: cb028b83f9dc463d732f6e76ca6bbcd469d948a7 10.0.0.8:6379
   slots:[0-5460] (5461 slots) master
   1 additional replica(s)
S: 99720241248ff0e4c6fa65c2385e92468b3b5993 10.0.0.18:6379
   slots: (0 slots) slave
   replicates d04e524daec4d8e22bdada7f21a9487c2d3e1057
M: f67f1c02c742cd48d3f48d8c362f9f1b9aa31549 10.0.0.78:6379
   slots: (0 slots) master
S: f9adcfb8f5a037b257af35fa548a26ffbadc852d 10.0.0.38:6379
   slots: (0 slots) slave
   replicates cb028b83f9dc463d732f6e76ca6bbcd469d948a7
S: 9875b50925b4e4f29598e6072e5937f90df9fc71 10.0.0.58:6379
   slots: (0 slots) slave
   replicates d34da8666a6f587283a1c2fca5d13691407f9462
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
How many slots do you want to move (from 1 to 16384)?4096 #新分配多少个槽位=16384/master个数
What is the receiving node ID? d6e2eca6b338b717923f64866bd31d42e52edc98 #新的master的ID
Please enter all the source node IDs.
 Type 'all' to use all the nodes as source nodes for the hash slots.
 Type 'done' once you entered all the source nodes IDs.
Source node #1: all #将哪些源主机的槽位分配给新的节点，all是自动在所有的redis node选择划分，如果是从redis cluster删除某个主机可以使用此方式将指定主机上的槽位全部移动到别的redis主机
......
Do you want to proceed with the proposed reshard plan (yes/no)?  yes #确认分配
......
Moving slot 12280 from 10.0.0.28:6379 to 10.0.0.68:6379: .
Moving slot 12281 from 10.0.0.28:6379 to 10.0.0.68:6379: .
Moving slot 12282 from 10.0.0.28:6379 to 10.0.0.68:6379: 
Moving slot 12283 from 10.0.0.28:6379 to 10.0.0.68:6379: ..
Moving slot 12284 from 10.0.0.28:6379 to 10.0.0.68:6379: 
Moving slot 12285 from 10.0.0.28:6379 to 10.0.0.68:6379: .
Moving slot 12286 from 10.0.0.28:6379 to 10.0.0.68:6379: 
Moving slot 12287 from 10.0.0.28:6379 to 10.0.0.68:6379: ..
[root@redis-node1 ~]# #确定slot分配成功
[root@redis-node1 ~]#redis-cli -a 123456 --cluster check 10.0.0.8:6379
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
10.0.0.8:6379 (cb028b83...) -> 5019 keys | 4096 slots | 1 slaves.
10.0.0.68:6379 (d6e2eca6...) -> 4948 keys | 4096 slots | 0 slaves.
10.0.0.48:6379 (d04e524d...) -> 5033 keys | 4096 slots | 1 slaves.
10.0.0.28:6379 (d34da866...) -> 5000 keys | 4096 slots | 1 slaves.
[OK] 20000 keys in 5 masters.
1.22 keys per slot on average.
>>> Performing Cluster Check (using node 10.0.0.8:6379)
M: cb028b83f9dc463d732f6e76ca6bbcd469d948a7 10.0.0.8:6379
   slots:[1365-5460] (4096 slots) master
   1 additional replica(s)
M: d6e2eca6b338b717923f64866bd31d42e52edc98 10.0.0.68:6379
   slots:[0-1364],[5461-6826],[10923-12287] (4096 slots) master #可看到4096个slots
S: 9875b50925b4e4f29598e6072e5937f90df9fc71 10.0.0.58:6379
   slots: (0 slots) slave
   replicates d34da8666a6f587283a1c2fca5d13691407f9462
S: f9adcfb8f5a037b257af35fa548a26ffbadc852d 10.0.0.38:6379
   slots: (0 slots) slave
   replicates cb028b83f9dc463d732f6e76ca6bbcd469d948a7
M: d04e524daec4d8e22bdada7f21a9487c2d3e1057 10.0.0.48:6379
   slots:[6827-10922] (4096 slots) master
   1 additional replica(s)
S: 99720241248ff0e4c6fa65c2385e92468b3b5993 10.0.0.18:6379
   slots: (0 slots) slave
   replicates d04e524daec4d8e22bdada7f21a9487c2d3e1057
M: d34da8666a6f587283a1c2fca5d13691407f9462 10.0.0.28:6379
   slots:[12288-16383] (4096 slots) master
   1 additional replica(s)
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

1.4、#为新的master添加新的slave节点
#需要再向当前的Redis集群中添加一个Redis单机服务器10.0.0.78，用于解决当前10.0.0.68单机的潜在宕机问题，即实现响应的高可用功能。有两种方式：

#方法1：在新加节点到集群时，直接将之设置为slave
#查看当前状态
[root@redis-node1 ~]#redis-cli -a 123456 --cluster check 10.0.0.8:6379
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
10.0.0.8:6379 (cb028b83...) -> 5019 keys | 4096 slots | 1 slaves.
