MySQL5.6基于MHA方式高可用搭建

master 10.205.22.185 #MHA node

slave1 10.205.22.186  #MHA node+MHA manager

slave2 10.205.22.187  #MHA node

三台服务器的MySQL已经搭建好主从架构，并互相配置好ssh免密码登录。

1.下载MHA，并安装MHA包的依赖软件

https://downloads.mariadb.com/MHA（或者 https://github.com/yotoobo/linux/tree/master/mha）
yum install perl-Config-Tiny perl-Log-Dispatch perl-Time-HiRes perl-Parallel-ForkManager

2.安装MHA软件包

rpm -ivh mha4mysql-node-0.56-0.el6.noarch #所有节点安装
rpm -ivh mha4mysql-manager-0.56-0.el6.noarch #186管理节点安装

3.创建用户mha管理的账号，在所有mysql服务器上都需要执行：

GRANT ALL PRIVILEGES ON *.* TO 'mha_rep'@'10.205.22.%' IDENTIFIED BY '123456';

如果是在slave服务器上安装的manager，则需要创建以本机hostname名连接的账号,不然masterha_check_repl测试通不过。
GRANT ALL PRIVILEGES ON *.* TO 'mha_rep'@'master(主机名)' IDENTIFIED BY '123456'

4.在MHA manager服务器添加配置文件/etc/masterha/app1.cnf（自定义），并创建相关目录和修改权限

[server default]
manager_workdir=/var/log/masterha/app1
manager_log=/var/log/masterha/app1/manager.log
secondary_check_script= masterha_secondary_check -s 10.205.22.185 -s 10.205.22.186 #实现多路由监测Master的可用性
master_ip_failover_script=/usr/local/scripts/master_ip_failover

user=mha_rep
password=123456

ssh_user=root
repl_user=repl
repl_password=password
ping_interval=1

[server1]
hostname=10.205.22.185
candidate_master=1
master_binlog_dir=/home/data/mysql/binlog

[server2]
hostname=10.205.22.186
candidate_master=1
master_binlog_dir=/home/data/mysql/binlog

[server3]
hostname=10.205.22.187
no_master=1
master_binlog_dir=/home/data/mysql/binlog

mkdir -p /home/data/mysql/binlog #创建相关目录
chown -R mysql.mysql /home/data/mysql/binglog #修改权限

5.编写自动切换VIP的脚本，/usr/local/scripts/master_ip_failover ，并加上可执行权限+x。

!/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 = '10.205.22.111/24'; # Virtual IP
my $gateway = '10.205.22.1'; #Gateway IP
my $interface = 'eth0';
my $key = "1";
my $ssh_start_vip = "/sbin/ifconfig $interface:$key $vip;/sbin/arping -I $interface -c 3 -s $vip $gateway >/dev/null 2>&1";
my $ssh_stop_vip = "/sbin/ifconfig $interface:$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 "

IN SCRIPT TEST====$ssh_stop_vip==$ssh_start_vip===

";
if ( $command eq "stop" || $command eq "stopssh" ) {
# $orig_master_host, $orig_master_ip, $orig_master_port are passed.
# If you manage master ip address at global catalog database,
# invalidate orig_master_ip here.
my $exit_code = 1;
eval {
print "Disabling the VIP on old master: $orig_master_host 
";
&stop_vip();
$exit_code = 0;
};
if ($@) {
warn "Got Error: $@
";
exit $exit_code;
}
exit $exit_code;
}
elsif ( $command eq "start" ) {
# all arguments are passed.
# If you manage master ip address at global catalog database,
# activate new_master_ip here.
# You can also grant write access (create user, set read_only=0, etc) here.
my $exit_code = 10;
eval {
print "Enabling the VIP - $vip on the new master - $new_master_host 
";
&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 
";
`ssh $ssh_user@$orig_master_host " $ssh_start_vip "`;
exit 0;
}
else {
&usage();
exit 1;
}
}
# A simple system call that enable the VIP on the new master
sub start_vip() {
`ssh $ssh_user@$new_master_host " $ssh_start_vip "`;
}
# A simple system call that disable the VIP on the old_master
sub stop_vip() {
`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
";
}

6.检查配置文件

利用mha工具检测ssh
masterha_check_ssh --conf=/etc/masterha_application.cnf

使用mha工具check检查repl环境
masterha_check_repl --conf=/etc/masterha_application.cnf

7.开启MHA manager，并查看状态

开启masterha_manager
nohup masterha_manager --conf=/etc/masterha/app1.cnf > /tmp/mha_manager.log  2>&1 &
（masterha_stop --conf=/etc/masterha/app1.cnf #关闭时使用的命令）

查看
masterha_check_status --conf=/etc/masterha/app1.cnf

8.模拟MySQL故障，查看VIP漂移和MySQL自动切换情况（切换后MHA服务会自动停止）

/etc/init.d/mysqld stop #master上操作
在manager上查看切换日志：tail -f /var/log/masterha/app1/manager.log 
查看备用节点情况：show master status G

9.MySQL故障服务器重新加入MHA环境

1.把故障服务器设为新的slave
2.重新启动MHA manager
3.查看MHA状态

10.在线手动切换主从，没有启用MHA自动切换功能

1.原master出现故障
masterha_stop --conf=/etc/masterha/app1.cnf #停止
masterha_master_switch --master_state=dead --conf=/etc/masterha/app1.cnf --dead_master_host=10.205.22.185 --dead_master_port=3306 --new_master_host=10.205.22.186 --new_master_port=3306 --ignore_last_failover

2.把原master变为slave切换
masterha_master_switch --conf=/etc/masterha/app1.cnf --master_state=alive --new_master_host=10.205.22.185 --new_master_port=3306 --orig_master_is_new_slave

为了保证数据完全一致性，在最快的时间内完成切换，MHA的在线切换必须满足以下条件才会切换成功，否则会切换失败。

1.所有slave的IO线程都在运行

2.所有slave的SQL线程都在运行

3.所有的show slave status的输出中Seconds_Behind_Master参数小于或者等于running_updates_limit秒，如果在切换过程中不指定running_updates_limit,那么默认情况下running_updates_limit为1秒。

4.在master端，通过show processlist输出，没有一个更新花费的时间大于running_updates_limit秒。