Redis 内置客户端redis-cli通过--cluster选项集成了多个 Redis 集群管理工具， 这些工具可以执行创建集群、向集群中添加或移除节点、对集群实施重分片以及负载均衡等操作， 它们每一个都非常强大：
$ redis-cli --cluster help
Cluster Manager Commands:
create host1:port1 ... hostN:portN
--cluster-replicas <arg>
check host:port
info host:port
fix host:port
reshard host:port
--cluster-from <arg>
--cluster-to <arg>
--cluster-slots <arg>
--cluster-yes
--cluster-timeout <arg>
--cluster-pipeline <arg>
rebalance host:port
--cluster-weight <node1=w1...nodeN=wN>
--cluster-use-empty-masters
--cluster-timeout <arg>
--cluster-simulate
--cluster-pipeline <arg>
--cluster-threshold <arg>
add-node new_host:new_port existing_host:existing_port
--cluster-slave
--cluster-master-id <arg>
del-node host:port node_id
call host:port command arg arg .. arg
set-timeout host:port milliseconds
import host:port
--cluster-from <arg>
--cluster-copy
--cluster-replace
help
For check, fix, reshard, del-node, set-timeout you can specify the host and port of any working node in the cluster.
本文将对上述工具的其中一些进行介绍， 帮助大家初步地了解这些工具的基本用法。
创建集群的工作可以通过create命令来完成， 用户只需要给定各个节点的地址以及想要设置的从服务器数量即可。 比如说， 通过执行以下命令， 我们可以创建出一个由三个主节点和三个从节点组成的集群：
$ redis-cli --cluster create 127.0.0.1:30001 127.0.0.1:30002 127.0.0.1:30003 127.0.0.1:30004 127.0.0.1:30005 127.0.0.1:30006 --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 127.0.0.1:30004 to 127.0.0.1:30001
Adding replica 127.0.0.1:30005 to 127.0.0.1:30002
Adding replica 127.0.0.1:30006 to 127.0.0.1:30003
>>> Trying to optimize slaves allocation for anti-affinity
[WARNING] Some slaves are in the same host as their master
M: 4979f8583676c46039672fb7319e917e4b303707 127.0.0.1:30001
slots:[0-5460] (5461 slots) master
M: 4ff303d96f5c7436ce8ce2fa6e306272e82cd454 127.0.0.1:30002
slots:[5461-10922] (5462 slots) master
M: 07e230805903e4e1657743a2e4d8811a59e2f32f 127.0.0.1:30003
slots:[10923-16383] (5461 slots) master
S: 4788fd4d92387fc5d38a2cd12f0c0d80fc0f6609 127.0.0.1:30004
replicates 4979f8583676c46039672fb7319e917e4b303707
S: b45a7f4355ea733a3177b89654c10f9c31092e92 127.0.0.1:30005
replicates 4ff303d96f5c7436ce8ce2fa6e306272e82cd454
S: 7c56ffba63e3758bc4c2e9b6a55caf294bb21650 127.0.0.1:30006
replicates 07e230805903e4e1657743a2e4d8811a59e2f32f
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 127.0.0.1:30001)
M: 4979f8583676c46039672fb7319e917e4b303707 127.0.0.1:30001
slots:[0-5460] (5461 slots) master
1 additional replica(s)
S: 4788fd4d92387fc5d38a2cd12f0c0d80fc0f6609 127.0.0.1:30004
slots: (0 slots) slave
replicates 4979f8583676c46039672fb7319e917e4b303707
S: b45a7f4355ea733a3177b89654c10f9c31092e92 127.0.0.1:30005
slots: (0 slots) slave
replicates 4ff303d96f5c7436ce8ce2fa6e306272e82cd454
S: 7c56ffba63e3758bc4c2e9b6a55caf294bb21650 127.0.0.1:30006
slots: (0 slots) slave
replicates 07e230805903e4e1657743a2e4d8811a59e2f32f
M: 4ff303d96f5c7436ce8ce2fa6e306272e82cd454 127.0.0.1:30002
slots:[5461-10922] (5462 slots) master
1 additional replica(s)
M: 07e230805903e4e1657743a2e4d8811a59e2f32f 127.0.0.1:30003
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.