10.0.0.68:6379 (d6e2eca6...) -> 4948 keys | 4096 slots | 0 slaves.
10.0.0.48:6379 (d04e524d...) -> 5033 keys | 4096 slots | 1 slaves.
10.0.0.28:6379 (d34da866...) -> 5000 keys | 4096 slots | 1 slaves.
[OK] 20000 keys in 4 masters.
1.22 keys per slot on average.
>>> Performing Cluster Check (using node 10.0.0.8:6379)
M: cb028b83f9dc463d732f6e76ca6bbcd469d948a7 10.0.0.8:6379
   slots:[1365-5460] (4096 slots) master
   1 additional replica(s)
M: d6e2eca6b338b717923f64866bd31d42e52edc98 10.0.0.68:6379
   slots:[0-1364],[5461-6826],[10923-12287] (4096 slots) master
S: 9875b50925b4e4f29598e6072e5937f90df9fc71 10.0.0.58:6379
   slots: (0 slots) slave
   replicates d34da8666a6f587283a1c2fca5d13691407f9462
S: f9adcfb8f5a037b257af35fa548a26ffbadc852d 10.0.0.38:6379
   slots: (0 slots) slave
   replicates cb028b83f9dc463d732f6e76ca6bbcd469d948a7
M: d04e524daec4d8e22bdada7f21a9487c2d3e1057 10.0.0.48:6379
   slots:[6827-10922] (4096 slots) master
   1 additional replica(s)
S: 99720241248ff0e4c6fa65c2385e92468b3b5993 10.0.0.18:6379
   slots: (0 slots) slave
   replicates d04e524daec4d8e22bdada7f21a9487c2d3e1057
M: d34da8666a6f587283a1c2fca5d13691407f9462 10.0.0.28:6379
   slots:[12288-16383] (4096 slots) master
   1 additional replica(s)
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
#直接加为slave节点
[root@redis-node1 ~]#redis-cli -a 123456 --cluster add-node 10.0.0.78:6379 10.0.0.8:6379 --cluster-slave --cluster-master-id d6e2eca6b338b717923f64866bd31d42e52edc98

#验证是否成功
[root@redis-node1 ~]#redis-cli -a 123456 --cluster check 10.0.0.8:6379
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
10.0.0.8:6379 (cb028b83...) -> 5019 keys | 4096 slots | 1 slaves.
10.0.0.68:6379 (d6e2eca6...) -> 4948 keys | 4096 slots | 1 slaves.
10.0.0.48:6379 (d04e524d...) -> 5033 keys | 4096 slots | 1 slaves.
10.0.0.28:6379 (d34da866...) -> 5000 keys | 4096 slots | 1 slaves.
[OK] 20000 keys in 4 masters.
1.22 keys per slot on average.
