文章结构如下：

1、MHA简介
  Master high availability manager and tools for MySQL,是日本的一位MySQL专家采用perl语言编写的一个脚本管理工具，该工具进适用于msql replication环境。目的在于维持master主库的高可用性，MHA是自动的master故障转移和slave提升的软件包，基于标准的MYSQL复制（异步/半同步）。
下载地址：
https://github.com/yoshinorim/mha4mysql-manager/releases
https://github.com/yoshinorim/mha4mysql-node/releases
其他需要下载的包地址：
http://rpm.pbone.net/index.php3?stat=3&limit=5&srodzaj=1&dl=40&search=perl-Module-Install&field=

2、MHA原理
  MHA的目的在于维持MYSQL Replication 中master库的高可用性，其最大特点是可以修复多个slave之间的差异日志，最终使所有slave保持一致，然后从中选择一个充当新的master,并将其他slave指向它。当master出现故障时，可以通过对比slave之间的I/O thread读取主库binlog的position号，选取最接近的slave 作为备选主库，其他的从库可以通过与备库主库对比生成差异的中继日志，在备选主库上应用从原来master保存的binlog,同时将备选主库提升为master，最后在其他slave上应用相应的差异中继日志并从新的master开始复制。

3、MHA优缺点
优点
1、故障切换时，可以自行判断从哪个库与主库的数据最接近，然后切换到上面，可以减少数据的丢失，保证数据的一致性。
2、支持binlog server，可以提高binlog的传送效率，进一步减少数据丢失的风险。
3、结合MYSQL 5.7的增强半同步功能，确保故障切换时数据不丢失。
缺点
1、自动切换的脚本太简单了，而且比较老化，建议后期逐渐完善
2、搭建,MHA架构需要开启LINUX系统互信协议，所以对于系统安全性来说是个不小的考验。

4、MHA工具包的功能
1、Manager管理工具
masterha_check_ssh：检查MHA的ssh配置。
masterha_check_repl:检查MYSQL数据库的主从复制功能。
masterha_manager：启动MHA服务。
masterha_check_status：检查当前MHA运行状态。
masterha_master_monitor：监测Master是否宕机。
masterha_master_switch：控制故障转移（手动或者自动）。
masterha_conf_host：添加或删除配置的server信息。
2、Node数据节点工具
save_binary_logs：保存和复制master的二进制日志。
apply_diff_relay_logs：识别差异的中继日志时间并应用于其他slave。
filter_mysqlbinlog:去除不必要的rollback事件（MHA已不再使用这个工具）。
purge_relay_logs：清除中继日志（不会阻塞SQL线程）。

5、MySQL MHA安装以及演练

5.1 配置互信
配置三台机器的互信：
cd /root/.ssh/
ssh-keygen -t dsa -P '' -f id_dsa
cat id_dsa.pub >> authorized_keys
从库1执行：
ssh-keygen -t dsa -P '' -f id_dsa
cat id_dsa.pub >> authorized_keys
从库2执行：
ssh-keygen -t dsa -P '' -f id_dsa
cat id_dsa.pub >> authorized_keys
在把秘钥的传到主库过程：
scp /root/.ssh/id_dsa.pub 172.16.10.22:/root/.ssh/id_dsa.pub.61
scp /root/.ssh/id_dsa.pub 172.16.10.22:/root/.ssh/id_dsa.pub.62
查看主库秘钥：
接收完成后执行合并秘钥：
cat id_dsa.pub.61 >> authorized_keys
cat id_dsa.pub.62 >> authorized_keys
scp /root/.ssh/authorized_keys 172.16.10.61:/root/.ssh/
scp /root/.ssh/authorized_keys 172.16.10.62:/root/.ssh/
然后三台服务器添加域名解析：
vim /etc/hosts
172.16.10.22 rac2
172.16.10.61 racdg1
172.16.10.62 racdg2
验证互信：
主执行：
ssh racdg1 date
ssh racdg2 date
Slave1执行：
ssh rac2 date
ssh racdg2 date
Slave2执行：
ssh rac2 date
ssh racdg1 date

