mha搭建步骤

1. 建立DB节点
（其中2台为master，另一台为slave）；
以master1作为主库

master1特殊配置：
# custom
server-id = 1001
log_bin = mysql-bin
log_bin_index = mysql-bin.index
log-slave-updates
sync_binlog = 1
auto_increment_increment = 2
auto_increment_offset = 1
skip_slave_start
read_only = 1

master2特殊配置
# custom
server-id = 1002
log_bin = mysql-bin
log_bin_index = mysql-bin.index
log-slave-updates
sync_binlog = 1
auto_increment_increment = 2
auto_increment_offset = 2
read_only = 1

slave特殊配置
# custom
server-id = 1003
log_bin = mysql-bin
log_bin_index = mysql-bin.index
#log-slave-updates
sync_binlog = 1
read_only = 1


2. 安装node
https://mysql-master-ha.googlecode.com/files/mha4mysql-node-0.54-0.el6.noarch.rpm
shell> yum install perl-DBD-MySQL
rpm -ivh mha4mysql-node-0.54-0.el6.noarch.rpm

3. 安装manager
https://mysql-master-ha.googlecode.com/files/mha4mysql-manager-0.55-0.el6.noarch.rpm
shell> yum install perl-DBD-MySQL
shell> yum install perl-Config-Tiny
shell> yum install perl-Log-Dispatch
shell> yum install perl-Parallel-ForkManager
shell> yum install perl-Time-HiRes
rpm -ivh mha4mysql-node-0.54-0.el6.noarch.rpm
rpm -ivh mha4mysql-manager-0.55-0.el6.noarch.rpm

4. 配置mha
为确保结构不被破坏，使用1主2从的架构，同时其中一台slave不作为高可用切换的候选节点，即主从切换只在固定的2台之间进行

4.1 default全局配置
[server default]
user=root
password=
ssh_user=root
repl_user=replication
repl_password=123456
ping_interval=1
#master_ip_online_change_script=""
#master_ip_failover_script=""

[server1]
hostname = 192.168.1.100
port = 3306
master_binlog_dir = /var/lib/mysql
candidate_master = 1

[server2]
hostname = 192.168.1.101
port = 3306
master_binlog_dir = /var/lib/mysql
candidate_master = 1

[server3]
hostname = 192.168.1.102
port = 3306
master_binlog_dir = /var/lib/mysql
no_master = 1

5. 切换方法
5.1 在线切换——保留原master节点
masterha_master_switch --master_state=alive   --conf=/etc/mha.cnf  --new_master_host=192.168.1.101 --orig_master_is_new_slave

这个切换可以随时执行，不需要manager处于运行中，期间会询问几次yes/no；
需要注意的是，在线切换时，如果没有online_change脚本处理对应逻辑的话，工具本身并不会将旧的master置为read_only，只会把新的master置为read_only=0，最好先把原主库read_only设置为1

5.2 离线切换