>>> Performing Cluster Check (using node 10.0.0.8:6379)
M: cb028b83f9dc463d732f6e76ca6bbcd469d948a7 10.0.0.8:6379
   slots:[1365-5460] (4096 slots) master
   1 additional replica(s)
M: d6e2eca6b338b717923f64866bd31d42e52edc98 10.0.0.68:6379
   slots:[0-1364],[5461-6826],[10923-12287] (4096 slots) master
   1 additional replica(s)
S: 36840d7eea5835ba540d9b64ec018aa3f8de6747 10.0.0.78:6379
   slots: (0 slots) slave
   replicates d6e2eca6b338b717923f64866bd31d42e52edc98
S: 9875b50925b4e4f29598e6072e5937f90df9fc71 10.0.0.58:6379
   slots: (0 slots) slave
 replicates d34da8666a6f587283a1c2fca5d13691407f9462
S: f9adcfb8f5a037b257af35fa548a26ffbadc852d 10.0.0.38:6379
   slots: (0 slots) slave
   replicates cb028b83f9dc463d732f6e76ca6bbcd469d948a7
M: d04e524daec4d8e22bdada7f21a9487c2d3e1057 10.0.0.48:6379
   slots:[6827-10922] (4096 slots) master
   1 additional replica(s)
S: 99720241248ff0e4c6fa65c2385e92468b3b5993 10.0.0.18:6379
   slots: (0 slots) slave
   replicates d04e524daec4d8e22bdada7f21a9487c2d3e1057
M: d34da8666a6f587283a1c2fca5d13691407f9462 10.0.0.28:6379
   slots:[12288-16383] (4096 slots) master
   1 additional replica(s)
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
[root@centos8 ~]#redis-cli -a 123456 -h 10.0.0.8 --no-auth-warning cluster info 
cluster_state:ok
cluster_slots_assigned:16384
cluster_slots_ok:16384
cluster_slots_pfail:0
cluster_slots_fail:0
cluster_known_nodes:8   #8个节点
cluster_size:4          #4组主从
cluster_current_epoch:11
cluster_my_epoch:10
cluster_stats_messages_ping_sent:1810
cluster_stats_messages_pong_sent:1423
cluster_stats_messages_auth-req_sent:5
cluster_stats_messages_update_sent:14
cluster_stats_messages_sent:3252
cluster_stats_messages_ping_received:1417
cluster_stats_messages_pong_received:1368
cluster_stats_messages_meet_received:2
cluster_stats_messages_fail_received:2
cluster_stats_messages_auth-ack_received:2
cluster_stats_messages_update_received:4
cluster_stats_messages_received:2795

#方法2：先将新节点加入集群，再修改为slave

#为新的master添加slave节点
#把10.0.0.78:6379添加到集群中：
[root@redis-node1 ~]#redis-cli -a 123456 --cluster add-node 10.0.0.78:6379 10.0.0.8:6379

#更改新节点更改状态为slave：
#需要手动将其指定为某个master的slave，否则其默认角色为master。
[root@redis-node1 ~]#redis-cli -h 10.0.0.78 -p 6379 -a 123456 #登录到新添加节点
10.0.0.78:6380> CLUSTER NODES #查看当前集群节点，找到目标master 的ID
10.0.0.78:6380> CLUSTER REPLICATE 886338acd50c3015be68a760502b239f4509881c #将其设置slave，命令格式为cluster replicate MASTERID
10.0.0.78:6380> CLUSTER NODES #再次查看集群节点状态，验证节点是否已经更改为指定master 的slave

2、Redis Cluster缩容（Redis 5为例）
	由于10.0.0.8服务器使用年限已经超过三年，已经超过厂商质保期而且硬盘出现异常报警，经运维部架构师提交方案并同开发同事开会商议，决定将现有Redis集群的8台主服务器中的master 10.0.0.8和对应的slave 10.0.0.38 临时下线，三台服务器的并发写入性能足够支出未来1-2年的业务需求。
	删除节点过程：
	添加节点的时候是先添加node节点到集群，然后分配槽位，删除节点的操作与添加节点的操作正好相反，是先将被删除的Redis node上的槽位迁移到集群中的其他Redis node节点上，然后再将其删除，如果一个Redis node节点上的槽位没有被完全迁移，删除该node的时候会提示有数据且无法删除。

2.1、迁移master 的槽位之其他master
注意: 被迁移Redis master源服务器必须保证没有数据，否则迁移报错并会被强制中断。
#查看当前状态
[root@redis-node1 ~]#redis-cli -a 123456 --cluster check 10.0.0.8:6379
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
10.0.0.8:6379 (cb028b83...) -> 5019 keys | 4096 slots | 1 slaves.
10.0.0.68:6379 (d6e2eca6...) -> 4948 keys | 4096 slots | 1 slaves.
10.0.0.48:6379 (d04e524d...) -> 5033 keys | 4096 slots | 1 slaves.
10.0.0.28:6379 (d34da866...) -> 5000 keys | 4096 slots | 1 slaves.
