编者按:很多朋友一开始接触MySQL双机同步需求的时候可能会感到不知道从哪里入手,事实上这是MySQL本身就支持的功能之一。本文提供有关MySQL主从同步的初步思路,供大家参考。

一.需求问题
假设目前有两台 MySQL 数据库服务器,如何实现这两台机器的数据同步问题?即在一台机器上修改数据库后,另一台机器会同步更新所修改的信息。
二.解决方案
查资料发现 MySQL 支持单向,异步复制,复制过程中一个服务器充当主服务器,而另一个或多个其他服务器充当从服务器。
原理是这样的:
主服务器将更新写入二进制日志文件,并维护文件的一个索引来跟踪日志循环。这些日志可以记录发送到从服务器的更新。当一个从服务器连接主服务器时,它通知主服务器从服务器在日志中读取的最后一次成功更新的位置。从服务器接受从那时起发生的任何更新,然后封锁并等待主服务器通知新的更新。
2.1 测试环境
- Master : 192.168.7.67 (CentOS 5.5 x86_64 ) MySQL Version : 5.0.77
 - Slave: 192.168.56.103 (CentOS 5.3 i386) MySQL Version : 5.0.45
 
备注:
Master 和 slave 端的 MySQL 版本最好要一样的,或者 Master 端的版本高于 Slave 端
2.2 配置过程
2.2.1 Master 端设置
开启 MySQL 服务并新建一个测试数据库 abc:
- root@camlit ~: /etc/init.d/mysqld start
 - jian.ma@camlit ~: mysql -u root -p
 - Enter password: xxxx
 - Welcome to the MySQL monitor. Commands end with ; or \g.
 - Your MySQL connection id is 3
 - Server version: 5.0.77 Source distribution
 - Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
 - mysql> create database abc;
 - Query OK, 1 row affected (0.31 sec)
 - ###创建一个用来同步的用户,指定只能在 192.168.56.103 登录
 - ###REPLICATION SLAVE: Enable replication slaves to read binary log events from the master
 - mysql> grant replication slave on *.* to 'test1'@'192.168.56.103' identified by 'test1';
 - Query OK, 0 rows affected (0.16 sec)
 
修改配置文件:
- root@camlit ~: vi /etc/my.cnf
 
备注:在修改配置文件之前做好该文件的备份工作。
- [mysqld]
 - datadir=/var/lib/mysql
 - socket=/var/lib/mysql/mysql.sock
 - user=mysql
 - old_passwords=1
 - ##增加下面内容
 - server_id=1###1 表示 master, 2 表示 slave binlog-do-db=abc ###需要同步的数据库,如果有多个数据库,每个数据库一行 binlog-ignore-db=mysql###不需要同步的数据库 log-bin=mysql-bin
 - [mysqld_safe]
 - log-error=/var/log/mysqld.log
 - pid-file=/var/run/mysqld/mysqld.pid
 
重启服务:
- root@camlit ~: /etc/init.d/mysqld restart
 
2.2.2 Slave 端设置
和 master 端一样创建一个相同的数据库: abc
- Enter password:
 - Welcome to the MySQL monitor. Commands end with ; or \g.
 - Your MySQL connection id is 5
 - Server version: 5.0.45-log Source distribution
 - Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
 - mysql> create database abc;
 - Query OK, 1 row affected (0.31 sec)
 
修改配置文件:
- root@test2 ~: vi /etc/my.cnf
 
- [mysqld]
 - datadir=/var/lib/mysql
 - socket=/var/lib/mysql/mysql.sock
 - user=mysql
 - old_passwords=1
 - ###增加下面内容
 - server_id=2 log-bin=mysql-bin master-host=192.168.7.67 master-user=test1 master-password=test1 master-port=3306 master-connect-retry=10 ###连接次数 replicate-do-db=abc ###接受的数据库名 replicate-ignore-db=mysql ###不要接受的数据库
 - [mysqld_safe]
 - log-error=/var/log/mysqld.log
 - pid-file=/var/run/mysqld/mysqld.pid
 
重启服务:
- root@test2~: /etc/init.d/mysqld restart
 
备注:
配置成功 后会在 mysql 目录(/var/lib/mysql/)下生成 master.info 文件,如果要更改 slave 设置,要先将该文件删除才会起作用。
进入 mysql,输入下面命令:
- root@test2~: mysql -u root -p
 - Enter password:
 - Welcome to the MySQL monitor. Commands end with ; or \g.
 - Your MySQL connection id is 4
 - Server version: 5.0.45-log Source distribution
 - Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
 - mysql> slave start;
 - Query OK, 0 rows affected, 1 warning (0.00 sec)
 - ###查看同步情况
 - mysql > show slave status; 或 show master status;
 
2.3 结果测试
在 Master 端进行数据库 abc 的一些操作,如下所示:
- jian.ma@camlit ~: mysql -u root -p
 - Enter password:
 - Welcome to the MySQL monitor. Commands end with ; or \g.
 - Your MySQL connection id is 3
 - Server version: 5.0.77-log Source distribution
 - Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
 - mysql> use abc;
 - Database changed
 - mysql> create table test1 (IP VARCHAR(20),USER VARCHAR(100), MAIL
 - VARCHAR(100));
 - Query OK, 0 rows affected (1.20 sec)
 - mysql> insert into test1(IP,USER,MAIL) values('192.168.7.66', 'test', 'test@test.com.cn');
 - Query OK, 1 row affected (0.06 sec)
 
