MySQL主从

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一、主从简介

2. 主从形式
一主一从
主主复制
一主多从—扩展系统读取的性能，因为读是在从库读取的
多主一从—5.7开始支持

3.主从复制原理
主从复制步骤：
主库将所有的写操作记录到binlog日志中并生成一个log dump线程，将binlog日志传给从库的I/O线程
从库生成两个线程，一个I/O线程，一个SQL线程
I/O线程去请求主库的binlog，并将得到的binlog日志写到relay log（中继日志） 文件中
SQL线程，会读取relay log文件中的日志，并解析成具体操作，来实现主从的操作一致，达到最终数据一致的目的

二、主从复制配置

主从复制配置步骤：
1.确保从数据库与主数据库里的数据一样
2.在主数据库里创建一个同步账号授权给从数据库使用
3.配置主数据库（修改配置文件）
4.配置从数据库（修改配置文件）
需求：
搭建两台MySQL服务器，一台作为主服务器，一台作为从服务器，主服务器进行写操作，从服务器进行读操作
环境说明：

主数据库

//全备主库，全备主库时需要另开一个终端，给数据库加上读锁，避免在备份期间有其他人在写入导致数据不一致，退出数据库即可解锁 [root@mysql ~]# mysql -uroot -p mysql> flush tables with read lock; Query OK, 0 rows affected (0.00 sec)//此锁表的终端必须在备份完成以后才能退出 //在锁打开情况下进行全备 [root@mysql ~]# mysqldump -uroot -predhat --all-databases > /opt/all-4.sql mysqldump: [Warning] Using a password on the command line interface can be insecure. [root@mysql ~]# ll /opt/all-4.sql -rw-r--r-- 1 root root  Aug 6 08:54 /opt/all-4.sql //发送到从库 [root@mysql ~]# scp /opt/all-4.sql root@192.168.35.143:/opt/ //在主数据库里创建一个同步账号授权给从数据库使用 [root@mysql ~]# mysql -uroot -p mysql> create user 'repl'@'192.168.35.143' identified by 'redhat'; //创建用户 Query OK, 0 rows affected (0.00 sec) mysql> grant replication slave on *.* to 'repl'@'192.168.35.143'; //赋权 Query OK, 0 rows affected (0.00 sec) mysql> flush privileges; //刷新 Query OK, 0 rows affected (0.00 sec) //配置主数据库 [root@mysql ~]# vim /etc/my.cnf [mysqld] datadir=/var/lib/mysql socket=/var/lib/mysql/mysql.sock log-bin=mysql-bin //启用binlog日志 server-id=1 //数据库服务器唯一标识符，主库的server-id值必须比从库的小 symbolic-links=0 //符号链接 log-error=/var/log/mysqld.log //错误日志 pid-file=/var/run/mysqld/mysqld.pid //重启服务，查看端口 [root@mysql ~]# systemctl restart mysqld [root@mysql ~]# ss -antl State Recv-Q Send-Q Local Address:Port Peer Address:Port Process LISTEN 0 5 0.0.0.0:873 0.0.0.0:* LISTEN 0 128 0.0.0.0:22 0.0.0.0:* LISTEN 0 5 127.0.0.1:25151 0.0.0.0:* LISTEN 0 5 [::]:873 [::]:* LISTEN 0 511 *:80 *:* LISTEN 0 128 [::]:22 [::]:* LISTEN 0 511 *:443 *:* LISTEN 0 80 *:3306 *:* //查看数据库状态 [root@mysql ~]# mysql -uroot -p mysql> show master status; +------------------+----------+--------------+------------------+-------------------+ | File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set | +------------------+----------+--------------+------------------+-------------------+ | mysql-bin.000001 | 154 | | | | +------------------+----------+--------------+------------------+-------------------+ 