5.2 搭建一主两从
搭建主从环境，使用的是5.7版本，基于GTID+ROW模式进行搭建。
所以机器执行创建复制账号步骤：
create user repl@'172.16.10.%' identified by 'mysql';
grant replication slave,replication client on *.* to repl@'172.16.10.%';
flush privileges;
show grants for repl@'172.16.10.%';
所有主机创建管理账号：
create user admin@'172.16.10.%' identified by 'mysql';
grant all privileges on *.* to admin@'172.16.10.%';
flush privileges;
配置主从命令并且开启主从同步：
初始化：
/usr/local/mysql/bin/mysqldump -S /tmp/mysql.sock --single-transaction -uroot -pmysql --master-data=2 -A > slave.sql
注意：必须加参数 –master-data=2,让备份出来的文件中记录备份这一刻binlog文件与position号，为搭建主从环境做准备。查看备份文件中记录的当前binlog文件和position号。
scp slave.sql 172.16.10.61:/root
scp slave.sql 172.16.10.62:/root
注意，如果主从GTID不一样，数据一致可以：
set global gtid_purged='*******';
主库需要以下配置：
gtid_mode=on
enforce_gtid_consistency=on
log_bin=on
从库需要以下配置：
servier-id主从库不能一样。
gtid_mode=on
enforce_gtid_consistency=on
log_slave_updates=1
mysql -S /tmp/mysql.sock -uroot -pmysql < slave.sql
从库执行：
change master to master_host='172.16.10.22',master_port=3307,master_user='repl',master_password='mysql',master_auto_position=1;
start slave;
show slave status\G;

5.3 安装MHA节点
所有MHA服务器安装Perl环境
yum -y install perl-DBD-MySQL
注意最新的为0.58版本，但是对应的是centos7/redhat7,如果是低版本，建议用0.57（本人已经踩过这个坑）
a) 安装MHA-NODE节点
所有节点上执行以下：
tar -zxvf mha4mysql-node-0.57.tar.gz
yum -y install perl-CPAN*
cd mha4mysql-node-0.57
perl Makefile.PL
make && make install
ll -h /usr/local/bin/

b) 安装配置MHA-manager管理节点
在Salve2执行以下操作：
安装管理节点，先安装介质包：
yum -y install perl-DBD-MySQL perl-Config-Tiny perl-Log-Dispatch perl-Parallel-ForkManager perl-Time-HiRes
yum -y install perl*
查看，并下载需要安装的依赖包：
先检查：
rpm -qa|grep perl-Config-Tiny
rpm -qa|grep perl-Email-Date-Format
rpm -qa|grep perl-Log-Dispatch
rpm -qa|grep perl-Mail-Sender
rpm -qa|grep perl-Mail-Sendmail
rpm -qa|grep perl-MIME-Lite
rpm -qa|grep perl-Time-HiRes
rpm -qa|grep perl-Parallel-ForkManager
后安装：
rpm -ivh perl-Config-Tiny-2.12-1.el6.rfx.noarch.rpm
rpm -ivh perl-Email-Date-Format-1.002-1.el6.rfx.noarch.rpm
rpm -ivh perl-Parallel-ForkManager-0.7.9-1.el6.noarch.rpm
rpm -ivh perl-Mail-Sendmail-0.79_16-4.2.noarch.rpm
rpm -ivh perl-Mail-Sender-0.8.16-3.el6.noarch.rpm
rpm -ivh perl-MIME-Lite-3.029-1.el6.rfx.noarch.rpm
rpm -ivh perl-Parallel-ForkManager-0.7.9-1.el6.noarch.rpm
rpm -ivh perl-Log-Dispatch-2.27-1.el6.noarch.rpm