[OK] 20000 keys in 4 masters.
1.22 keys per slot on average.
>>> Performing Cluster Check (using node 10.0.0.8:6379)
M: cb028b83f9dc463d732f6e76ca6bbcd469d948a7 10.0.0.8:6379
   slots:[1365-5460] (4096 slots) master
   1 additional replica(s)
M: d6e2eca6b338b717923f64866bd31d42e52edc98 10.0.0.68:6379
   slots:[0-1364],[5461-6826],[10923-12287] (4096 slots) master
   1 additional replica(s)
S: 36840d7eea5835ba540d9b64ec018aa3f8de6747 10.0.0.78:6379
   slots: (0 slots) slave
   replicates d6e2eca6b338b717923f64866bd31d42e52edc98
S: 9875b50925b4e4f29598e6072e5937f90df9fc71 10.0.0.58:6379
   slots: (0 slots) slave
  replicates d34da8666a6f587283a1c2fca5d13691407f9462
S: f9adcfb8f5a037b257af35fa548a26ffbadc852d 10.0.0.38:6379
   slots: (0 slots) slave
   replicates cb028b83f9dc463d732f6e76ca6bbcd469d948a7
M: d04e524daec4d8e22bdada7f21a9487c2d3e1057 10.0.0.48:6379
   slots:[6827-10922] (4096 slots) master
   1 additional replica(s)
S: 99720241248ff0e4c6fa65c2385e92468b3b5993 10.0.0.18:6379
   slots: (0 slots) slave
   replicates d04e524daec4d8e22bdada7f21a9487c2d3e1057
M: d34da8666a6f587283a1c2fca5d13691407f9462 10.0.0.28:6379
   slots:[12288-16383] (4096 slots) master
   1 additional replica(s)
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
#连接到任意集群节点，#最后1365个slot从10.0.0.8移动到第一个master节点10.0.0.28上
[root@redis-node1 ~]#redis-cli -a 123456 --cluster reshard 10.0.0.18:6379
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
>>> Performing Cluster Check (using node 10.0.0.18:6379)
S: 99720241248ff0e4c6fa65c2385e92468b3b5993 10.0.0.18:6379
   slots: (0 slots) slave
   replicates d04e524daec4d8e22bdada7f21a9487c2d3e1057
S: f9adcfb8f5a037b257af35fa548a26ffbadc852d 10.0.0.38:6379
   slots: (0 slots) slave
   replicates cb028b83f9dc463d732f6e76ca6bbcd469d948a7
S: 36840d7eea5835ba540d9b64ec018aa3f8de6747 10.0.0.78:6379
   slots: (0 slots) slave
   replicates d6e2eca6b338b717923f64866bd31d42e52edc98
M: cb028b83f9dc463d732f6e76ca6bbcd469d948a7 10.0.0.8:6379
   slots:[1365-5460] (4096 slots) master
   1 additional replica(s)
M: d6e2eca6b338b717923f64866bd31d42e52edc98 10.0.0.68:6379
   slots:[0-1364],[5461-6826],[10923-12287] (4096 slots) master
   1 additional replica(s)
S: 9875b50925b4e4f29598e6072e5937f90df9fc71 10.0.0.58:6379
   slots: (0 slots) slave
   replicates d34da8666a6f587283a1c2fca5d13691407f9462
M: d04e524daec4d8e22bdada7f21a9487c2d3e1057 10.0.0.48:6379
   slots:[6827-10922] (4096 slots) master
   1 additional replica(s)
M: d34da8666a6f587283a1c2fca5d13691407f9462 10.0.0.28:6379
   slots:[12288-16383] (4096 slots) master
   1 additional replica(s)
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
How many slots do you want to move (from 1 to 16384)? 1356 #共4096/3分别给其它三个
master节点
What is the receiving node ID? d34da8666a6f587283a1c2fca5d13691407f9462 #master 
10.0.0.28
Please enter all the source node IDs.
 Type 'all' to use all the nodes as source nodes for the hash slots.
 Type 'done' once you entered all the source nodes IDs.
 Source node #1: cb028b83f9dc463d732f6e76ca6bbcd469d948a7 #输入要删除10.0.0.8节点ID
Source node #2: done
Ready to move 1356 slots.
