MySQL主从双向复制(脚本实现)
1主服务器的主机名为：master，从服务器的主机名为：slave
2安装MYSQL包
# rpm –ivh mysql-5.0.77-4.2.1.AXS3.i386.rpm
3在主库启动MYSQL
#service mysql start
4在主库编辑/etc/my.cnf,
#vim /etc/my.cnf
在[mysqld]配置段添加如下字段
server-id=1
log-bin=cjxylog
编辑好my.cnf后重启mysql
#service mysqld restart
5主库增加用户，用于从库读取主库日志
>grant replication slave on *.* to 'slave'@'10.10.10.52' identified by 'slave';
启动后用show master status查看主库的日志文件
#mysql
>show master status
6启动从库的mysql
#service mysqld start
7修改从库/etc/my.cnf,增加选项：
#Mysql
#vim /etc/my.cnf
添加如下内容
server-id=2
master-host=10.10.10.51
master-user=slave
master-password=slave
master-port=3306
master-connect-retry=60
编辑完后重启mysql
#service mysqld restart
8重启后用show命令查看从库slave的运行情况
#mysql
>stop slave;
>start slave;
>show slave status\G;
9测试
主库创建名为cjxy的数据库并用show databases；命令查看
#mysql
>start master
>create database cjxy;
>show databases;
从库只须用show命令查看即可
#mysql
>show databases;
10单向复制成功,编写脚本,实现主从双向复制和故障自动切换角色 ,从而实现MYSQL数据库高可用性.
