Redis 高可用方案Keepalived

我会带着你远行 2022-08-05 13:24 279阅读 0赞

在redis3.0没有现世之前，为了提高redis的高可用性，通常的做法是采用HAProxy或Keepalived来实现故障自动转移，事实上如果是做Failover而非负载均衡的话，Keepalived的效率肯定是超过HAProxy的，所以下面我们采用Keepalived的方案。方案的架构图如下：

![Center][]

上图中使用多组Master-Slave构成redis集群服务，在master和slave中使用Keepalived实现故障自动转移，在客户端实现对数据的一致性哈希储存，轻松的实现水平扩展。当然在实际使用过程可以考虑一主多从的方式使用Keepalived实现故障自动转移，并实现读写分离。

如下介绍一下使用配置：

**一、环境配置**  
master：192.168.36.54  
slave：192.168.36.189  
VIP：192.168.36.100  
**二、设计思路**  
当Master与Slave均运作正常时, Master负责服务，Slave负责Standby；  
当Master挂掉，Slave正常时, Slave接管服务，同时关闭主从复制功能；  
当Master恢复正常，则从Slave同步数据，同步数据之后关闭主从复制功能，恢复Master身份，于此同时Slave等待Master同步数据完成之后，恢复Slave身份。  
然后依次循环。  
需要注意的是，这样做需要在Master与Slave上都开启本地化策略，否则在互相自动切换的过程中，未开启本地化的一方会将另一方的数据清空，造成数据完全丢失。  
**三、使用配置  
1.redis安装**，参考：[http://blog.csdn.net/zhu\_tianwei/article/details/44890579][http_blog.csdn.net_zhu_tianwei_article_details_44890579]  
**2.安装配置Keepalived(root)**  
1）安装  
yum -y install keepalived  
默认安装完成keepalived之后是没有配置文件的，因此我们需要手动创建。  
2）配置  
在主服务器上：

mkdir /etc/keepalived  
vi /etc/keepalived/keepalived.conf

vrrp_script chk_redis { 
                    script "/etc/keepalived/scripts/redis_check.sh"   ###监控脚本 
                    interval 2                                        ###监控时间 
    } 
    vrrp_instance VI_1 { 
            state MASTER                            ###设置为MASTER
            interface eth0                          ###监控网卡    
            virtual_router_id 50
            priority 100                            ###权重值
            authentication { 
                         auth_type PASS             ###加密 
                         auth_pass redis            ###密码 
            } 
            track_script { 
                    chk_redis                       ###执行上面定义的chk_redis
            } 
            virtual_ipaddress { 
                 192.168.36.100                        ###VIP 
            }
            notify_master /etc/keepalived/scripts/redis_master.sh
            notify_backup /etc/keepalived/scripts/redis_backup.sh
            notify_fault  /etc/keepalived/scripts/redis_fault.sh
            notify_stop   /etc/keepalived/scripts/redis_stop.sh 
    }

在从服务器上：  
mkdir /etc/keepalived  
vi /etc/keepalived/keepalived.conf

vrrp_script chk_redis { 
                    script "/etc/keepalived/scripts/redis_check.sh"   ###监控脚本 
                    interval 2                                        ###监控时间 
    } 
    vrrp_instance VI_1 { 
            state BACKUP                                ###设置为BACKUP 
            interface eth0                              ###监控网卡
            virtual_router_id 50 
            priority 99                                ###比MASTRE权重值低 
            authentication { 
                         auth_type PASS 
                         auth_pass redis                ###密码与MASTRE相同
            } 
            track_script { 
                    chk_redis                           ###执行上面定义的chk_redis
            } 
            virtual_ipaddress { 
                 192.168.36.100                       ###VIP 
            } 
            notify_master /etc/keepalived/scripts/redis_master.sh
            notify_backup /etc/keepalived/scripts/redis_backup.sh
            notify_fault  /etc/keepalived/scripts/redis_fault.sh
            notify_stop   /etc/keepalived/scripts/redis_stop.sh 
    }

