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。