在 Slave 端查看是否能够更新:
- root@test2 ~: mysql -u root -p
 - Enter password:
 - Welcome to the MySQL monitor. Commands end with ; or \g.
 - Your MySQL connection id is 6
 - Server version: 5.0.45-log Source distribution
 - Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
 - mysql> show databases;
 - +--------------------+
 - | Database |
 - +--------------------+
 - | information_schema |
 - | foo|
 - | mysql |
 - | test |
 - |abc |
 - +--------------------+
 - 5rows in set (0.00 sec)
 - mysql> use abc;
 - Reading table information for completion of table and column names
 - You can turn off this feature to get a quicker startup with -A
 - Database changed
 - mysql> show tables;
 - +---------------+
 - | Tables_in_abc |
 - +---------------+
 - | test1 |
 - +---------------+
 - 1 row in set (0.03 sec)
 - mysql> select * from test1;
 - +--------------+------+------------------+
 - | IP | USER | MAIL |
 - +--------------+------+------------------+
 - | 192.168.7.66 | test | test@test.com.cn |
 - +--------------+------+------------------+
 - 1 row in set (0.00 sec)
 
从上面的结果可以看到 Master 端的数据可以同步到 Slave 端里面。说明此时主从数据库的同步问题已经成功解决。
#p#
三.补充资料
关于如何连接到远程 MySQL 问题,可以采取下面的步骤:
首先先登录到远程机器:
- jian.ma@camlit ~: ssh root@192.168.56.103
 - password: xxx
 - root@test2 ~:
 
编辑配置文件:
- root@test2 ~: vi /etc/my.cnf
 
增加下面一行内容:
- [mysqld]
 - datadir=/var/lib/mysql
 - socket=/var/lib/mysql/mysql.sock
 - user=mysql
 - old_passwords=1
 - bind-address=192.168.56.103###此 IP 地址为 MySQL 本机的 IP 地址
 - [mysqld_safe]
 - log-error=/var/log/mysqld.log
 - pid-file=/var/run/mysqld/mysqld.pi
 
重启服务:
- root@test2 ~: /etc/init.d/mysqld restart
 
创建测试数据库:
- root@test2 ~: mysql -u root -p
 - Enter password:
 - Welcome to the MySQL monitor. Commands end with ; or \g.
 - Your MySQL connection id is 2
 - Server version: 5.0.45 Source distribution
 - Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
 - mysql> create database foo ;
 - Query OK, 1 row affected (0.00 sec)
 - ###增加用户 test123 从任何主机登录到 MySQL
 - mysql> grant all privileges on *.* to 'test123'@'%' identified by 'test123' with grant option;
 - Query OK, 0 rows affected (0.00 sec)
 - ###增加用户 test1 从 192.168.7.67 主机登录到 MySQL
 - mysql> grant all privileges on foo.* to 'test1'@'192.168.7.67' identified by 'test1' with grant option;
 - Query OK, 0 rows affected (0.00 sec)
 
如果有防火墙的设置的话,可以如下设置:
- root@test2 ~: iptables -A INPUT -i eth0 -s 192.168.7.67 -p tcp --dport 3306 -j ACCEPT
 - root@test2~: /etc/init.d/iptales save
 
最后在客户端就可以输入下面命令来远程进入 MySQL 数据库:
- jian.ma@camlit ~: mysql -u test1 -h 192.168.56.103 -p
 - Enter password:
 - Welcome to the MySQL monitor. Commands end with ; or \g.
 - Your MySQL connection id is 13
 - Server version: 5.0.45 Source distribution
 - Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
 
mysqld.pl内容如下:
- #!/usr/bin/perl
 - #This script is used to check if the mysql replication is ok
 - use strict;
 - use DBI;
 - use POSIX "strftime";
 - my $host = "192.168.56.103";
 - my $user = "test1";
 - my $passwd = "test1";
 - my $port = "3306";
 - my $max_behind = "120";
 - my $check_log = "./mysql_check.log";
 - #Open the log file
 - open (FH, ">> $check_log") or die $!;
 - #Connect the mysql server
 - my $dbh = &MysqlConnect ($host, $port, $user, $passwd);
 - #Get slave sql status
 - my $slave_status = &MysqlQuery( $dbh, 'show slave status');
 - print FH "Error: SQL Query Error:" . $dbh->errstr;
 - my $slave_IO = $slave_status->{Slave_IO_Running};
 - my $slave_SQL = $slave_status->{Slave_SQL_Running};
 - my $seconds_behind_master = $slave_status->{Seconds_Behind_Master};
 - my $now_time = POSIX::strftime ("[%Y-%m-%d %H:%M:%S]", localtime);
 - print "Check the Slave MySQL stauts....\n";
 - print "_" x 50, "\n";
 - print "Time:\t\t\t$now_time\n";
 - print "Slave IO Running:\t\t$slave_IO\n";
 - print "Slave SQL Running::\t\t$slave_SQL\n";
 - print "Behind Master Seconds:\t\t$seconds_behind_master\n";
 - if ($seconds_behind_master > $max_behind){
 - print "Slave SQL Server is far behind master ";
 - }
 - #---Functions----#
 - sub MysqlConnect {
 - my ($host, $port, $user, $passwd) = @_;
 - my $dsn = "DBI:mysql:host=$host;port=$port";
 - return DBI->connect($dsn, $user, $passwd, {RaiseError => 1});
 - }
 - sub MysqlQuery {
 - my ($dbh , $query) = @_;
 - my $sth = $dbh->prepare($query);
 - my $res = $sth->execute;
 - return undef unless $res;
 - my $row = $sth->fetchrow_hashref;
 - $sth->finish;
 - return $row;
 - }
 
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