mysql> install plugin rpl_semi_sync_master soname 'semisync_master.so';
mysql> set global rpl_semi_sync_master_enabled=1;
mysql> set global rpl_semi_sync_master_timeout=1000;
mysql> show global status like 'rpl%';

mysql> install plugin rpl_semi_sync_master soname 'semisync_master.so';
mysql> set global rpl_semi_sync_master_enabled=1;
mysql> set global rpl_semi_sync_master_timeout=1000;
mysql> install plugin rpl_semi_sync_slave soname 'semisync_slave.so';
mysql> set global rpl_semi_sync_slave_enabled=1;

mysql> install plugin rpl_semi_sync_slave soname 'semisync_slave.so';
mysql> set global rpl_semi_sync_slave_enabled=1;

mysql> grant replication slave on *.* to repl@'172.16.21.%' identified by 'repl';
mysql> show master status;
记录下 “File”和“Position”即当前主库使用的二进制日志名称和位置。

mysql> change master to master_host="172.16.21.23",master_user="repl",master_password="repl",master_log_file="bin-log.000001",master_log_pos=255;

mysql> grant replication slave on *.* to repl@'172.16.21.%' identified by 'repl';

mysql>start slave；
mysql>show slave status\G；
# 如果 Slave_IO_Running: Yes 和 Slave_SQL_Running: Yes 则说明主从配置成功
# 还可以到master上执行 Mysql>show global status like “rpl%”; 如果Rpl_semi_sync_master_clients 是2.说明半同步复制正常

apt-get install libdbd-mysql-perl
dpkg -i mha4mysql-node_0.54-0_all.deb

apt-get install libdbd-mysql-perl
apt-get install libconfig-tiny-perl
apt-get install liblog-dispatch-perl
apt-get install libparallel-forkmanager-perl
dpkg -i mha4mysql-manager_0.55-0_all.deb
mkdir -p /masterha/app1/

[server default]
manager_workdir=/masterha/app1
manager_log=/masterha/app1/manager.log
#remote_workdir=/usr/local/mysql
#mysql user and password
user=root
password=root
ssh_user=root
repl_user=repl
repl_password=repl
ping_interval=1
shutdown_script=""
#master_ip_failover_script=/usr/local/bin/master_ip_failover
#master_ip_online_change_script=/usr/local/bin/master_ip_online_change_script
#report_script=""[server1]
hostname=master
master_binlog_dir=/var/log/mysql
candidate_master=1[server2]
hostname=172.16.21.50
master_binlog_dir=/var/log/mysql
candidate_master=1
[server3]hostname=172.16.21.48
master_binlog_dir=/var/log/mysql
no_master=1

mysql> grant all on *.* to root@'172.16.21.15' identified by 'root';
mysql> grant all on *.* to root@'172.16.21.23' identified by 'root';
mysql> grant all on *.* to root@'172.16.21.50' identified by 'root';
mysql> grant all on *.* to root@'172.16.21.48' identified by 'root';

mysql> grant all on *.* to root@'172.16.21.%' identified by 'root';

ssh-keygen -t rsa
ssh-copy-id root@172.16.21.23
ssh-copy-id root@172.16.21.50
ssh-copy-id root@172.16.21.48

ssh-keygen -t rsa
ssh-copy-id root@172.16.21.50
ssh-copy-id root@172.16.21.48

ssh-keygen -t rsa
ssh-copy-id root@172.16.21.23
ssh-copy-id root@172.16.21.48

ssh-keygen -t rsa
ssh-copy-id root@172.16.21.23
ssh-copy-id root@172.16.21.50

masterha_check_ssh --conf=/etc/app1.cnf

masterha_check_repl --conf=/etc/app1.cnf

nohup masterha_manager --conf=/etc/app1.cnf < /dev/null > /masterha/app1/manager.log 2>&1 &

masterha_check_status --conf=/etc/app1.cnf

masterha_stop --conf=/etc/app1.cnf
# 如果不能停止， 加 --abort选项

00 00 * * * /usr/local/bin/purge_relay_logs –user=root –password=root –disable_relay_log_purge >> /var/log/purge_relay_logs.log 2>&1

测试和恢复MHA

manager上 tail -f /masterha/app1/manager.log 监控log

然后在master上 echo c > /proc/sysrq-trigger 使其死机

在log里可以看到master转移到备选master了

除了被动转移master,还可以手动转移master,如下：

masterha_master_switch --conf=/etc/app1.cnf --master_state=dead --dead_master_host=...
masterha_master_switch --conf=/etc/app1.cnf --master_state=alive --new_master_host=...