 Source nodes:
   M: cb028b83f9dc463d732f6e76ca6bbcd469d948a7 10.0.0.8:6379
       slots:[1365-5460] (4096 slots) master
       1 additional replica(s)
 Destination node:
   M: d34da8666a6f587283a1c2fca5d13691407f9462 10.0.0.28:6379
       slots:[12288-16383] (4096 slots) master
       1 additional replica(s)
 Resharding plan:
   Moving slot 1365 from cb028b83f9dc463d732f6e76ca6bbcd469d948a7
......
 Moving slot 2719 from cb028b83f9dc463d732f6e76ca6bbcd469d948a7
   Moving slot 2720 from cb028b83f9dc463d732f6e76ca6bbcd469d948a7
Do you want to proceed with the proposed reshard plan (yes/no)? yes #确定
......
Moving slot 2718 from 10.0.0.8:6379 to 10.0.0.28:6379: ..
Moving slot 2719 from 10.0.0.8:6379 to 10.0.0.28:6379: .
Moving slot 2720 from 10.0.0.8:6379 to 10.0.0.28:6379: ..
#非交互式方式
#再将1365个slot从10.0.0.8移动到第二个master节点10.0.0.48上
[root@redis-node1 ~]#redis-cli -a 123456 --cluster reshard 10.0.0.18:6379 --
cluster-slots 1365 --cluster-from cb028b83f9dc463d732f6e76ca6bbcd469d948a7 --
cluster-to d04e524daec4d8e22bdada7f21a9487c2d3e1057 --cluster-yes
#最后的slot从10.0.0.8移动到第三个master节点10.0.0.68上
[root@redis-node1 ~]#redis-cli -a 123456 --cluster reshard 10.0.0.18:6379 --
cluster-slots 1375 --cluster-from cb028b83f9dc463d732f6e76ca6bbcd469d948a7 --
cluster-to d6e2eca6b338b717923f64866bd31d42e52edc98 --cluster-yes
#确认10.0.0.8的所有slot都移走了，上面的slave也自动删除，成为其它master的slave 
[root@redis-node1 ~]#redis-cli -a 123456 --cluster check 10.0.0.8:6379
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
10.0.0.8:6379 (cb028b83...) -> 0 keys | 0 slots | 0 slaves.
10.0.0.68:6379 (d6e2eca6...) -> 6631 keys | 5471 slots | 2 slaves.
10.0.0.48:6379 (d04e524d...) -> 6694 keys | 5461 slots | 1 slaves.
10.0.0.28:6379 (d34da866...) -> 6675 keys | 5452 slots | 1 slaves.
[OK] 20000 keys in 4 masters.
1.22 keys per slot on average.
>>> Performing Cluster Check (using node 10.0.0.8:6379)
M: cb028b83f9dc463d732f6e76ca6bbcd469d948a7 10.0.0.8:6379
   slots: (0 slots) master
M: d6e2eca6b338b717923f64866bd31d42e52edc98 10.0.0.68:6379
   slots:[0-1364],[4086-6826],[10923-12287] (5471 slots) master
   2 additional replica(s)
S: 36840d7eea5835ba540d9b64ec018aa3f8de6747 10.0.0.78:6379
   slots: (0 slots) slave
   replicates d6e2eca6b338b717923f64866bd31d42e52edc98
S: 9875b50925b4e4f29598e6072e5937f90df9fc71 10.0.0.58:6379
   slots: (0 slots) slave
   replicates d34da8666a6f587283a1c2fca5d13691407f9462
S: f9adcfb8f5a037b257af35fa548a26ffbadc852d 10.0.0.38:6379
   slots: (0 slots) slave
    replicates d6e2eca6b338b717923f64866bd31d42e52edc98
M: d04e524daec4d8e22bdada7f21a9487c2d3e1057 10.0.0.48:6379
   slots:[2721-4085],[6827-10922] (5461 slots) master
   1 additional replica(s)
S: 99720241248ff0e4c6fa65c2385e92468b3b5993 10.0.0.18:6379
   slots: (0 slots) slave
   replicates d04e524daec4d8e22bdada7f21a9487c2d3e1057
M: d34da8666a6f587283a1c2fca5d13691407f9462 10.0.0.28:6379
   slots:[1365-2720],[12288-16383] (5452 slots) master
   1 additional replica(s)
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
#原有的10.0.0.38自动成为10.0.0.68的slave
[root@redis-node1 ~]#redis-cli -a 123456 -h 10.0.0.68 INFO replication
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
# Replication
role:master
connected_slaves:2
slave0:ip=10.0.0.78,port=6379,state=online,offset=129390,lag=0
slave1:ip=10.0.0.38,port=6379,state=online,offset=129390,lag=0
master_replid:43e3e107a0acb1fd5a97240fc4b2bd8fc85b113f
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:129404
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:129404
