MySQL主从复制原理与配置详解

1、主从同步（主从复制的）的原理。

答：主从同步的核心是二进制日志文件binary log，对数据库所有的增加、修改、删除操作都会在日志表里面记录一下的。mysql主从复制是异步的，串行化的，有延迟的，并不是实时的。

第一步，master主节点将改变的数据记录在本地的二进制日志中binary log，该过程称为二进制日志事件。第二步，slave将master的binary log拷贝到自己的relay log（中继日志文件）中。第三步，中继日志事件，将数据读取到自己的数据库之中。

2、mysql集群的优点，如下所示：

1）、负载均衡。2）、失败迁移。

3、由于我的机器一台是window10安装的mysql，一台是centos7安装的mysql，所以它们的配置文件分别是windows的配置文件是my.ini，linux的配置文件是my.cnf。

首先，我需要配置一下允许远程连接我的window的mysql，如下所示：

 1 Enter password: ****** 2 Welcome to the MySQL monitor.  Commands end with ; or \g. 3 Your MySQL connection id is 3 4 Server version: 5.7.24-log MySQL Community Server (GPL) 5  6 Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved. 7  8 Oracle is a registered trademark of Oracle Corporation and/or its 9 affiliates. Other names may be trademarks of their respective10 owners.11 12 Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.13 14 mysql> use mysql;15 Database changed16 mysql> grant all privileges on *.* to 'root'@'%' identified by '123456' with grant option;17 Query OK, 0 rows affected, 1 warning (0.03 sec)18 19 mysql> flush privileges;20 Query OK, 0 rows affected (0.03 sec)21 22 mysql> select host,user from user;23 +-----------+---------------+24 | host      | user          |25 +-----------+---------------+26 | %         | root          |27 | %         | user1         |28 | localhost | mysql.session |29 | localhost | mysql.sys     |30 | localhost | root          |31 +-----------+---------------+32 5 rows in set (0.00 sec)33 34 mysql>

然后使用linux的远程连接一下window的mysql，可以连接即可，如果不可以连接，需要关闭window的防火墙。反之，开启Linux的mysql可以远程连接并关闭防火墙。

 1 [root@k8s-node3 ~]# mysql -uroot -h192.168.0.116 -p123456 2 mysql: [Warning] Using a password on the command line interface can be insecure. 3 Welcome to the MySQL monitor.  Commands end with ; or \g. 4 Your MySQL connection id is 4 5 Server version: 5.7.24-log MySQL Community Server (GPL) 6  7 Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved. 8  9 Oracle is a registered trademark of Oracle Corporation and/or its10 affiliates. Other names may be trademarks of their respective11 owners.12 13 Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.14 15 mysql> show databases;16 +

4、由于我的mysql是默认安装的，所以my.ini在这个路径下面C:\ProgramData\MySQL\MySQL Server 5.7\my.ini，根据个人需求进行配置吧，开始配置，如下所示：

 1 [mysqld] 2 # 主节点master增加唯一标识符 3 server-id=1 4 # 开始配置二进制日志文件 5 log-bin="D:/program/mysql/mysql-bin" 6 # 开始配置二进制日志错误文件 7 log-error="D:/program/mysql/mysql-error" 8 # 主从同步的时候忽略的数据库 9 binlog-ignore-db=mysql10 # 可选参数，指定主从同步的时候，同步那些数据库11 binlog-do-db=test

我上面的配置一开始配置错了，导致mysql重启起不来了。还有下面的配置和自己的配置冲突了，我这里将默认的先注释了，如下所示：

Windows中的数据库授权那台计算机中的数据库是自己的从数据库。

1 mysql> grant replication slave,reload,super on *.* to 'root'@'192.168.110.%' identified by 'root';2 Query OK, 0 rows affected, 1 warning (0.00 sec)3 4 mysql>5 mysql> flush privileges;6 Query OK, 0 rows affected (0.00 sec)7 8 mysql>9 mysql>

查看主数据库的状态，每次在做主从同步前，需要观察主机状态的最新值，需要记住File、Position的值的。命令如下所示:

1 mysql> show master status;2 +--------------------+----------+--------------+------------------+-------------------+3 | File               | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |4 +--------------------+----------+--------------+------------------+-------------------+5 | mysql-error.000001 |      154 | biehl        | mysql            |                   |6 +--------------------+----------+--------------+------------------+-------------------+7 1 row in set (0.00 sec)8 9 mysql>

如果my.ini配置正确的话，重启window的mysql之后，会在自己的指定目录D:\program\mysql生成下面三个文件，mysql-bin.000001、mysql-error.err、mysql-bin.index。

5、开始在linux的mysql配置，如下所示：

1 [mysqld]2 # 从节点slave增加唯一标识符3 server-id=24 # 配置日志路径5 log-bin=mysql-bin6 # 配置主从同步的数据库名称7 replicate-do-db=test

