Keepalived+MySQL主主数据同步实现数据库高可用（HA）

原文链接：http://blog.csdn.net/xyang81/article/details/52659123

环境

操作系统版本：CentOS7 64位
MySQL版本：5.6.33
Keepalived版本：v1.2.23
节点1IP：192.168.1.205 主机名：edu-mysql-01
节点2IP：192.168.1.206 主机名：edu-mysql-02
VIP（虚拟IP）：192.168.1.207

下文中说到和vip即指192.168.1.207，节点1或205即指192.168.1.205，节点2或206即指192.168.1.206

MySQL高可用主要是通过Keepalived这款软件来实现多个节点的服务可用性检测和故障转移，对外提供VIP地址供客户端连接，由keepalived根据服务的状态，负责将vip漂移到真实可用的机器上，从而实现服务的高可用。阅读本文前，需要先安装MySQL、Keepalived以及MySQL主主同步配置，可参考我之前写的文章自行安装与配置：
1>、《 MySQL5.7安装与配置（YUM）》
2>、《MySQL主主数据同步》
3>、《Keepalived安装与配置》

本文配置keepalived为非抢占模式。

节点1配置

shell> vi /etc/keepalived/keepalived.conf
! Configuration File for keepalived

global_defs {
   router_id db-01
}

vrrp_instance VI_1 {
    state BACKUP # 两个节点都为BACKUP状态，根据优先级大小判断谁为MASTER
    interface enp0s3
    virtual_router_id 51
    priority 100
    advert_int 1
    nopreempt # 非抢占模式
    authentication {
        auth_type PASS
        auth_pass 1111
    }

    # 虚拟IP池
    virtual_ipaddress {
        192.168.1.207
    }
}

virtual_server 192.168.1.207 3306 {
     delay_loop 2
     lb_algo wrr
     lb_kind DR
     persistence_timeout 60
     protocol TCP
     real_server 192.168.1.205 3306 {
         weight 3
         notify_down /etc/keepalived/mysql.sh  # 当mysql服务down了之后，执行的脚本
         TCP_CHECK {
             connect_timeout 10   # mysql连接超时时长（秒）
             nb_get_retry 3       # mysql服务连接失败，重试次数
             delay_before_retry 3 #每隔3秒检测一次mysql服务是否可用
             connect_port 3306
         }
     }
}

/etc/keepalived/mysql.sh配置：

#!/bin/sh
pkill keepalived

当mysql服务停止时，会执行/etc/keepalived/mysql.sh脚本，将当前节点的keepalived服务停止，这样vip就会切换到另外一个节点上，从而实现了服务的高可用。

节点2配置

shell> vi /etc/keepalived/keepalived.conf
! Configuration File for keepalived

global_defs {
   router_id db-02
}

vrrp_instance VI_1 {
    state BACKUP
    interface enp0s3
    virtual_router_id 51
    priority 90
    advert_int 1
    nopreempt
    authentication {
        auth_type PASS
        auth_pass 1111
    }

    virtual_ipaddress {
        192.168.1.207
    }
}

virtual_server 192.168.1.207 3306 {
     delay_loop 2
     lb_algo wrr
     lb_kind DR
     persistence_timeout 60
     protocol TCP
     real_server 192.168.1.206 3306 {
         weight 3
         notify_down /etc/keepalived/mysql.sh
         TCP_CHECK {
             connect_timeout 10
             nb_get_retry 3
             delay_before_retry 3
             connect_port 3306
         }
     }
}

/etc/keepalived/mysql.sh配置同节点1

启动MySQL和Keepalived服务

shell> service mysql start
shell> service keepalived start

注意：先启动mysql，再启动keepalived。因为keepalived启动之后会去连接mysql，检测服务是否可用，如果3次都没连接成功，则会将keepalived进程杀死。

连接测试

注意：连接到VIP地址，而非直接连接到真实的MySQL服务器。

先看看vip漂在哪台服务器上：

从上图得知，此时VIP漂移在节点1（192.168.1.205）上。

shell> mysql -u root -proot -h 192.168.1.207

注：在指定ip连接到mysql时，需要授权配置远程连接的帐号、密码和ip。如：grant all privileges on *.* to 'root'@'%' identified by 'root' with grant option;

故障转移测试

从上面连接测试得知，此时vip漂移在192.168.1.205节点上，所以通过vip（192.168.1.207）连接到的真实服务器是192.168.1.205。将205的mysql服务停止，观察vip是否会切换到206上。

