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：
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。
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