一文搞懂MySQL主从复制

1 为什么要主从复制

主从复制、读写分离一般是一起使用的。目的很简单，就是为了提高数据库的并发性能。你想，假设是单机，读写都在一台MySQL上面完成，性能肯定不高。如果有三台MySQL，一台mater只负责写操作，两台salve只负责读操作，性能就能大大提高了。

所以主从复制、读写分离就是为了数据库能支持更大的并发、提高数据库的可用性。

2 主从复制步骤

2.1 环境准备

MySQL主机：

• IP地址：10.0.0.1
• 端口号：3306
• 版本：5.5

MySQL从机：

• IP地址：10.0.0.2
• 端口号：3306
• 版本：5.5

2.2 修改配置文件

MySQL主机：

[mysqld]
log-bin=/home/mysql/binlog
server-id=1

MySQL从机：

[mysqld]
server-id=2
log-bin=/home/mysql/binlog
relay-log=/home/mysql/relaylog

2.3 在MySQL中进行操作

首先重启两个MySQL

MySQL主机：

[root@iZ2ze4m2ri7irkf6h6n8zoZ mysql]# mysql -uroot -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.5.62-log MySQL Community Server (GPL)

Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> CREATE USER ymx IDENTIFIED BY '123456';
Query OK, 0 rows affected (0.00 sec)

mysql> grant replication slave on *.* to 'ymx'@'10.0.0.2'  identified by '123456';
Query OK, 0 rows affected (0.00 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)

mysql> show master status;
+---------------+----------+--------------+------------------+
| File          | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+---------------+----------+--------------+------------------+
| binlog.000003 |      594 |              |                  |
+---------------+----------+--------------+------------------+
1 row in set (0.00 sec)

MySQL从机：

[root@iZ1608aqb7ntn9Z ~]# mysql -uroot -p 
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.5.62-log MySQL Community Server (GPL)

Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| college_work       |
| db_chat            |
| db_stu_work_mg     |
| mysql              |
| performance_schema |
| sysbooking         |
| test               |
| yn_db              |
+--------------------+
9 rows in set (0.00 sec)

mysql> change master to master_host='10.0.0.1',master_user='ymx',master_password='123456',master_port=3306,master_log_file='binlog.000003',master_log_pos=594;
Query OK, 0 rows affected (0.01 sec)file='binlog.000003',master_log_pos=594;

mysql> start slave;
Query OK, 0 rows affected (0.00 sec)

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 10.0.0.1
                  Master_User: ymx
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: binlog.000003
          Read_Master_Log_Pos: 594
               Relay_Log_File: relaylog.000002
                Relay_Log_Pos: 250
        Relay_Master_Log_File: binlog.000003
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 594
              Relay_Log_Space: 399
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 1
1 row in set (0.00 sec)

2.4 测试

MySQL主机：

mysql> create database slave_db;
Query OK, 1 row affected (0.00 sec)

mysql> use slave_db;
Database changed
mysql> show tables;
Empty set (0.00 sec)

mysql> create table user( id int(20),name varchar(200));
Query OK, 0 rows affected (0.01 sec)

mysql> show tables;
+--------------------+
| Tables_in_slave_db |
+--------------------+
| user               |
+--------------------+
1 row in set (0.00 sec)

MySQL从机：

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| college_work       |
| db_chat            |
| db_stu_work_mg     |
| mysql              |
| performance_schema |
| slave_db           |
| sysbooking         |
| test               |
| yn_db              |
+--------------------+
10 rows in set (0.00 sec)

mysql> use slave_db;
Database changed
mysql> show tables;
Empty set (0.00 sec)

mysql> show tables;
+--------------------+
| Tables_in_slave_db |
+--------------------+
| user               |
+--------------------+
1 row in set (0.00 sec)

3 MySQL主从复制原理