MHA（Master High Availability）目前在MySQL高可用方面是一个相对成熟的解决方案，它由日本DeNA公司youshimaton（现就职于Facebook公司）开发，是一套优秀的作为MySQL高可用性环境下故障切换和主从提升的高可用软件。在MySQL故障切换过程中，MHA能做到在0~30秒之内自动完成数据库的故障切换操作，并且在进行故障切换的过程中，MHA能在最大程度上保证数据的一致性，以达到真正意义上的高可用。
该软件由两部分组成：MHA Manager（管理节点）和MHA Node（数据节点）。MHA Manager可以单独部署在一台独立的机器上管理多个master-slave集群，也可以部署在一台slave节点上。MHA Node运行在每台MySQL服务器上，MHA Manager会定时探测集群中的master节点，当master出现故障时，它可以自动将最新数据的slave提升为新的master，然后将所有其他的slave重新指向新的master。整个故障转移过程对应用程序完全透明。
在MHA自动故障切换过程中，MHA试图从宕机的主服务器上保存二进制日志，最大程度的保证数据的不丢失，但这并不总是可行的。例如，如果主服务器硬件故障或无法通过ssh访问，MHA没法保存二进制日志，只进行故障转移而丢失了最新的数据。使用MySQL 5.5的半同步复制，可以大大降低数据丢失的风险。MHA可以与半同步复制结合起来。如果只有一个slave已经收到了最新的二进制日志，MHA可以将最新的二进制日志应用于其他所有的slave服务器上，因此可以保证所有节点的数据一致性。
目前MHA主要支持一主多从的架构，要搭建MHA,要求一个复制集群中必须最少有三台数据库服务器，一主二从，即一台充当master，一台充当备用master，另外一台充当从库，因为至少需要三台服务器。
Manager工具包主要包括以下几个工具：
masterha_check_ssh 检查MHA的SSH配置状况
masterha_check_repl 检查MySQL复制状况
masterha_manger 启动MHA
masterha_check_status 检测当前MHA运行状态
masterha_master_monitor 检测master是否宕机
masterha_master_switch 控制故障转移（自动或者手动）
masterha_conf_host 添加或删除配置的server信息
Node工具包（这些工具通常由MHA Manager的脚本触发，无需人为操作）主要包括以下几个工具：
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事件并将其差异的事件应用于其他的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）
角色 ip地址 主机名 server_id 类型
Master 192.168.165.135 MySQL-A 1 写入
Candicate master 192.168.165.136 MySQL-B 2 读
Monitor host /Slave 192.168.165.137 MySQL-C 3 读
建立MHA账号：
MariaDB [(none)]> grant all privileges on *.* to 'admin'@'%' identified by '123456';
创建主从复制账号：
MariaDB [(none)]> grant replication slave,replication client on *.* to 'repl'@'%' identified by 'repl';
安装依赖包：
rpm -ivh perl-Config-Tiny-2.12-7.1.el6.noarch.rpm
rpm -ivh perl-DBD-MySQL-4.013-3.el6.i686.rpm
rpm -ivh compat-db43-4.3.29-15.el6.x86_64.rpm
rpm -ivh perl-Mail-Sender-0.8.16-3.el6.noarch.rpm
rpm -ivh perl-Parallel-ForkManager-0.7.9-1.el6.noarch.rpm
rpm -ivh perl-TimeDate-1.16-11.1.el6.noarch.rpm
rpm -ivh perl-MIME-Types-1.28-2.el6.noarch.rpm
rpm -ivh perl-MailTools-2.04-4.el6.noarch.rpm
rpm -ivh perl-Email-Date-Format-1.002-5.el6.noarch.rpm
rpm -ivh perl-Params-Validate-0.92-3.el6.