安装管理节点：
tar -zxvf mha4mysql-manager-0.57.tar.gz
cd mha4mysql-manager-0.57
perl Makefile.PL
make && make install
ll -h /usr/local/bin

进行管理节点MHA的配置过程

Slave2执行：
mkdir -p /usr/local/mha
mkdir -p /etc/mha
vim /etc/mha/mha.conf
[server default]
user=admin
password=mysql
manager_workdir=/usr/local/mha
manager_log=/usr/local/mha/manager.log
remote_workdir=/usr/local/mha
ssh_user=root
repl_user=repl
repl_password=mysql
ping_interval=1
master_ip_failover_script=/usr/local/scripts/master_ip_failover
master_ip_online_change_script=/usr/local/scripts/master_ip_online_change

[server1]
hostname=172.16.10.22
ssh_port=22
master_binlog_dir=/data/mysql/logs
candidate_master=1
port=3306

[server2]
hostname=172.16.10.61
ssh_port=22
master_binlog_dir=/data/mysql/logs
candidate_master=1
port=3306

[server3]
hostname=172.16.10.62
ssh_port=22
master_binlog_dir=/data/mysql/logs
no_master=1
port=3306
注释：
manager_workdir=/usr/local/mha //设置manager的工作目录manager_log=/usr/local/mhamanager.log //设置manager的日志
ping_interval=1 //设置监控主库，发送ping包的时间间隔，默认是3秒，尝试三次没有回应的时候自动进行failover
master_ip_failover_script=/usr/local/scripts/master_ip_failover //设置自动failover时候的切换脚本
master_ip_online_change_script=/usr/local/scripts/master_ip_online_change //设置手动切换时候的切换脚本
candidate_master=1 //设置为候选master，如果设置该参数以后，发生主从切换以后将会将此从库提升为主库，即使这个主库不是集群中事件最新的slave
check_repl_delay=0 //默认情况下如果一个slave落后master 100M的relay logs的话，MHA将不会选择该slave作为一个新的master，因为对于这个slave的恢复需要花费很长时间，通过设置check_repl_delay=0,MHA触发切换在选择一个新的master的时候将会忽略复制延时，这个参数对于设置了candidate_master=1的主机非常有用，因为这个候选主在切换的过程中一定是新的master
no_master=1 //意味着这个server从来不会成为新的master,这个参数用来标记从来不用成为新主的服务器。

编辑failover切换脚本：
mkdir -p /usr/local/scripts
vim /usr/local/scripts/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 = '172.16.10.30/24';
my $key = '1';
#my $ssh_start_vip = "/sbin/ip addr add $vip dev eth0";
my $ssh_start_vip = "/sbin/ifconfig eth0:$key $vip";
#my $ssh_stop_vip = "/sbin/ifconfig eth0:$key down";
my $ssh_stop_vip = "/sbin/ip addr del $vip dev eth0";

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";
}
chmod +x /usr/local/scripts/master_ip_failover