注：针对原来的MySQL主服务器是否已经宕机，执行命令所需的参数有所不同。

MHA有个不方便的地方是，无论宕机导致的master切换还是手动切换master, 原来的master都不在MHA架构内了，重新启动也不会加入，必须手动加入。

手动加入和上面的步骤类似，先把当前master数据复制到要加入的机器，然后change master,再start slave, 关键在做这一过程中，系统不能写入，这点要人命。

master_ip_failover, shutdown_script等脚本

MHA在配置文件里设置使得一些脚本在特定时候被执行

shutdown_script: MHA用于关闭master的脚本，在代码samples/scripts有一个样例脚本power_manager, 脚本详解可看:https://code.google.com/p/mysql-master-ha/wiki/Parameters#shutdown_script

master_ip_failover_script, master_ip_online_change_script: 发生在master切换的时候，为了应用继续可用，调用这两个脚本做些处理。refs:

说到Failover，通常有两种方式：一种是虚拟IP地址，一种是全局配置文件。
MHA并没有限定使用哪一种方式，而是让用户自己选择，虚拟IP地址的方式会牵扯到其它的软件，这里就不赘述了，
以下简单说说全局配置文件，以PHP为实现语言，代码如下：#!/usr/bin/env php
<?php
$longopts = array('command:','ssh_user:','orig_master_host:','orig_master_ip:','orig_master_port:','new_master_host::','new_master_ip::','new_master_port::',
);$options = getopt(null, $longopts);if ($options['command'] == 'start') {$params = array('ip'   => $options['new_master_ip'],'port' => $options['new_master_port'],);$string = '<?php return ' . var_export($params, true) . '; ?>';file_put_contents('config.php', $string, LOCK_EX);
}exit(0);
?>
注：用其它语言实现这个脚本也是OK的，最后别忘了给脚本加上可执行属性。如果要测试效果的话，可以kill掉当前的MySQL主服务器，稍等片刻，MHA就会把某台MySQL从服务器提升为新的MySQL主服务器，
并调用master_ip_failover_script脚本，
如上所示，我们在master_ip_failover_script脚本里可以把新的MySQL主服务器的ip和port信息持久化到配置文件里，
这样应用就可以使用新的配置了。有时候需要手动切换MySQL主服务器，可以使用masterha_master_switch命令，
不过它调用的不是master_ip_failover_script脚本，而是master_ip_online_change_script脚本，但调用参数类似，脚本可以互用。

虚拟ip涉及到其他软件，我们稍后讲

report_script: You might want to send a report (i.e. e-mail) when failover has completed or ended with errors. 接受如下参数：

--orig_master_host=(dead master's hostname)
--new_master_host=(new master's hostname)
--new_slave_hosts=(new slaves' hostnames, delimited by commas)
--subject=(mail subject)
--body=(body)

这些脚本在代码包里都有示例，但都是perl的，你可以用其他脚本语言自己来写。

/sbin/ifconfig eth0:1 172.16.21.119/24

/sbin/ifconfig eth0:1 down

auto lo
iface lo inet loopbackauto eth0:0
iface eth0:0 inet static
name Ethernet alias LAN card
address 10.112.18.191
netmask 255.255.255.0
broadcast 10.112.18.255
network 10.112.18.0

#!/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 = '172.16.21.119/24';  # Virtual IP
my $key = "1";
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" ) {# $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;};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 $@;exit $exit_code;}exit $exit_code;}elsif ( $command eq "status" ) {print "Checking the Status of the script.. OK \n";`ssh $ssh_user\@cluster1 \" $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\n";
}

master_ip_failover_script=/usr/local/bin/master_ip_failover
master_ip_online_change_script=/usr/local/bin/master_ip_online_change_script