[root@centos8 ~]#redis-cli -a 123456 -h 10.0.0.8 --no-auth-warning cluster info 
cluster_state:ok
cluster_slots_assigned:16384
cluster_slots_ok:16384
cluster_slots_pfail:0
cluster_slots_fail:0
cluster_known_nodes:8  #集群中8个节点
cluster_size:3       #少了一个主从的slot
cluster_current_epoch:16
cluster_my_epoch:13
cluster_stats_messages_ping_sent:3165
cluster_stats_messages_pong_sent:2489
cluster_stats_messages_fail_sent:6
cluster_stats_messages_auth-req_sent:5
cluster_stats_messages_auth-ack_sent:1
cluster_stats_messages_update_sent:27
cluster_stats_messages_sent:5693
cluster_stats_messages_ping_received:2483
cluster_stats_messages_pong_received:2400
cluster_stats_messages_meet_received:2
cluster_stats_messages_fail_received:2
cluster_stats_messages_auth-req_received:1
cluster_stats_messages_auth-ack_received:2
cluster_stats_messages_update_received:4
cluster_stats_messages_received:4894

2.2、从集群删除服务器
虽然槽位已经迁移完成，但是服务器IP信息还在集群当中，因此还需要将IP信息从集群删除
注意: 删除服务器前,必须清除主机上面的槽位,否则会删除主机失败
[root@redis-node1 ~]#redis-cli -a 123456 --cluster del-node 10.0.0.8:6379 
cb028b83f9dc463d732f6e76ca6bbcd469d948a7
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
>>> Removing node cb028b83f9dc463d732f6e76ca6bbcd469d948a7 from cluster 
10.0.0.8:6379
>>> Sending CLUSTER FORGET messages to the cluster...
>>> SHUTDOWN the node. #删除节点后,redis进程自动关闭
#删除节点信息
[root@redis-node1 ~]#rm -f /var/lib/redis/nodes-6379.conf

2.3、删除多余的slave节点验证结果
#验证删除成功
[root@redis-node1 ~]#ss -ntl
State       Recv-Q       Send-Q   Local Address:Port     Peer Address:Port   
     
LISTEN       0             128            0.0.0.0:22             0.0.0.0:*       
    
LISTEN       0             128               [::]:22               [::]:*  
[root@redis-node1 ~]#redis-cli -a 123456 --cluster check 10.0.0.18:6379 
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
10.0.0.68:6379 (d6e2eca6...) -> 6631 keys | 5471 slots | 2 slaves.
10.0.0.48:6379 (d04e524d...) -> 6694 keys | 5461 slots | 1 slaves.
10.0.0.28:6379 (d34da866...) -> 6675 keys | 5452 slots | 1 slaves.
[OK] 20000 keys in 3 masters.
1.22 keys per slot on average.
>>> Performing Cluster Check (using node 10.0.0.18:6379)
S: 99720241248ff0e4c6fa65c2385e92468b3b5993 10.0.0.18:6379
   slots: (0 slots) slave
   replicates d04e524daec4d8e22bdada7f21a9487c2d3e1057
S: f9adcfb8f5a037b257af35fa548a26ffbadc852d 10.0.0.38:6379
   slots: (0 slots) slave
   replicates d6e2eca6b338b717923f64866bd31d42e52edc98
S: 36840d7eea5835ba540d9b64ec018aa3f8de6747 10.0.0.78:6379
 slots: (0 slots) slave
   replicates d6e2eca6b338b717923f64866bd31d42e52edc98
M: d6e2eca6b338b717923f64866bd31d42e52edc98 10.0.0.68:6379
   slots:[0-1364],[4086-6826],[10923-12287] (5471 slots) master
   2 additional replica(s)
S: 9875b50925b4e4f29598e6072e5937f90df9fc71 10.0.0.58:6379
   slots: (0 slots) slave
   replicates d34da8666a6f587283a1c2fca5d13691407f9462
M: d04e524daec4d8e22bdada7f21a9487c2d3e1057 10.0.0.48:6379
   slots:[2721-4085],[6827-10922] (5461 slots) master
   1 additional replica(s)
M: d34da8666a6f587283a1c2fca5d13691407f9462 10.0.0.28:6379
   slots:[1365-2720],[12288-16383] (5452 slots) master
   1 additional replica(s)
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
#删除多余的slave从节点
[root@redis-node1 ~]#redis-cli -a 123456 --cluster del-node 10.0.0.18:6379 
f9adcfb8f5a037b257af35fa548a26ffbadc852d
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
>>> Removing node f9adcfb8f5a037b257af35fa548a26ffbadc852d from cluster 
10.0.0.18:6379
>>> Sending CLUSTER FORGET messages to the cluster...
