服务器重启后，集群报错：
[root@SHH-HQ-NHS11S nhsuser]# redis-cli -c -h ip -p 7000
ip:7000> set cc dd
(error) CLUSTERDOWN Hash slot not served
检查集群节点情况
> cluster nodes
c0767666bee76e5e0dc67f24031a3e1b574235cc :7000@17000 myself,master – 0 0 0 connected
发现集群的节点只剩一个，其余节点都不见了。
将集群节点加入：
# redis-cli --cluster add-node ip: ip:
>>> Adding node ip: to cluster ip:
>>> Performing Cluster Check (using node ip:)
M: c0767666bee76e5e0dc67f24031a3e1b574235cc ip:
slots: ( slots) master
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[ERR] Not all slots are covered by nodes.
这个往往是由于主node移除了，但是并没有移除node上面的slot，从而导致了slot总数没有达到16384，其实也就是slots分布不正确。所以在删除节点的时候一定要注意删除的是否是Master主节点。现在这样情况，我们先修复集群：
# redis-cli --cluster fix IP:7000
>>> Covering slot 9675 with ip:7000
有点久,稍等下
然后检查修复情况:
# redis-cli --cluster check ip:
ip: (c0767666...) -> keys | slots | slaves.
[OK] keys in masters.
0.00 keys per slot on average.
>>> Performing Cluster Check (using node ip:)
M: c0767666bee76e5e0dc67f24031a3e1b574235cc IP:
slots:[-] ( slots) master
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All slots covered.
将节点加入集群:
[root@SHH-HQ-NHS11S nhsuser]# redis-cli --cluster add-node ip: ip:
>>> Adding node ip: to cluster ip:
>>> Performing Cluster Check (using node ip:)
M: c0767666bee76e5e0dc67f24031a3e1b574235cc ip:
slots:[-] ( slots) master
M: a98432e520af41117f5d8a81e2c0e2a430940c7e ip:
slots: ( slots) master
M: 2ff0c7ee051e26f484b6826d6aa8a5a3fbc93d17 ip:
slots: ( slots) master
M: 26bf8ce786d7c9d0bbb9d9d78978497f86fbbe0a ip:
slots: ( slots) master
M: 0a7718d2c53a16debdbfb391a7acd23a50a05faa ip:
slots: ( slots) master
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All slots covered.
>>> Send CLUSTER MEET to node ip: to make it join the cluster.
[OK] New node added correctly.
测试一把：
[root@SHH-HQ-NHS11S nhsuser]# redis-cli -c -h IP -p
IP:> set aa dd
OK
IP:> get aa
"dd"
IP:>
