MHA是一位日本人用Perl写的一套MySQL故障切换方案，来保证数据库系统的高可用.在宕机的时间内（通常10—60秒内），完成故障切换，部署MHA，可避免主从一致性问题，节约购买新服务器的费用，不影响服务器性能，易安装，不改变现有部署。
还支持在线切换，从当前运行master切换到一个新的master上面，只需要很短的时间（0.5-2秒内），此时仅仅阻塞写操作，并不影响读操作，便于主机硬件维护。
yum install perl-DBD-MySQL /perl-Config-Tiny perl-Log-Dispatch /perl-Parallel-ForkManager -yyum install perl-Time-HiRes perl-Parallel-ForkManager -ywget http://mysql-master-ha.googlecode.com/files/mha4mysql-manager-0.55-0.el6.noarch.rpmwget http://mysql-master-ha.googlecode.com/files/mha4mysql-node-0.54-0.el6.noarch.rpmrpm -ivh mha4mysql-node-0.54-0.el6.noarch.rpmrpm -ivh mha4mysql-manager-0.55-0.el6.noarch.rpm
mkdir /etc/masterhavi /etc/masterha_default.cnf [server default]user=managerpassword=test_2014ping_interval=1repl_user=reprepl_password=rep_2014
ssh 证书安装：
root 用户下执行：
ssh-keygen -t rsa
拷贝 id_rsa.pub 到数据库节点机器上的/tmp 目录下，在数据库节点机器上执行：
cd /root/.sshcat /tmp/id_rsa.put >>authorized_keyschmod 600 authorized_keys
wget http://mysql-master-ha.googlecode.com/files/mha4mysql-node-0.54-0.el6.noarch.rpmyum install perl-DBD-MySQL -yrpm -ivh mha4mysql-node-0.54-0.el6.noarch.rpm
在数据库节点上以root 用户执行：
ssh-keygen -t rsa
分别拷贝id_rsa.pub 到对方机器的/tmp 目录下，然后分别执行：
cd /root/.sshcat /tmp/id_rsa.put >>authorized_keyschmod 600 authorized_keys
在master 上执行下面命令（第一次启用必须配置手动配置vip address）：
ifconfig eth1:2 10.10.0.102/16
在 mha 管理节点上编辑配置文件：
vi /etc/masterha/test.conf [server default]ssh_user=rootping_interval=1report_script=/usr/local/bin/send_reportmaster_ip_failover_script=/usr/local/bin/master_ip_failovermaster_ip_online_change_script=/usr/local/bin/master_ip_failover[server1]hostname=10.10.0.101master_binlog_dir=/log/mysql_testcandidate_master=1port=3306ssh_port=22[server2]hostname=10.10.0.100master_binlog_dir=/log/mysql_testcandidate_master=1port=3306ssh_port=22
主从执行：
mysql>grant replication slave on *.* to rep@'10.10.%' identified by 'rep_2014' ;mysql>grant all on *.* to manager@'10.10.%' identified by 'test_2014' ;mysql>flush privileges;
主上执行：
mysql>show master status;
从上执行：
mysql>change master to master_host='10.10.0.101',master_port=3306,master_user='rep',master_password='rep_2014', master_log_file='mysql-bin.000004',master_log_pos=402; mysql> start slave;mysql> stop slave;mysql> reset slave;mysql> show slave status/G;
测试ssh 配置：
/usr/bin/masterha_check_ssh --conf=/etc/masterha/test.conf
测试复制：
/usr/bin/masterha_check_repl --conf=/etc/masterha/test.conf
启用 mha ：
masterha_manager --conf=/etc/masterha/test.conf
master 切换：
masterha_master_switch --master_state=alive --conf=/etc/masterha/test.conf
master_ip_failover 脚本：
cat /usr/local/bin/master_ip_failover#!/usr/bin/env perluse 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 = '10.10.0.102/16'; # Virtual IPmy $key = "2";my $ssh_start_vip = "/sbin/ifconfig eth1:$key $vip";my $ssh_stop_vip = "/sbin/ifconfig eth1:$key down";$ssh_user = "root";GetOptions( 'command=s' => /$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 mastersub start_vip() { `ssh $ssh_user/@$new_master_host /" $ssh_start_vip /"`;}# A simple system call that disable the VIP on the old_mastersub 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";} cat send_report #!/usr/bin/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;#new_master_host and new_slave_hosts are set only when recovering master succeededmy ( $dead_master_host, $new_master_host, $new_slave_hosts, $subject, $body );GetOptions( 'orig_master_host=s' => /$dead_master_host, 'new_master_host=s' => /$new_master_host, 'new_slave_hosts=s' => /$new_slave_hosts, 'subject=s' => /$subject, 'body=s' => /$body,);# Do whatever you want hereexit 0;下载本文