rpm -ivh perl-Params-Validate-0.92-3.el6.x86_64.rpm
rpm -ivh perl-MIME-Lite-3.027-2.el6.noarch.rpm
rpm -ivh perl-Mail-Sendmail-0.79-12.el6.noarch.rpm
rpm -ivg perl-Log-Dispatch-2.27-1.el6.noarch.rpm
或安装epel源
在管理节点安装MHA管理和客户端安装包：
tar -zxvf mha4mysql-manager-0.56.tar.gz
cd mha4mysql-manager-0.56
perl Makefile.PL
make
make install tar -zxvf mha4mysql-node-0.56.tar.gz
cd mha4mysql-node-0.56
perl Makefile.PL
make
make install
将脚本拷贝到/usr/local/bin目录下面：
[root@mysql-C bin]# ll
total 40
-rwxr-xr-x 1 4984 users 1995 Apr 1 2014 masterha_check_repl
-rwxr-xr-x 1 4984 users 1779 Apr 1 2014 masterha_check_ssh
-rwxr-xr-x 1 4984 users 1865 Apr 1 2014 masterha_check_status
-rwxr-xr-x 1 4984 users 3201 Apr 1 2014 masterha_conf_host
-rwxr-xr-x 1 4984 users 2517 Apr 1 2014 masterha_manager
-rwxr-xr-x 1 4984 users 2165 Apr 1 2014 masterha_master_monitor
-rwxr-xr-x 1 4984 users 2373 Apr 1 2014 masterha_master_switch
-rwxr-xr-x 1 4984 users 5171 Apr 1 2014 masterha_secondary_check
-rwxr-xr-x 1 4984 users 1739 Apr 1 2014 masterha_stop
[root@mysql-C bin]# pwd
/opt/software/mha4mysql-manager-0.56/bin
[root@mysql-C bin]# cp * /usr/local/bin/
最后，在master和slave节点安装MHA客户端安装包：
[root@mysql-A bin]# tar -zxvf mha4mysql-node-0.56.tar.gz
[root@mysql-A bin]# cd mha4mysql-node-0.56
[root@mysql-A bin]# perl Makefile.PL
[root@mysql-A bin]# make
[root@mysql-A bin]# make install
创建ssh互信，在每个节点执行如下命令：
[root@mysql-A bin]# ssh-keygen
[root@mysql-A bin]# ssh-copy-id '-p 22 [email protected]'
[root@mysql-A bin]# ssh-copy-id '-p 22 [email protected]'
[root@mysql-A bin]# ssh-copy-id '-p 22 [email protected]'
配置主从复制：（略）
配置MHA管理脚本：
mkdir -p /mha/log ---这里是存放日志的文件夹路径
mkdir -p /etc/mha ---这里是存放配置文件的路径
touch /etc/mha/mha.conf
[root@mysql-C bin]# cat /etc/mha/mha.conf
[server default]
manager_log=/mha/log/mha.log //设置manager的日志
manager_workdir=/mha/ //设置manager的工作目录
user=admin //设置MHA管理账号
password=123456 //设置MHA管理账号密码
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railover
ping_type=CONNECT //定义故障切换和在线切换
master_ip_failover_script=/usr/local/bin/master_ip_failover //设置自动failover时候的切换脚本
master_ip_online_change_script=/usr/local/bin/master_ip_online_change //设置手动切换时候的切换脚本
remote_workdir=/mha/ //设置远端mysql在发生切换时binlog的保存位置
repl_password=repl //设置主从复制的账号
repl_user=repl //设置主从复制的账号密码
secondary_check_script=/usr/local/bin/masterha_secondary_check -s 192.168.165.137 -s 192.168.165.136
--user=root --master_host=mysql-A --master_ip=192.168.165.135 --master_port=3306
ssh_port=22
ssh_user=root [server1]
hostname=192.168.165.135
master_binlog_dir=/data/mysql/binlog
port=3306
ssh_port=22
candidate_master=1 [server2]
candidate_master=1
check_repl_delay=0
hostname=192.168.165.136
master_binlog_dir=/data/mysql/binlog
port=3306
ssh_port=22 [server3]
hostname=192.168.165.137
master_binlog_dir=/data/mysql/binlog
port=3306
ssh_port=22
设置relay log的清除方式（在每个slave节点上）：
mysql -e 'set global relay_log_purge=0'
设置定期清理relay脚本（两台slave服务器）
[root@mysql-C ~]# cat purge_relay_log.sh
#!/bin/bash
user=root
passwd=123456
port=3306
log_dir='/data/masterha/log'
work_dir='/data'
purge='/usr/local/bin/purge_relay_logs' if [ ! -d $log_dir ]
then
mkdir $log_dir -p
fi
$purge --user=$user --password=$passwd --disable_relay_log_purge --port=$port --workdir=$work_dir >> $log_dir/purge_relay_logs.log 2>&1
添加到crontab定期执行
[root@mysql-C ~]# crontab -l
0 4 * * * /bin/bash /root/purge_relay_log.sh
编辑自动切换脚本和手动切换脚本：
[root@mysql-C log]# cat /usr/local/bin/master_ip_failover
#!/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; my (
$command, $ssh_user, $orig_master_host,
$orig_master_ip, $orig_master_port, $new_master_host,
$new_master_ip, $new_master_port
); my $vip = '192.168.165.130';
my $ssh_start_vip = '/etc/init.d/keepalived start';
my $ssh_stop_vip = '/etc/init.d/keepalived stop'; GetOptions(
'command=s' => \$command,
'ssh_user=s' => \$ssh_user,
'orig_master_host=s' => \$orig_master_host,
'orig_master_ip=s' => \$orig_master_ip,
'orig_master_port=i' => \$orig_master_port,
'new_master_host=s' => \$new_master_host,
'new_master_ip=s' => \$new_master_ip,
'new_master_port=i' => \$new_master_port,
); exit &main(); sub main { print "\n\nIN SCRIPT TEST====$ssh_stop_vip==$ssh_start_vip===\n\n"; if ( $command eq "stop" || $command eq "stopssh" ) { # $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 \n";
&stop_vip();
$exit_code = 0;
# updating global catalog, etc
$exit_code = 0;
};
if ($@) {
warn "Got Error: $@\n";
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 \n";
&start_vip();
$exit_code = 0;
};
if ($@) {
warn $@; # If you want to continue failover, exit 10.