通过执行info命令， 用户可以看到集群包含的主从节点数量， 以及集群中的键、槽分布信息：
$ redis-cli --cluster info 127.0.0.1:30001
127.0.0.1:30001 (4979f858...) -> 1 keys | 5461 slots | 1 slaves.
127.0.0.1:30002 (4ff303d9...) -> 4 keys | 5462 slots | 1 slaves.
127.0.0.1:30003 (07e23080...) -> 3 keys | 5461 slots | 1 slaves.
[OK] 8 keys in 3 masters.
0.00 keys per slot on average.
添加节点/移除节点
在拥有了集群之后， 用户就可以通过执行add-node命令或者del-node命令， 向集群里面添加新节点又或者移除已有的节点。
比如说， 通过执行以下命令， 我们可以把节点 30007 添加至集群当中：在此我向大家推荐一个架构学习交流裙。交流学习裙号：821169538，里面会分享一些资深架构师录制的视频录像
redis-cli --cluster add-node 127.0.0.1:30007 127.0.0.1:30001
>>> Adding node 127.0.0.1:30007 to cluster 127.0.0.1:30001
>>> Performing Cluster Check (using node 127.0.0.1:30001)
...
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
>>> Send CLUSTER MEET to node 127.0.0.1:30007 to make it join the cluster.
[OK] New node added correctly.
又或者通过执行以下命令， 将 ID 为e1971e...的节点 30007 移出集群：
redis-cli --cluster del-node 127.0.0.1:30001 e1971eef02709cf4698a6fcb09935a910982ab3b
>>> Removing node e1971eef02709cf4698a6fcb09935a910982ab3b from cluster 127.0.0.1:30001
>>> Sending CLUSTER FORGET messages to the cluster...
>>> SHUTDOWN the node.
通过执行reshard命令， 用户可以将指定数量的槽从一个节点迁移至另一个节点。 比如说， 通过执行以下命令， 我们可以将 ID 为4979f...的节点 30001 目前负责的其中 10 个槽转交给 ID 为1cd87d...的节点 30007 负责：
$ redis-cli --cluster reshard 127.0.0.1:30001 --cluster-from 4979f8583676c46039672fb7319e917e4b303707 --cluster-to 1cd87d132101893b7aa2b81cf333b2f7be9e1b75 --cluster-slots 10
>>> Performing Cluster Check (using node 127.0.0.1:30001)
M: 4979f8583676c46039672fb7319e917e4b303707 127.0.0.1:30001
slots:[0-5460] (5461 slots) master
1 additional replica(s)
S: 4788fd4d92387fc5d38a2cd12f0c0d80fc0f6609 127.0.0.1:30004
slots: (0 slots) slave
replicates 4979f8583676c46039672fb7319e917e4b303707
S: b45a7f4355ea733a3177b89654c10f9c31092e92 127.0.0.1:30005
slots: (0 slots) slave
replicates 4ff303d96f5c7436ce8ce2fa6e306272e82cd454
M: 1cd87d132101893b7aa2b81cf333b2f7be9e1b75 127.0.0.1:30007
slots: (0 slots) master
S: 7c56ffba63e3758bc4c2e9b6a55caf294bb21650 127.0.0.1:30006
slots: (0 slots) slave
replicates 07e230805903e4e1657743a2e4d8811a59e2f32f
M: 4ff303d96f5c7436ce8ce2fa6e306272e82cd454 127.0.0.1:30002
slots:[5461-10922] (5462 slots) master
1 additional replica(s)
M: 07e230805903e4e1657743a2e4d8811a59e2f32f 127.0.0.1:30003
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.
Ready to move 10 slots.