vim /usr/local/scripts/master_ip_online_change
#!/usr/bin/env perl
# Copyright (C) 2011 DeNA Co.,Ltd.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
## Note: This is a sample script and is not complete. Modify the script based on your environment.
use strict;
use warnings FATAL => 'all';
use Getopt::Long;
use MHA::DBHelper;
use MHA::NodeUtil;
use Time::HiRes qw( sleep gettimeofday tv_interval );
use Data::Dumper;
my $_tstart;
my $_running_interval = 0.1;
my $vip = '172.16.10.30';
my $key = "2";
my $ssh_start_vip = "/sbin/ifconfig eth0:$key $vip";
my $ssh_stop_vip = "/sbin/ip addr del $vip dev eth0";
my $ssh_send_garp = "/sbin/arping -U $vip -I eth0 -c 1";
my (
$command, $orig_master_is_new_slave, $orig_master_host,
$orig_master_ip, $orig_master_port, $orig_master_user,
$orig_master_password, $orig_master_ssh_user, $new_master_host,
$new_master_ip, $new_master_port, $new_master_user,
$new_master_password, $new_master_ssh_user,
);
GetOptions(
'command=s' => \$command,
'orig_master_is_new_slave' => \$orig_master_is_new_slave,
'orig_master_host=s' => \$orig_master_host,
'orig_master_ip=s' => \$orig_master_ip,
'orig_master_port=i' => \$orig_master_port,
'orig_master_user=s' => \$orig_master_user,
'orig_master_password=s' => \$orig_master_password,
'orig_master_ssh_user=s' => \$orig_master_ssh_user,
'new_master_host=s' => \$new_master_host,
'new_master_ip=s' => \$new_master_ip,
'new_master_port=i' => \$new_master_port,
'new_master_user=s' => \$new_master_user,
'new_master_password=s' => \$new_master_password,
'new_master_ssh_user=s' => \$new_master_ssh_user,
);
exit &main();
sub start_vip(){
`ssh $new_master_ssh_user\@$new_master_host \" $ssh_start_vip \"`;
`ssh $new_master_ssh_user\@$new_master_host \" $ssh_send_garp \"`;
}
sub stop_vip(){
`ssh $orig_master_ssh_user\@$orig_master_host \" $ssh_stop_vip \"`;
}
sub current_time_us {
my ( $sec, $microsec ) = gettimeofday();
my $curdate = localtime($sec);
return $curdate . " " . sprintf( "%06d", $microsec );
}
sub sleep_until {
my $elapsed = tv_interval($_tstart);
if ( $_running_interval > $elapsed ) {
sleep( $_running_interval - $elapsed );
}
}
sub get_threads_util {
my $dbh = shift;
my $my_connection_id = shift;
my $running_time_threshold = shift;
my $type = shift;
$running_time_threshold = 0 unless ($running_time_threshold);
$type = 0 unless ($type);
my @threads;
my $sth = $dbh->prepare("SHOW PROCESSLIST");
$sth->execute();
while ( my $ref = $sth->fetchrow_hashref() ) {
my $id = $ref->{Id};
my $user = $ref->{User};
my $host = $ref->{Host};
my $command = $ref->{Command};
my $state = $ref->{State};
my $query_time = $ref->{Time};
my $info = $ref->{Info};
$info =~ s/^\s*(.*?)\s*$/$1/ if defined($info);
next if ( $my_connection_id == $id );
next if ( defined($query_time) && $query_time < $running_time_threshold );
next if ( defined($command) && $command eq "Binlog Dump" );
next if ( defined($user) && $user eq "system user" );
next
if ( defined($command)
&& $command eq "Sleep"
&& defined($query_time)
&& $query_time >= 1 );
if ( $type >= 1 ) {
next if ( defined($command) && $command eq "Sleep" );
next if ( defined($command) && $command eq "Connect" );
}
if ( $type >= 2 ) {
next if ( defined($info) && $info =~ m/^select/i );
next if ( defined($info) && $info =~ m/^show/i );
}
push @threads, $ref;
}
return @threads;
}
sub main {
if ( $command eq "stop" ) {
## Gracefully killing connections on the current master
# 1. Set read_only= 1 on the new master
# 2. DROP USER so that no app user can establish new connections
# 3. Set read_only= 1 on the current master
# 4. Kill current queries
# * Any database access failure will result in script die.
my $exit_code = 1;
eval {
## Setting read_only=1 on the new master (to avoid accident)
my $new_master_handler = new MHA::DBHelper();
# args: hostname, port, user, password, raise_error(die_on_error)_or_not
$new_master_handler->connect( $new_master_ip, $new_master_port,
$new_master_user, $new_master_password, 1 );
print current_time_us() . " Set read_only on the new master.. ";
$new_master_handler->enable_read_only();
if ( $new_master_handler->is_read_only() ) {
print "ok.\n";
}
else {
die "Failed!\n";
}
$new_master_handler->disconnect();
# Connecting to the orig master, die if any database error happens
my $orig_master_handler = new MHA::DBHelper();