3）创建监控脚本  
在Master和Slave上创建监控Redis的脚本  
$ mkdir /etc/keepalived/scripts  
$ vi /etc/keepalived/scripts/redis\_check.sh

#!/bin/bash
    
    ALIVE=`/home/slim/redis/bin/redis-cli -h 192.168.36.54 -p 6379 PING`
    if [ "$ALIVE" == "PONG" ]; then
      echo $ALIVE
      exit 0
    else
      echo $ALIVE
      exit 1
    fi

脚本中ip和端口为本机的redis服务地址，根据实际情况配置。  
编写以下负责运作的关键脚本：  
notify\_master /etc/keepalived/scripts/redis\_master.sh  
notify\_backup /etc/keepalived/scripts/redis\_backup.sh  
notify\_fault /etc/keepalived/scripts/redis\_fault.sh  
notify\_stop /etc/keepalived/scripts/redis\_stop.sh  
因为Keepalived在转换状态时会依照状态来呼叫：  
当进入Master状态时会呼叫notify\_master  
当进入Backup状态时会呼叫notify\_backup  
当发现异常情况时进入Fault状态呼叫notify\_fault  
当Keepalived程序终止时则呼叫notify\_stop  
首先，在Redis Master上创建notity\_master与notify\_backup脚本：  
$vi /etc/keepalived/scripts/redis\_master.sh

#!/bin/bash
    
    REDISCLI="/home/slim/redis/bin/redis-cli"
    LOGFILE="/var/log/keepalived-redis-state.log"
    
    echo "[master]" >> $LOGFILE
    date >> $LOGFILE
    echo "Being master...." >> $LOGFILE 2>&1
    
    echo "Run SLAVEOF cmd ..." >> $LOGFILE
    $REDISCLI SLAVEOF 192.168.36.189 6379 >> $LOGFILE  2>&1
    sleep 10 #延迟10秒以后待数据同步完成后再取消同步状态
    
    echo "Run SLAVEOF NO ONE cmd ..." >> $LOGFILE
    $REDISCLI SLAVEOF NO ONE >> $LOGFILE 2>&1

当获取到master通知时，先开启从角色状态从192.168.36.189同步数据，完成之后再关闭从角色状态。

$ vi /etc/keepalived/scripts/redis\_backup.sh

#!/bin/bash
    
    REDISCLI="/home/slim/redis/bin/redis-cli"
    LOGFILE="/var/log/keepalived-redis-state.log"
    
    echo "[backup]" >> $LOGFILE
    date >> $LOGFILE
    echo "Being slave...." >> $LOGFILE 2>&1
    
    sleep 15 #延迟15秒待数据被对方同步完成之后再切换主从角色
    echo "Run SLAVEOF cmd ..." >> $LOGFILE
    $REDISCLI SLAVEOF 192.168.36.189 6379 >> $LOGFILE  2>&1

当获取到slave通知时，等待数据同步完成，切换成从角色。  
在Redis Slave上创建notity\_master与notify\_backup脚本：

$ vi /etc/keepalived/scripts/redis\_master.sh

#!/bin/bash
    
    REDISCLI="/home/slim/redis/bin/redis-cli"
    LOGFILE="/var/log/keepalived-redis-state.log"
    
    echo "[master]" >> $LOGFILE
    date >> $LOGFILE
    echo "Being master...." >> $LOGFILE 2>&1
    
    echo "Run SLAVEOF cmd ..." >> $LOGFILE
    $REDISCLI SLAVEOF 192.168.36.54 6379 >> $LOGFILE  2>&1
    sleep 10 #延迟10秒以后待数据同步完成后再取消同步状态
    