在两台MYSQL服务器上配置3份MYSQL服务配置文件
分别为：
/etc/my.cnf
/etc/my.cnf.master
/etc/my.cnf.slave
其中，原主库服务器（IP地址：10.10.10.51）配置文件内容如下：
/etc/my.cnf
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
server-id=1
log-bin=cjxylog
# Default to using old password format for compatibility with mysql 3.x
# clients (those using the mysqlclient10 compatibility package).
old_passwords=1
# Disabling symbolic-links is recommended to prevent assorted security risks;
# to do so, uncomment this line:
# symbolic-links=0
[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
/etc/my.cnf.master
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
server-id=1
log-bin=cjxylog
# Default to using old password format for compatibility with mysql 3.x
# clients (those using the mysqlclient10 compatibility package).
old_passwords=1
# Disabling symbolic-links is recommended to prevent assorted security risks;
# to do so, uncomment this line:
# symbolic-links=0
[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
/etc/my.cnf.slave
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
server-id=2
master-host=10.10.10.52
master-user=slave
master-password=slave
master-port=3306
master-connect-retry=60
# Default to using old password format for compatibility with mysql 3.x
# clients (those using the mysqlclient10 compatibility package).
old_passwords=1
# Disabling symbolic-links is recommended to prevent assorted security risks;
# to do so, uncomment this line:
# symbolic-links=0
[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
原从库服务器（IP地址：10.10.10.52）配置文件内容如下：
/etc/my.cnf
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
server-id=2
master-host=10.10.10.51
master-user=slave
master-password=slave
master-port=3306
master-connect-retry=60
# Default to using old password format for compatibility with mysql 3.x
# clients (those using the mysqlclient10 compatibility package).
old_passwords=1
# Disabling symbolic-links is recommended to prevent assorted security risks;
# to do so, uncomment this line:
# symbolic-links=0
[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
/etc/my.cnf.master
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
server-id=1
log-bin=swaplog
# Default to using old password format for compatibility with mysql 3.x
# clients (those using the mysqlclient10 compatibility package).
old_passwords=1
# Disabling symbolic-links is recommended to prevent assorted security risks;
# to do so, uncomment this line:
# symbolic-links=0
[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
/etc/my.cnf.slave
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
server-id=2
master-host=10.10.10.51
master-user=slave
master-password=slave
master-port=3306
master-connect-retry=60
# Default to using old password format for compatibility with mysql 3.x
# clients (those using the mysqlclient10 compatibility package).
old_passwords=1
# Disabling symbolic-links is recommended to prevent assorted security risks;
# to do so, uncomment this line:
# symbolic-links=0
[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
服务器主从自动切换，当数据库服务器有一台离线，另外一台可以上线开始工作，实现高可用。
首先在原主库服务器（IP地址：10.10.10.51）上写入脚本，当主库服务器与WEB服务器失去联系后自动变成从属服务器（如果此服务器没有宕机）
脚本内容如下:
#/bin/bash
#原MYSQL 主服务器使用的脚本
check=`cat /etc/my.cnf | grep server-id`
if [ "$check" = "server-id=1" ]
then
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
if [ "$link" != "10.10.10.100:" ]
then
link=`ping -c 1 10.10.10.52 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.52 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.52 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.52 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.52 | grep "from" | awk '{print $4}'`
if [ "$link" = "10.10.10.52:" ]
then
Ifdown eth0:200
cat /etc/my.cnf.slave > /etc/my.cnf
service mysqld restart
fi
else
fi
else
link=`ping -c 1 10.10.10.52 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.52 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.52 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.52 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.52 | grep "from" | awk '{print $4}'`
if [ "$link" != "10.10.10.52:" ]
then
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
if [ "$link" = "10.10.10.100:" ]
then
ifconfig eth0:200 10.10.10.200 netmask 255.255.255.0
cat /etc/my.cnf.master > /etc/my.cnf
service mysqld restart
fi
else
fi
fi
然后在从服务器（IP地址：10.10.10.52）写入脚本，当从库与主库失去联系后，从库自动变成主库
脚本内容如下：
#/bin/bash
#原MYSQL从服务器使用的脚本
check=`cat /etc/my.cnf | grep server-id`
if [ "$check" != "server-id=1" ]
then
link=`ping -c 1 10.10.10.51 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.51 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.51 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.51 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.51 | grep "from" | awk '{print $4}'`
if [ "$link" != "10.10.10.51:" ]
then
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
if [ "$link" = "10.10.10.100:" ]
ifconfig eth0:200 10.10.10.200 netmask 255.255.255.0
cat /etc/my.cnf.master > /etc/my.cnf
service mysqld restart
fi
else
fi
else
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.100 | grep "from" | awk '{print $4}'`
if [ "$link" != "10.10.10.100:" ]
link=`ping -c 1 10.10.10.51 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.51 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.51 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.51 | grep "from" | awk '{print $4}'`
link=`ping -c 1 10.10.10.51 | grep "from" | awk '{print $4}'`
if [ "$link" = "10.10.10.51:" ]
then
Ifdown eth0:200
cat /etc/my.cnf.slave > /etc/my.cnf
service mysqld restart
fi
else
fi
fi
将以上脚本分别命名并放置在/opt/mysqlchange.sh
并且赋予执行权限 chmod a+x /opt/mysqlchange.sh
然后启动循环任务计划，每一分钟执行一次该脚本
Crontab –e
*/1 * * * * bash /opt/mysqlchange.sh
注:
一些错误信息的处理，主从服务器上的命令，及状态信息。
在从服务器上使用show slave status\G
Slave_IO_Running, 为No,
则说明IO_THREAD没有启动，请执行start slave io_thread
Slave_SQL_Running为 No
1.首先停掉Slave服务：slave stop
2.到主服务器上查看主机状态：
记录File和Position对应的值。
mysql> show master status;
+------------------+-----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+-----------+--------------+------------------+
| mysql-bin.000020 | 135617781 | | |
+------------------+-----------+--------------+------------------+
1 row in set (0.00 sec)
3.到slave服务器上执行手动同步：
mysql> change master to
> master_host='master_ip',
> master_user='user',
> master_password='pwd',
> master_port=3307,
> master_log_file='mysql-bin.000020',
> master_log_pos=135617781;
1 row in set (0.00 sec)
> slave start;
1 row in set (0.00 sec)
再次查看slave状态发现：
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
..
Seconds_Behind_Master: 0