Redis和Sentinel搭建一主多从高可用集群

本文将利用redis的sentinel，实现redis集群的高可用。

1.服务器规划

服务器资源规划如下表：

机器名	ip	redis port	redis status	sentinel port
m161p114	192.168.161.114	6379	master	26379
m161p115	192.168.161.115	6379	slave	26379
m162p203	192.168.162.203	6379	slave	26379

将搭建一个redis一主两从的主从复制集群，然后通过sentinel实现故障转移。

2.redis主从配置

redis主从配置详见Redis主从复制的配置过程.
在本文中，节点m161p114作为master节点，只需要在其他slave节点上，执行主从同步的命令即可。

127.0.0.1:6379> slaveof 192.168.161.114 6379
OK
127.0.0.1:6379> 

只需要在m161p115、m162p203两个节点执行上述的slaveof命令，就能组建一个以m161p114为master的redis集群。
之后通过info可以确认集群状态：
m161p115:

127.0.0.1:6379> info replication
# Replication
role:slave
master_host:192.168.161.114
master_port:6379
master_link_status:up
master_last_io_seconds_ago:0
master_sync_in_progress:0
slave_read_repl_offset:279743
slave_repl_offset:279743
slave_priority:100
slave_read_only:1
replica_announced:1
connected_slaves:0
master_failover_state:no-failover
master_replid:00bad10aad1b2ddde89253fd5c026c9a3925d7de
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:279743
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:123059
repl_backlog_histlen:156685

m162p203:

127.0.0.1:6379> info replication
# Replication
role:slave
master_host:192.168.161.114
master_port:6379
master_link_status:up
master_last_io_seconds_ago:1
master_sync_in_progress:0
slave_read_repl_offset:290875
slave_repl_offset:290875
slave_priority:100
slave_read_only:1
replica_announced:1
connected_slaves:0
master_failover_state:no-failover
master_replid:00bad10aad1b2ddde89253fd5c026c9a3925d7de
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:290875
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:87690
repl_backlog_histlen:203186
127.0.0.1:6379> 

3.sentinel配置

现在对3个节点的sentinel进行配置。sentinel的配置文件在redis的安装目录中已经存在，只需要复制到制定的位置即可。
在/opt/redis-6.2.6目录中：

[root@m162p203 redis-6.2.6]# ll
total 244
-rw-rw-r--  1 root root 33624 Oct  4 18:59 00-RELEASENOTES
-rw-rw-r--  1 root root    51 Oct  4 18:59 BUGS
-rw-rw-r--  1 root root  5026 Oct  4 18:59 CONDUCT
-rw-rw-r--  1 root root  3384 Oct  4 18:59 CONTRIBUTING
-rw-rw-r--  1 root root  1487 Oct  4 18:59 COPYING
drwxrwxr-x  7 root root   213 Oct 26 11:18 deps
-rw-rw-r--  1 root root    11 Oct  4 18:59 INSTALL
-rw-rw-r--  1 root root   151 Oct  4 18:59 Makefile
-rw-rw-r--  1 root root  6888 Oct  4 18:59 MANIFESTO
-rw-rw-r--  1 root root 21567 Oct  4 18:59 README.md
-rw-rw-r--  1 root root 93724 Oct  4 18:59 redis.conf
-rwxrwxr-x  1 root root   275 Oct  4 18:59 runtest
-rwxrwxr-x  1 root root   279 Oct  4 18:59 runtest-cluster
-rwxrwxr-x  1 root root  1079 Oct  4 18:59 runtest-moduleapi
-rwxrwxr-x  1 root root   281 Oct  4 18:59 runtest-sentinel
-rw-rw-r--  1 root root 13768 Oct  4 18:59 sentinel.conf
drwxrwxr-x  3 root root 12288 Oct 26 11:20 src
drwxrwxr-x 11 root root   182 Oct  4 18:59 tests
-rw-rw-r--  1 root root  3055 Oct  4 18:59 TLS.md
drwxrwxr-x  9 root root  4096 Oct 26 11:22 utils

现在将sentinel.conf copy到/etc/redis目录：

cp /opt/redis-6.2.6/sentinel.conf  /etc/redis/sentinel_26379.conf

由于sentinel与redis实例是一一对应的关系，那么sentinel将使用26379端口。我们将配置文件也做如此命名，便于后续在同一个服务器配置多个redis和sentinel。

在三个节点中的sentinel配置如下：

#监听端口
port 26379
#设置daemonize为yes,否则不会采用守护进程启动，启动命令会阻塞
daemonize yes
# pidfile 加上端口
pidfile "/var/run/redis-sentinel_26379.pid"
#自定义logfile文件的位置
logfile "/opt/redis/logs/sentinel_26379.log"
dir "/tmp"
#sentinel都指向redis集群的主节点
sentinel monitor mymaster 192.168.161.144 6379 2

acllog-max-len 128
sentinel deny-scripts-reconfig yes
sentinel resolve-hostnames no

protected-mode no
user default on nopass ~* &* +@all
sentinel myid 231bd2b57f330458efb37dd895b0b9cdac98c145
sentinel config-epoch mymaster 0
sentinel leader-epoch mymaster 0
sentinel current-epoch 0

在三个节点m161p114、m161p115、m162p203三个服务中，sentinel的配置都相同。
在sentinel启动的时候，都指向reids的master节点。

之后启动sentinel。
m161p114:

[root@m161p114 redis]# cd /etc/redis
[root@m161p114 redis]# redis-sentinel sentinel_26379.conf 

m161p115:

[root@m161p115 redis]# cd /etc/redis
[root@m161p115 redis]# redis-sentinel sentinel_26379.conf 

m162p203:

[root@m162p203 redis]# cd /etc/redis
[root@m162p203 redis]# redis-sentinel sentinel_26379.conf 

sentinel也支持redis的协议，可以通过redis-cli连接，并查看setinel的信息：
m161p114:

[root@m161p114 ~]# redis-cli -h 192.168.161.114 -p 26379
192.168.161.114:26379> info sentinel
# Sentinel
sentinel_masters:1
sentinel_tilt:0
sentinel_running_scripts:0
sentinel_scripts_queue_length:0
sentinel_simulate_failure_flags:0
master0:name=mymaster,status=ok,address=192.168.161.114:6379,slaves=2,sentinels=3
192.168.161.114:26379> 

m161p115:

[root@m161p115 redis]# redis-cli -h 192.168.161.115 -p 26379
192.168.161.115:26379> info sentinel
# Sentinel
sentinel_masters:1
sentinel_tilt:0
sentinel_running_scripts:0
sentinel_scripts_queue_length:0
sentinel_simulate_failure_flags:0
master0:name=mymaster,status=ok,address=192.168.161.114:6379,slaves=2,sentinels=3

m162p203:

192.168.162.203:26379> info sentinel
# Sentinel
sentinel_masters:1
sentinel_tilt:0
sentinel_running_scripts:0
sentinel_scripts_queue_length:0
sentinel_simulate_failure_flags:0
master0:name=mymaster,status=ok,address=192.168.161.114:6379,slaves=2,sentinels=3
192.168.162.203:26379> 

三个节点的sentinel信息都一致，sentinel配置成功。
查看sentinel的日志：

15545:X 26