通过/var/log/message文件可以看到keepalived故障的日志

节点1的日志：

Sep 25 16:00:32 edu-mysql-01 Keepalived_healthcheckers[3517]: TCP connection to [192.168.1.205]:3306 failed.
Sep 25 16:00:35 edu-mysql-01 Keepalived_healthcheckers[3517]: TCP connection to [192.168.1.205]:3306 failed.
Sep 25 16:00:35 edu-mysql-01 Keepalived_healthcheckers[3517]: Check on service [192.168.1.205]:3306 failed after 1 retry.
Sep 25 16:00:35 edu-mysql-01 Keepalived_healthcheckers[3517]: Removing service [192.168.1.205]:3306 from VS [192.168.1.207]:3306
Sep 25 16:00:35 edu-mysql-01 Keepalived_healthcheckers[3517]: Executing [/etc/keepalived/mysql.sh] for service [192.168.1.205]:3306 in VS [192.168.1.207]:3306
Sep 25 16:00:35 edu-mysql-01 Keepalived_healthcheckers[3517]: Lost quorum 1-0=1 > 0 for VS [192.168.1.207]:3306
Sep 25 16:00:35 edu-mysql-01 kernel: IPVS: __ip_vs_del_service: enter
Sep 25 16:00:35 edu-mysql-01 Keepalived[3515]: Stopping
Sep 25 16:00:35 edu-mysql-01 Keepalived_healthcheckers[3517]: Stopped
Sep 25 16:00:35 edu-mysql-01 Keepalived_vrrp[3518]: VRRP_Instance(VI_1) sent 0 priority
Sep 25 16:00:35 edu-mysql-01 Keepalived_vrrp[3518]: VRRP_Instance(VI_1) removing protocol VIPs.
Sep 25 16:00:36 edu-mysql-01 Keepalived_vrrp[3518]: Stopped
Sep 25 16:00:36 edu-mysql-01 Keepalived[3515]: Stopped Keepalived v1.2.23 (09/12,2016)

前三行是keepalived心跳检测，每秒检测一次mysql服务是否可用，当第3次连接失败时，将该服务从lvs真实服务器列表中移除（第4行），并执行/etc/keepalived/mysql.sh脚本（第5行）停止keepalived服务，转让vip使用权。

节点2的日志：

Sep 25 16:00:36 edu-mysql-02 Keepalived_vrrp[3457]: VRRP_Instance(VI_1) Transition to MASTER STATE
Sep 25 16:00:37 edu-mysql-02 Keepalived_vrrp[3457]: VRRP_Instance(VI_1) Entering MASTER STATE
Sep 25 16:00:37 edu-mysql-02 Keepalived_vrrp[3457]: VRRP_Instance(VI_1) setting protocol VIPs.
Sep 25 16:00:37 edu-mysql-02 Keepalived_vrrp[3457]: Sending gratuitous ARP on enp0s3 for 192.168.1.207
Sep 25 16:00:37 edu-mysql-02 Keepalived_vrrp[3457]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on enp0s3 for 192.168.1.207
Sep 25 16:00:37 edu-mysql-02 Keepalived_vrrp[3457]: Sending gratuitous ARP on enp0s3 for 192.168.1.207
Sep 25 16:00:37 edu-mysql-02 Keepalived_vrrp[3457]: Sending gratuitous ARP on enp0s3 for 192.168.1.207
Sep 25 16:00:37 edu-mysql-02 Keepalived_vrrp[3457]: Sending gratuitous ARP on enp0s3 for 192.168.1.207
Sep 25 16:00:37 edu-mysql-02 Keepalived_vrrp[3457]: Sending gratuitous ARP on enp0s3 for 192.168.1.207
Sep 25 16:00:37 edu-mysql-02 Keepalived_healthcheckers[3456]: Netlink reflector reports IP 192.168.1.207 added
Sep 25 16:00:42 edu-mysql-02 Keepalived_vrrp[3457]: Sending gratuitous ARP on enp0s3 for 192.168.1.207
Sep 25 16:00:42 edu-mysql-02 Keepalived_vrrp[3457]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on enp0s3 for 192.168.1.207

节点2当前是BACKUP状态，当收到节点1挂掉的通知后，将自己的状态转换为master状态（第1行），接着将vip（192.168.1.207）绑定到enp0s3网卡上（第3到第5行）。

查看故障转移后的vip

从上图可知，vip成功从205转移到了206上。

此时在之前已经和vip建立了连接的mysql客户端当中，再执行sql时，第一次会执行失败，因为之前的连接已经断开，第二次执行时，会尝试重新连接到vip对应的新的mysql真实服务器上。如下图所示：