从数据库

//恢复数据 [root@mysql2 ~]# mysql -uroot -predhat < /opt/all-4.sql mysql: [Warning] Using a password on the command line interface can be insecure. //进入数据库，查看主库数据是否一致 mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | lsy | | mysql | | performance_schema | | sys | +--------------------+ 5 rows in set (0.00 sec) mysql> use lsy; 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> select * from student; +----+------+------+ | id | name | age | +----+------+------+ | 1 | tom | 20 | | 2 | sam | 22 | | 3 | sdam | 23 | +----+------+------+ 3 rows in set (0.00 sec) //配置从数据库 [root@mysql2 ~]# vim /etc/my.cnf [mysqld] datadir=/var/lib/mysql socket=/var/lib/mysql/mysql.sock server-id=2 //设置从库的唯一标识符，从库的server-id值必须大于主库的该值 relay-log=mysql-relay-bin //启用中继日志relay-log symbolic-links=0 //符号链接 log-error=/var/log/mysqld.log //错误日志 pid-file=/var/run/mysqld/mysqld.pid //重启服务 [root@mysql2 ~]# systemctl restart mysqld [root@mysql2 ~]# ss -antl State Recv-Q Send-Q Local Address:Port Peer Address:Port Process LISTEN 0 128 0.0.0.0:22 0.0.0.0:* LISTEN 0 80 *:3306 *:* LISTEN 0 128 [::]:22 [::]:* //配置并启动主从复制 mysql> change master to master_host='192.168.35.142',master_user='repl',master_password='redhat',master_log_file='mysql-bin.000001',master_log_pos=154; //查看服务器状态，只需关注以下两点即可 Slave_IO_Running: Yes Slave_SQL_Running: Yes 

验证

//主数据库添加数据，从数据同步数据即可 //查看日志文件看数据是否同步 //主数据库日志 mysql> show binlog events in 'mysql-bin.000001'; +------------------+-----+----------------+-----------+-------------+---------------------------------------+ | Log_name | Pos | Event_type | Server_id | End_log_pos | Info | +------------------+-----+----------------+-----------+-------------+---------------------------------------+ | mysql-bin.000001 | 4 | Format_desc | 1 | 123 | Server ver: 5.7.37-log, Binlog ver: 4 | | mysql-bin.000001 | 123 | Previous_gtids | 1 | 154 | | | mysql-bin.000001 | 154 | Anonymous_Gtid | 1 | 219 | SET @@SESSION.GTID_NEXT= 'ANONYMOUS' | | mysql-bin.000001 | 219 | Query | 1 | 290 | BEGIN | | mysql-bin.000001 | 290 | Table_map | 1 | 343 | table_id: 108 (lsy.student) | | mysql-bin.000001 | 343 | Write_rows | 1 | 388 | table_id: 108 flags: STMT_END_F | | mysql-bin.000001 | 388 | Xid | 1 | 419 | COMMIT /* xid=22 */ | +------------------+-----+----------------+-----------+-------------+---------------------------------------+ //从数据库日志 mysql> show relaylog events in 'mysql-relay-bin.000002'; +------------------------+-----+----------------+-----------+-------------+---------------------------------------+ | Log_name | Pos | Event_type | Server_id | End_log_pos | Info | +------------------------+-----+----------------+-----------+-------------+---------------------------------------+ | mysql-relay-bin.000002 | 4 | Format_desc | 2 | 123 | Server ver: 5.7.37, Binlog ver: 4 | | mysql-relay-bin.000002 | 123 | Previous_gtids | 2 | 154 | | | mysql-relay-bin.000002 | 154 | Rotate | 1 | 0 | mysql-bin.000001;pos=154 | | mysql-relay-bin.000002 | 201 | Format_desc | 1 | 0 | Server ver: 5.7.37-log, Binlog ver: 4 | | mysql-relay-bin.000002 | 320 | Anonymous_Gtid | 1 | 219 | SET @@SESSION.GTID_NEXT= 'ANONYMOUS' | | mysql-relay-bin.000002 | 385 | Query | 1 | 290 | BEGIN | | mysql-relay-bin.000002 | 456 | Table_map | 1 | 343 | table_id: 108 (lsy.student) | | mysql-relay-bin.000002 | 509 | Write_rows | 1 | 388 | table_id: 108 flags: STMT_END_F | | mysql-relay-bin.000002 | 554 | Xid | 1 | 419 | COMMIT /* xid=22 */ | +------------------------+-----+----------------+-----------+-------------+---------------------------------------+ 9 rows in set (0.00 sec