exit $exit_code;
}
exit $exit_code;
}
elsif ( $command eq "status" ) {
print "Checking the Status of the script.. OK \n";
# do nothing
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 {
"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";
}
[root@mysql-C log]# cat /usr/local/bin/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 $vip = '192.168.165.130';
my $key = '1';
my $ssh_start_vip = '/etc/init.d/keepalived start';
my $ssh_stop_vip = '/etc/init.d/keepalived stop';
my $ssh_user = 'root';
my $_tstart;
my $_running_interval = 0.1;
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 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";
#FIXME_xxx_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} );
} print "Disabling the VIP on old master: $orig_master_host \n";
&stop_vip(); ## 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(); ## 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";
$new_master_handler->disable_read_only(); ## Creating an app user on the new master
#print current_time_us() . " Creating app user on the new master..\n";
#FIXME_xxx_create_app_user($new_master_handler);
#$new_master_handler->enable_log_bin_local();
$new_master_handler->disconnect(); print "Enabling the VIP - $vip on the new master - $new_master_host \n";
&start_vip();
$exit_code = 0; ## 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;
}
} # 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 {
"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;
}
检查MHA Manger到所有MHA Node的SSH连接状态：
[root@mysql-C ~]# masterha_check_ssh --conf=/etc/mha/mha.conf
通过masterha_check_repl脚本查看整个集群的状态:
[root@mysql-C ~]# masterha_check_repl --conf=/etc/mha/mha.conf
报错：Can't exec "mysqlbinlog": No such file or directory at /usr/local/share/perl5/MHA/BinlogManager.pm line 99.
解决办法（所有节点）：
ln -s /usr/local/mysql/bin/mysqlbinlog /usr/local/bin/mysqlbinlog
ln -s /usr/local/mysql/bin/mysql /usr/local/bin/mysql
检查MHA Manager的状态：
通过master_check_status脚本查看Manager的状态：
[root@mysql-C ~]# masterha_check_status --conf=/etc/mha/mha.conf
mha is stopped(2:NOT_RUNNING).
安装keepalive：
yum install -y gcc openssl-devel kernel-devel net-snmp net-snmp-utils net-snmp-libs libnl libnl-devel
cd /usr/src/kernels/
ln -s 2.6.32-642.el6.x86_64/ /usr/src/linux
./configure --prefix=/usr/local/keepalived
make && make install
添加服务：
cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
mkdir /etc/keepalived
cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/
cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
配置keepalive：
[[email protected] ~]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived global_defs {
notification_email {
[email protected]
}
notification_email_from [email protected]
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id MySQL-HA
} vrrp_instance VI_1 {
state BACKUP
interface eth1
virtual_router_id 51
priority 120
advert_int 1
nopreempt authentication {
auth_type PASS
auth_pass 1111
} virtual_ipaddress {
192.168.165.130
}
}
启动/停止keepalive：
/etc/init.d/keepalived start
/etc/init.d/keepalived stop
启动/关闭MHA:
nohup /usr/local/bin/masterha_manager --conf=/etc/mha/mha.conf --ignore_last_failover </dev/null> /mha/log/mha.log 2>&1 &
masterha_stop --conf=/etc/mha/mha.conf
查看MHA状态信息：
[root@mysql-C ~]# masterha_master_monitor --conf=/etc/mha/mha.conf
MHA自动failover，手动failover，在线切换三种方式
手动切换脚本（当主库挂了）：
masterha_master_switch --master_state=dead --conf=/etc/mha/mha.conf --dead_master_host=192.168.165.136
--dead_master_port=3306 --new_master_host=192.168.165.135 --new_master_port=3306 --ignore_last_failover
在线平滑切换：
masterha_master_switch --conf=/etc/mha/mha.conf --master_state=alive --orig_master_is_new_slave
自动切换后恢复：
查看日志：
[root@mysql-C log]# grep -i "All other slaves should start" mha.log
Fri Dec 22 18:57:38 2017 - [info] All other slaves should start replication from here.
Statement should be: CHANGE MASTER TO MASTER_HOST='192.168.165.135', MASTER_PORT=3306,
MASTER_LOG_FILE='mysql-bin.000007', MASTER_LOG_POS=326, MASTER_USER='repl', MASTER_PASSWORD='xxx'; change master to
MASTER_HOST='192.168.165.135',
MASTER_PORT=3306,
MASTER_USER='repl',
MASTER_PASSWORD='repl',
MASTER_LOG_FILE='mysql-bin.000007',
MASTER_LOG_POS=326;
检查网卡上的虚拟ip
ip addr | grep eth1