>>> SHUTDOWN the node. #删除集群文件
[root@redis-node4 ~]#rm -f /var/lib/redis/nodes-6379.conf 
[root@redis-node1 ~]#redis-cli -a 123456 --cluster check 10.0.0.18:6379 
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
10.0.0.68:6379 (d6e2eca6...) -> 6631 keys | 5471 slots | 1 slaves.
10.0.0.48:6379 (d04e524d...) -> 6694 keys | 5461 slots | 1 slaves.
10.0.0.28:6379 (d34da866...) -> 6675 keys | 5452 slots | 1 slaves.
[OK] 20000 keys in 3 masters.
1.22 keys per slot on average.
>>> Performing Cluster Check (using node 10.0.0.18:6379)
S: 99720241248ff0e4c6fa65c2385e92468b3b5993 10.0.0.18:6379
   slots: (0 slots) slave
   replicates d04e524daec4d8e22bdada7f21a9487c2d3e1057
S: 36840d7eea5835ba540d9b64ec018aa3f8de6747 10.0.0.78:6379
   slots: (0 slots) slave
   replicates d6e2eca6b338b717923f64866bd31d42e52edc98
M: d6e2eca6b338b717923f64866bd31d42e52edc98 10.0.0.68:6379
   slots:[0-1364],[4086-6826],[10923-12287] (5471 slots) master
   1 additional replica(s)
S: 9875b50925b4e4f29598e6072e5937f90df9fc71 10.0.0.58:6379
   slots: (0 slots) slave
   replicates d34da8666a6f587283a1c2fca5d13691407f9462
M: d04e524daec4d8e22bdada7f21a9487c2d3e1057 10.0.0.48:6379
   slots:[2721-4085],[6827-10922] (5461 slots) master
   1 additional replica(s)
M: d34da8666a6f587283a1c2fca5d13691407f9462 10.0.0.28:6379
 slots:[1365-2720],[12288-16383] (5452 slots) master
   1 additional replica(s)
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
[root@redis-node1 ~]#redis-cli -a 123456 --cluster info 10.0.0.18:6379 
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
10.0.0.68:6379 (d6e2eca6...) -> 6631 keys | 5471 slots | 1 slaves.
10.0.0.48:6379 (d04e524d...) -> 6694 keys | 5461 slots | 1 slaves.
10.0.0.28:6379 (d34da866...) -> 6675 keys | 5452 slots | 1 slaves.
[OK] 20000 keys in 3 masters.
1.22 keys per slot on average.
#查看集群信息
[root@redis-node1 ~]#redis-cli -a 123456 -h 10.0.0.18 CLUSTER INFO
Warning: Using a password with '-a' or '-u' option on the command line interface 
may not be safe.
cluster_state:ok
cluster_slots_assigned:16384
cluster_slots_ok:16384
cluster_slots_pfail:0
cluster_slots_fail:0
cluster_known_nodes:6  #只有6个节点
cluster_size:3
cluster_current_epoch:11
cluster_my_epoch:10
cluster_stats_messages_ping_sent:12147
cluster_stats_messages_pong_sent:12274
cluster_stats_messages_update_sent:14
cluster_stats_messages_sent:24435
cluster_stats_messages_ping_received:12271
cluster_stats_messages_pong_received:12147
cluster_stats_messages_meet_received:3
cluster_stats_messages_update_received:28
cluster_stats_messages_received:24449