集群维护之动态缩容
实战案例：
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。
迁移master 的槽位之其他master
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。
Redis4 版本
[root@redis-node1 ~]# redis-trib.rb reshard 10.0.0.8:6379
[root@redis-node1 ~]# redis-trib.rb fix 10.0.0.8:6379 #如果迁移失败使用此命令修复集群Redis 5版本
#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: ..
#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
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
Redis 3/4：
[root@s~]#redis-trib.rb del-node 10.0.0.8:6379 dfffc371085859f2858730e1f350e9167e287073
>>> Removing node dfffc371085859f2858730e1f350e9167e287073 from cluster
192.168.7.102:6379
>>> Sending CLUSTER FORGET messages to the cluster...
>>> SHUTDOWN the node.Redis 5：
[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.
#删除节点信息
[root@redis-node1 ~]#rm -f /var/lib/redis/nodes-6379.conf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
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