$orig_master_handler->connect( $orig_master_ip, $orig_master_port,
$orig_master_user, $orig_master_password, 1 );
## Drop application user so that nobody can connect. Disabling per-session binlog beforehand
$orig_master_handler->disable_log_bin_local();
# print current_time_us() . " Drpping app user on the orig master..\n";
#drop_app_user($orig_master_handler);
## Waiting for N * 100 milliseconds so that current connections can exit
my $time_until_read_only = 15;
$_tstart = [gettimeofday];
my @threads = get_threads_util( $orig_master_handler->{dbh},
$orig_master_handler->{connection_id} );
while ( $time_until_read_only > 0 && $#threads >= 0 ) {
if ( $time_until_read_only % 5 == 0 ) {
printf
"%s Waiting all running %d threads are disconnected.. (max %d milliseconds)\n",
current_time_us(), $#threads + 1, $time_until_read_only * 100;
if ( $#threads < 5 ) {
print Data::Dumper->new( [$_] )->Indent(0)->Terse(1)->Dump . "\n"
foreach (@threads);
}
}
sleep_until();
$_tstart = [gettimeofday];
$time_until_read_only--;
@threads = get_threads_util( $orig_master_handler->{dbh},
$orig_master_handler->{connection_id} );
}
## Setting read_only=1 on the current master so that nobody(except SUPER) can write
print current_time_us() . " Set read_only=1 on the orig master.. ";
$orig_master_handler->enable_read_only();
if ( $orig_master_handler->is_read_only() ) {
print "ok.\n";
}
else {
die "Failed!\n";
}
## Waiting for M * 100 milliseconds so that current update queries can complete
my $time_until_kill_threads = 5;
@threads = get_threads_util( $orig_master_handler->{dbh},
$orig_master_handler->{connection_id} );
while ( $time_until_kill_threads > 0 && $#threads >= 0 ) {
if ( $time_until_kill_threads % 5 == 0 ) {
printf
"%s Waiting all running %d queries are disconnected.. (max %d milliseconds)\n",
current_time_us(), $#threads + 1, $time_until_kill_threads * 100;
if ( $#threads < 5 ) {
print Data::Dumper->new( [$_] )->Indent(0)->Terse(1)->Dump . "\n"
foreach (@threads);
}
}
sleep_until();
$_tstart = [gettimeofday];
$time_until_kill_threads--;
@threads = get_threads_util( $orig_master_handler->{dbh},
$orig_master_handler->{connection_id} );
}
## Terminating all threads
print current_time_us() . " Killing all application threads..\n";
$orig_master_handler->kill_threads(@threads) if ( $#threads >= 0 );
print current_time_us() . " done.\n";
$orig_master_handler->enable_log_bin_local();
$orig_master_handler->disconnect();
## Droping the VIP
print "Disabling the VIP an old master: $orig_master_host \n";
&stop_vip();
## After finishing the script, MHA executes FLUSH TABLES WITH READ LOCK
$exit_code = 0;
};
if ($@) {
warn "Got Error: $@\n";
exit $exit_code;
}
exit $exit_code;
}
elsif ( $command eq "start" ) {
## Activating master ip on the new master
# 1. Create app user with write privileges
# 2. Moving backup script if needed
# 3. Register new master's ip to the catalog database
# We don't return error even though activating updatable accounts/ip failed so that we don't interrupt slaves' recovery.
# If exit code is 0 or 10, MHA does not abort
my $exit_code = 10;
eval {
my $new_master_handler = new MHA::DBHelper();
# args: hostname, port, user, password, raise_error_or_not
$new_master_handler->connect( $new_master_ip, $new_master_port,
$new_master_user, $new_master_password, 1 );
## Set read_only=0 on the new master
$new_master_handler->disable_log_bin_local();
print current_time_us() . " Set read_only=0 on the new master.\n";
$new_master_handler->disable_read_only();
## Creating an app user on the new master
#print current_time_us() . " Creating app user on the new master..\n";
# create_app_user($new_master_handler);
print "Enabling the VIP $vip on the new master: $new_master_host \n";
&start_vip();
$new_master_handler->enable_log_bin_local();
$new_master_handler->disconnect();
## Update master ip on the catalog database, etc
$exit_code = 0;
};
if ($@) {
warn "Got Error: $@\n";
exit $exit_code;
}
exit $exit_code;
}
elsif ( $command eq "status" ) {
# do nothing
exit 0;
}
else {
&usage();
exit 1;
}
}
sub usage {
print
"Usage: master_ip_online_change --command=start|stop|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";
die;
}
chmod +x /usr/local/scripts/master_ip_online_change

