MHA能够在10~30秒内实现自动故障检测和故障转移，适用于对高可用性，数据完整性要求较高的场合。要做到无缝切换，还需要依赖于VIP漂移。VIP漂移比较常用的方式为使用keepalived或者使用脚本直接实现。脚本方式无须安装及复杂配置，相对简单。本文描述了基于脚本实现VIP切换。
对于keepalived的相关配置可以参考：CentOS 5.9下安装配置keepalived
1、当前主机环境及MHA配置
[root@vdbsrv1 ~]# more /etc/hosts
127.0.0.1 localhost.localdomain localhost
192.168.1.6 vdbsrv1 #master
192.168.1.7 vdbsrv2 #slave1
192.168.1.8 vdbsrv3 #slave2
192.168.1.12 vdbsrv4 #manager
###os环境
[root@vdbsrv4 ~]# more /etc/issue
CentOS release 5.9 (Final)
Kernel \r on an \m
###mysql环境
[root@vdbsrv4 ~]# mysql -e "show variables like 'version'"
+---------------+------------+
| Variable_name | Value |
+---------------+------------+
| version | 5.6.22-log |
+---------------+------------+
[root@vdbsrv4 ~]# masterha_manager --version
masterha_manager version 0.56.
###MHA配置信息
[root@vdbsrv4 ~]$ more /etc/masterha/app1.cnf
[server default]
manager_workdir=/var/log/masterha/app1
manager_log=/var/log/masterha/app1/manager.log
user=mha
password=xxx
ssh_user=root
repl_user=repl
repl_password=repl
ping_interval=1
shutdown_script=""
master_ip_online_change_script=""
report_script=""
master_ip_failover_script=/tmp/master_ip_failover
[server1]
hostname=vdbsrv1
master_binlog_dir=/data/mysqldata
[server2]
hostname=vdbsrv2
master_binlog_dir=/data/mysqldata
[server3]
hostname=vdbsrv3
master_binlog_dir=/data/mysqldata/
#candidate_master=1
2、测试VIP切换
###测试VIP(192.168.1.13)是否被启用
[root@vdbsrv4 ~]# ping 192.168.1.13
PING 192.168.1.13 (192.168.1.13) 56(84) bytes of data.
From 192.168.1.12 icmp_seq=10 Destination Host Unreachable
###为主机vdbsrv1添加VIP
[root@vdbsrv4 ~]# ssh vdbsrv1 "/sbin/ifconfig eth0:0 192.168.1.13 netmask 255.255.255.0 up"
###校验VIP是否成功启用
[root@vdbsrv4 ~]# ping 192.168.1.13
PING 192.168.1.13 (192.168.1.13) 56(84) bytes of data.
64 bytes from 192.168.1.13: icmp_seq=1 ttl=64 time=1.82 ms
###开启MHA
[root@vdbsrv4 ~]# masterha_manager --conf=/etc/masterha/app1.cnf &
###模拟主库宕机
[root@vdbsrv4 ~]# ssh vdbsrv1 "killall -r mysqld"
###查看管理节点日志，可以看到VIP已经漂移
[root@vdbsrv4 ~]# grep VIP /var/log/masterha/app1/manager.log
Disabling the VIP on old master: vdbsrv1
Enabling the VIP - 192.168.1.13/24 on the new master - vdbsrv2
###验证VIP是否位于节点vdbsrv2
[root@vdbsrv4 ~]# ssh vdbsrv2 "ifconfig |grep 1.13 -B1"
eth0:0 Link encap:Ethernet HWaddr 00:0C:29:5F:B2:EB
inet addr:192.168.1.13 Bcast:192.168.1.255 Mask:255.255.255.0
######查看管理节点MHA切换日志
[root@vdbsrv4 ~]# tail /var/log/masterha/app1/manager.log
Invalidated master IP address on vdbsrv1(192.168.1.6:3306)
The latest slave vdbsrv2(192.168.1.7:3306) has all relay logs for recovery.
Selected vdbsrv2(192.168.1.7:3306) as a new master.
vdbsrv2(192.168.1.7:3306): OK: Applying all logs succeeded.
vdbsrv2(192.168.1.7:3306): OK: Activated master IP address.
vdbsrv3(192.168.1.8:3306): This host has the latest relay log events.
Generating relay diff files from the latest slave succeeded.
vdbsrv3(192.168.1.8:3306): OK: Applying all logs succeeded. Slave started, replicating from vdbsrv2(192.168.1.7:3306)
vdbsrv2(192.168.1.7:3306): Resetting slave info succeeded.
Master failover to vdbsrv2(192.168.1.7:3306) completed successfully.
3、VIP切换perl脚本
[root@vdbsrv4 app1]# more /tmp/master_ip_failover
#!/usr/bin/env perl
use strict;
use warnings FATAL => 'all';
use Getopt::Long;
my (
$command, $ssh_user, $orig_master_host, $orig_master_ip,
$orig_master_port, $new_master_host, $new_master_ip, $new_master_port
);
my $vip = '192.168.1.13/24';
my $key = '0';
my $ssh_start_vip = "/sbin/ifconfig eth0:$key $vip";
my $ssh_stop_vip = "/sbin/ifconfig eth0:$key down";
GetOptions(
'command=s' => \$command,
'ssh_user=s' => \$ssh_user,
'orig_master_host=s' => \$orig_master_host,
'orig_master_ip=s' => \$orig_master_ip,
'orig_master_port=i' => \$orig_master_port,
'new_master_host=s' => \$new_master_host,
'new_master_ip=s' => \$new_master_ip,
'new_master_port=i' => \$new_master_port,
);
exit &main();
sub main {
print "\n\nIN SCRIPT TEST====$ssh_stop_vip==$ssh_start_vip===\n\n";
if ( $command eq "stop" || $command eq "stopssh" ) {
my $exit_code = 1;
eval {
print "Disabling the VIP on old master: $orig_master_host \n";
&stop_vip();
$exit_code = 0;
};
if ($@) {
warn "Got Error: $@\n";
exit $exit_code;
}
exit $exit_code;
}
elsif ( $command eq "start" ) {
my $exit_code = 10;
eval {
print "Enabling the VIP - $vip on the new master - $new_master_host \n";
&start_vip();
$exit_code = 0;
};
if ($@) {
warn $@;
exit $exit_code;
}
exit $exit_code;
}
elsif ( $command eq "status" ) {
print "Checking the Status of the script.. OK \n";
exit 0;
}
else {
&usage();
exit 1;
}
}
sub start_vip() {
`ssh $ssh_user\@$new_master_host \" $ssh_start_vip \"`;
}
sub stop_vip() {
return 0 unless ($ssh_user);
`ssh $ssh_user\@$orig_master_host \" $ssh_stop_vip \"`;
}
sub usage {
print
"Usage: master_ip_failover --command=start|stop|stopssh|status --orig_master_host=host --orig_master_ip=ip
--orig_master_port=port --new_master_host=host --new_master_ip=ip --new_master_port=port\n";
}