redis动态选库 redis选举

Redis集群节点的选举:

    当master挂掉之后，就会在该集群中的slave中选取一个来代替mater角色，

    从而保证redis集群slot的完整性。

    如果其中一个mster和它的slave都挂掉后，会导致slot不完整，整个集群都会挂掉。

集群节点信息：

192.168.2.200:6379> cluster nodes
192.168.2.201:6379
192.168.2.201:6380
192.168.2.200:6380
192.168.2.200:6379
192.168.2.100:6380
192.168.2.100:6379

新建3个key：

 

192.168.2.200:6379> set name zhangsan
    OK
    192.168.2.200:6379> set age 26
    -> Redirected to slot [741] located at 192.168.2.100:6379
    OK
    192.168.2.100:6379> set home beijing
    -> Redirected to slot [10814] located at 192.168.2.200:6379
    OK

模拟192.168.2.100:6379挂掉：

# ps -ef |grep redis
        root      19023      1  0 15:05 ?        00:00:01 redis-server 192.168.2.100:6379 [cluster]
        root      19030      1  0 15:05 ?        00:00:01 redis-server 192.168.2.100:6380 [cluster]
        root      19127   2912  0 15:13 pts/0    00:00:00 grep --color=auto redis
    # kill 19023

查看集群节点状态：（可以看到集群中的一个slave的角色变成了master）

 

# redis-trib.rb check 192.168.2.200:6379
    >>> Performing Cluster Check (using node 192.168.2.200:6379)
192.168.2.200:6379
master
    1 additional replica(s)
192.168.2.201:6379
master
    1 additional replica(s)
192.168.2.201:6380
slave
    replicates 3ff3a74f9dc41f8bc635ab845ad76bf77ffb0f69
    M: 227f51028bbe827f27b4e40ed7a08fcc7d8df969 192.168.2.200:6380
    slots:0-5460 (5461 slots) master
    0 additional replica(s)
192.168.2.100:6380
slave
    replicates 5844b4272c39456b0fdf73e384ff8c479547de47
    [OK] All nodes agree about slots configuration.
    >>> Check for open slots...
    >>> Check slots coverage...
    [OK] All 16384 slots covered.

查看数据是否存在：

# redis-cli -h 192.168.2.200 -p 6380 -c
        192.168.2.200:6380> keys *
        1) "age"

模拟恢复故障节点：

# redis-server redis.conf

查看集群节点状态：（故障节点恢复后，是变成master还是slave？）

# redis-trib.rb check 192.168.2.200:6379
    >>> Performing Cluster Check (using node 192.168.2.200:6379)
192.168.2.200:6379
master
   1 additional replica(s)
192.168.2.201:6379
master
   1 additional replica(s)
192.168.2.201:6380
slave
   replicates 3ff3a74f9dc41f8bc635ab845ad76bf77ffb0f69
192.168.2.200:6380
master
   1 additional replica(s)
 192.168.2.100:6380
slave
   replicates 5844b4272c39456b0fdf73e384ff8c479547de47
    S: 098e7eb756b6047fde988ab3c0b7189e1724ecf5 192.168.2.100:6379
 slave
   replicates 227f51028bbe827f27b4e40ed7a08fcc7d8df969
    [OK] All nodes agree about slots configuration.
    >>> Check for open slots...
    >>> Check slots coverage...
    [OK] All 16384 slots covered.

总结：master：192.168.2.100:6379 宕机后，

      slave：192.168.2.200:6380 代替了其位置，变成了master角色。

      当192.168.2.100:6379故障恢复后，并没有恢复到master的角色，

      而是充当了slave角色。

转载于:https://blog.51cto.com/13690439/2119973