利用MHA工具检测SSH。
安装需要的环境包：
yum -y install perl-Time-HiRes
执行检测命令：
/usr/local/bin/masterha_check_ssh --conf=/etc/mha/mha.conf

结果全是OK代表着SSH检测成功。

检测整个主从结构：
/usr/local/bin/masterha_check_repl --conf=/etc/mha/mha.conf
这个容易报错：
注意：update mysql.user set host='%' where user='root'; （需要主从root互相登陆）

5.4 添加VIP
在主库（172.16.10.22）上执行添加VIP的过程（第一次手动添加）
ip addr add 172.16.10.30/24 dev eth0:1
ip addr show
删除的话：ip addr del 172.16.10.30/24 dev eth0

5.5 启动MHA服务
在管理节点（172.16.10.62）slave2上执行MHA的启动：
nohup /usr/local/bin/masterha_manager --conf=/etc/mha/mha.conf > /tmp/mha_manager.log < /dev/null 2>&1 &
注意：如果做过一次FAILOVER测试,启动MHA 建议如下启动：
nohup /usr/local/bin/masterha_manager --conf=/etc/mha/mha.conf --ignore_last_failover > /tmp/mha_manager.log < /dev/null 2>&1 &
验证启动成功命令并且查看显示状态：
/usr/local/bin/masterha_check_status --conf=/etc/mha/mha.conf

5.6 故障转移演练
模拟主库（172.16.10.22）宕机，即停止MySQL服务。
mysqladmin -S /tmp/mysql3307.sock -uroot -pmysql shutdown
原salve1自动获得VIP 172.16.10.30，如下图：
ip addr

即salve1转换成新的主库。

Slave2指向新的主库，如下图：

且管理节点即（172.16.10.62）上MHA进程自动停止，如下图：
ps -elf | grep -v grep | grep MHA
root 11998 5673 0 09:01 pts/1 00:00:00 grep MHA
/usr/local/bin/masterha_check_status --conf=/etc/mha/mha.conf

5.7 恢复原master
启动原master
mysqld_safe --defaults-file=/etc/my.cnf &
重新配置主从：
当然，数据要一致是前提（生产上数据不一致，要备份恢复），配置新主从如下：
即原master变成新的从库：
新一主两从结构如下：

change master to master_host='172.16.10.61',master_port=3307,master_user='repl',master_password='mysql',master_auto_position=1;
手动在线切换：
测试环境执行下面一句：
/usr/local/bin/masterha_master_switch --conf=/etc/mha/mha.conf --master_state=alive --new_master_host=172.16.10.22 --new_master_port=3306 --orig_master_is_new_slave --running_updates_limit=10000
注意：回切可以不用启动monitor进程。

中间提示输入YES.

原Salve1（现为master）需要switch
查看VIP
VIP漂过来。回切成功。
后成功后启动MHA：
nohup /usr/local/bin/masterha_manager --conf=/etc/mha/mha.conf --ignore_last_failover > /tmp/mha_manager.log < /dev/null 2>&1 &