Source nodes:
M: 4979f8583676c46039672fb7319e917e4b303707 127.0.0.1:30001
slots:[0-5460] (5461 slots) master
1 additional replica(s)
Destination node:
M: 1cd87d132101893b7aa2b81cf333b2f7be9e1b75 127.0.0.1:30007
slots: (0 slots) master
Resharding plan:
Moving slot 0 from 4979f8583676c46039672fb7319e917e4b303707
Moving slot 1 from 4979f8583676c46039672fb7319e917e4b303707
Moving slot 2 from 4979f8583676c46039672fb7319e917e4b303707
Moving slot 3 from 4979f8583676c46039672fb7319e917e4b303707
Moving slot 4 from 4979f8583676c46039672fb7319e917e4b303707
Moving slot 5 from 4979f8583676c46039672fb7319e917e4b303707
Moving slot 6 from 4979f8583676c46039672fb7319e917e4b303707
Moving slot 7 from 4979f8583676c46039672fb7319e917e4b303707
Moving slot 8 from 4979f8583676c46039672fb7319e917e4b303707
Moving slot 9 from 4979f8583676c46039672fb7319e917e4b303707
Do you want to proceed with the proposed reshard plan (yes/no)? yes
Moving slot 0 from 127.0.0.1:30001 to 127.0.0.1:30007:
Moving slot 1 from 127.0.0.1:30001 to 127.0.0.1:30007:
Moving slot 2 from 127.0.0.1:30001 to 127.0.0.1:30007:
Moving slot 3 from 127.0.0.1:30001 to 127.0.0.1:30007:
Moving slot 4 from 127.0.0.1:30001 to 127.0.0.1:30007:
Moving slot 5 from 127.0.0.1:30001 to 127.0.0.1:30007:
Moving slot 6 from 127.0.0.1:30001 to 127.0.0.1:30007:
Moving slot 7 from 127.0.0.1:30001 to 127.0.0.1:30007:
Moving slot 8 from 127.0.0.1:30001 to 127.0.0.1:30007:
Moving slot 9 from 127.0.0.1:30001 to 127.0.0.1:30007:
当集群中各个节点的槽配置趋于不均衡的时候， 各个节点负担的载荷就可能会出现区别， 并导致某些节点超负荷运行， 而某些节点则长时间空置。 为了解决这个问题， 用户可以通过执行rebalance命令， 让各个节点负责的槽数量重新回到平均状态。
比如说， 对于以下这个由三个节点组成， 并且三个节点分别负责 2000 、 11384 和 3000 个槽的集群来说：
$ redis-cli --cluster info 127.0.0.1:30001
127.0.0.1:30001 (61d1f17b...) -> 0 keys | 2000 slots | 1 slaves.
127.0.0.1:30002 (101fbae9...) -> 0 keys | 11384 slots | 1 slaves.
127.0.0.1:30003 (31822e0a...) -> 0 keys | 3000 slots | 1 slaves.
[OK] 0 keys in 3 masters.
0.00 keys per slot on average.
我们可以通过执行以下命令来重新分配各个节点负责的槽：
$ redis-cli --cluster rebalance 127.0.0.1:30001
>>> Performing Cluster Check (using node 127.0.0.1:30001)
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
>>> Rebalancing across 3 nodes. Total weight = 3.00
Moving 3462 slots from 127.0.0.1:30002 to 127.0.0.1:30001
#####...#####
Moving 2461 slots from 127.0.0.1:30002 to 127.0.0.1:30003
#####...#####
在复杂均衡操作执行完毕之后， 集群各个节点负责的槽数量将趋于平均， 这样它们各自负担的载荷也会重新回到平均状态：
$ redis-cli --cluster info 127.0.0.1:30001
127.0.0.1:30001 (61d1f17b...) -> 0 keys | 5462 slots | 1 slaves.
127.0.0.1:30002 (101fbae9...) -> 0 keys | 5461 slots | 1 slaves.
127.0.0.1:30003 (31822e0a...) -> 0 keys | 5461 slots | 1 slaves.
[OK] 0 keys in 3 masters.
0.00 keys per slot on average.
在集群的所有节点中执行命令
如果用户想要对集群中的所有节点执行同一个命令， 那么可以通过call命令来完成。 比如说， 通过执行以下命令， 用户就可以让集群中的每个节点都执行DBSIZE命令， 从而得到各个节点各自的数据库大小：
$ redis-cli --cluster call 127.0.0.1:30001 DBSIZE
>>> Calling DBSIZE
127.0.0.1:30001: (integer) 0
127.0.0.1:30004: (integer) 0
127.0.0.1:30005: (integer) 3
127.0.0.1:30006: (integer) 0
127.0.0.1:30002: (integer) 3
127.0.0.1:30003: (integer) 0
好的， 关于redis-cli --cluster选项的简单介绍就到此结束了， 希望这些介绍可以帮助大家更好地了解到这些命令。 大家有兴趣的话， 也可以以此为起点， 更加深入地学习这些命令。