    echo "Run SLAVEOF NO ONE cmd ..." >> $LOGFILE
    $REDISCLI SLAVEOF NO ONE >> $LOGFILE 2>&1

$ vi /etc/keepalived/scripts/redis\_backup.sh

然后在Master与Slave创建如下相同的脚本：

$ vi /etc/keepalived/scripts/redis\_fault.sh

#!/bin/bash
    
    LOGFILE=/var/log/keepalived-redis-state.log
    
    echo "[fault]" >> $LOGFILE
    date >> $LOGFILE

$ vi /etc/keepalived/scripts/redis\_stop.sh

#!/bin/bash
    
    LOGFILE=/var/log/keepalived-redis-state.log
    
    echo "[stop]" >> $LOGFILE
    date >> $LOGFILE

给脚本都加上可执行权限：  
$ chmod +x /etc/keepalived/scripts/\*.sh

**3.启动服务**

脚本创建完成以后，我们开始按照如下流程进行测试：  
1)启动Master上的Redis(slim)  
$./bin/redis-server conf/redis.conf ;tail -f logs/redis.log  
2)启动Slave上的Redis(slim)  
$./bin/redis-server conf/redis.conf ;tail -f logs/redis.log  
3)启动Master上的Keepalived(root)  
$/etc/init.d/keepalived start  
4)启动Slave上的Keepalived(root)  
$/etc/init.d/keepalived start  
  
**4.测试**

1)尝试通过VIP连接Redis:  
$ ./bin/redis-cli -h 192.168.36.100 -p 6379 INFO  
连接成功，Slave也连接上来了。  
role:master  
slave0:192.168.36.189,6379,online  
2)尝试插入一些数据：  
$ ./bin/redis-cli -h 192.168.36.100 -p 6379 SET Hello Redis  
OK  
从VIP读取数据  
$ ./bin/redis-cli -h 10.6.1.200 GET Hello  
“Redis”  
从Master读取数据  
$ ./bin/redis-cli -h 192.168.36.54 -p 6379 GET Hello  
“Redis”  
从Slave读取数据  
$ ./bin/redis-cli -h 192.168.36.189 -p 6379 GET Hello  
“Redis”  
**4.模拟故障**  
将Master上的Redis进程杀死：  
$killall -9 redis-server  
查看Master上的Keepalived日志  
$ tailf /var/log/keepalived-redis-state.log  
\[fault\]  
  
同时Slave上的日志显示：  
$ tailf /var/log/keepalived-redis-state.log  
\[master\]  
Being master….  
Run SLAVEOF cmd …  
OK  
Run SLAVEOF NO ONE cmd …  
OK  
  
然后我们可以发现，Slave已经接管服务，并且担任Master的角色了。  
$ redis-cli -h 192.168.36.100 -p 6379 INFO  
$ redis-cli -h 192.168.36.189 -p 6379 INFO  
role:master  
然后我们恢复Master的Redis进程(slim)  
$ ./bin/redis-server conf/redis.conf ;tail -f logs/redis.log  
查看Master上的Keepalived日志  
$ tailf /var/log/keepalived-redis-state.log  
\[master\]  
Being master….  
Run SLAVEOF cmd …  
OK  
Run SLAVEOF NO ONE cmd …  
OK  
同时Slave上的日志显示：  
$ tailf /var/log/keepalived-redis-state.log  
\[backup\]  
Being slave….  
Run SLAVEOF cmd …  
OK  
可以发现目前的Master已经再次恢复了Master的角色，故障切换以及自动恢复都成功了。大家可以测试一下再故障情况下添加数据，服务正常后，数据是否正常同步。

文章参考： [http://heylinux.com/archives/1942.html][http_heylinux.com_archives_1942.html]

[Center]: /images/20220805/e97bde111c7140f191777a9949135369.png
[http_blog.csdn.net_zhu_tianwei_article_details_44890579]: http://blog.csdn.net/zhu_tianwei/article/details/44890579
[http_heylinux.com_archives_1942.html]: http://heylinux.com/archives/1942.html