Linux中的数据库授权那台计算机中的数据库是自己的主数据库，由于修改了my.ini所以这里重启一下Mysql的数据库。

 1 [root@k8s-node3 ~]# systemctl restart mysqld.service  2 [root@k8s-node3 ~]# systemctl status mysqld.service  3 ● mysqld.service - MySQL Server 4    Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled) 5    Active: active (running) since Fri 2020-07-31 12:21:36 CST; 7s ago 6      Docs: man:mysqld(8) 7            http://dev.mysql.com/doc/refman/en/using-systemd.html 8   Process: 93026 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=0/SUCCESS) 9   Process: 92998 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)10  Main PID: 93028 (mysqld)11     Tasks: 2712    Memory: 246.4M13    CGroup: /system.slice/mysqld.service14            └─93028 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid15 16 Jul 31 12:21:28 k8s-node3 systemd[1]: Starting MySQL Server...17 Jul 31 12:21:36 k8s-node3 systemd[1]: Started MySQL Server.18 [root@k8s-node3 ~]# 

由于没有重启Mysql的数据库之前报错了，自己重启一下然后执行命令即可。

 1 mysql> change master to master_host='192.168.0.116',master_user='root',master_password='123456',master_port=3306,master_log_file='mysql-error.000001',master_log_pos=154 ; 2 ERROR 1794 (HY000): Slave is not configured or failed to initialize properly. You must at least set --server-id to enable either a master or a slave. Additional error messages can be found in the MySQL error log. 3 mysql> exit 4 Bye 5 [root@k8s-node3 ~]# mysql -uroot -h127.0.0.1 -p123456 6 mysql: [Warning] Using a password on the command line interface can be insecure. 7 Welcome to the MySQL monitor.  Commands end with ; or \g. 8 Your MySQL connection id is 2 9 Server version: 5.7.30-log MySQL Community Server (GPL)10 11 Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.12 13 Oracle is a registered trademark of Oracle Corporation and/or its14 affiliates. Other names may be trademarks of their respective15 owners.16 17 Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.18 19 mysql> change master to master_host='192.168.0.116',master_user='root',master_password='123456',master_port=3306,master_log_file='mysql-error.000001',master_log_pos=154 ;20 Query OK, 0 rows affected, 1 warning (0.01 sec)21 22 mysql> 

6、开启主从同步，这里在linux执行即可，如下所示：

1 mysql> start slave;2 Query OK, 0 rows affected (0.01 sec)3 4 mysql> 

然后检验是否真的执行了，检查从节点的工作状态，如下所示：

 1 mysql> show slave status \G 2 *************************** 1. row *************************** 3                Slave_IO_State:  4                   Master_Host: 192.168.0.116 5                   Master_User: root 6                   Master_Port: 3306 7                 Connect_Retry: 60 8               Master_Log_File: mysql-error.000001 9           Read_Master_Log_Pos: 15410                Relay_Log_File: k8s-node3-relay-bin.00000111                 Relay_Log_Pos: 412         Relay_Master_Log_File: mysql-error.00000113              Slave_IO_Running: No14             Slave_SQL_Running: Yes15               Replicate_Do_DB: biehl16           Replicate_Ignore_DB: 17            Replicate_Do_Table: 18        Replicate_Ignore_Table: 19       Replicate_Wild_Do_Table: 20   Replicate_Wild_Ignore_Table: 21                    Last_Errno: 022                    Last_Error: 23                  Skip_Counter: 024           Exec_Master_Log_Pos: 15425               Relay_Log_Space: 15426               Until_Condition: None27                Until_Log_File: 28                 Until_Log_Pos: 029            Master_SSL_Allowed: No30            Master_SSL_CA_File: 31            Master_SSL_CA_Path: 32               Master_SSL_Cert: 33             Master_SSL_Cipher: 34                Master_SSL_Key: 35         Seconds_Behind_Master: NULL36 Master_SSL_Verify_Server_Cert: No37                 Last_IO_Errno: 123638                 Last_IO_Error: Got fatal error 1236 from master when reading data from binary log: 'Could not find first log file name in binary log index file'39                Last_SQL_Errno: 040                Last_SQL_Error: 41   Replicate_Ignore_Server_Ids: 42              Master_Server_Id: 143                   Master_UUID: 262f593f-746e-11e9-b769-d8c497e293c144              Master_Info_File: /var/lib/mysql/master.info45                     SQL_Delay: 046           SQL_Remaining_Delay: NULL47       Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates48            Master_Retry_Count: 8640049                   Master_Bind: 50       Last_IO_Error_Timestamp: 200731 12:25:3551      Last_SQL_Error_Timestamp: 52                Master_SSL_Crl: 53            Master_SSL_Crlpath: 54            Retrieved_Gtid_Set: 55             Executed_Gtid_Set: 56                 Auto_Position: 057          Replicate_Rewrite_DB: 58                  Channel_Name: 59            Master_TLS_Version: 60 1 row in set (0.00 sec)61 62 mysql> 

主要观察这两个都是yes即可，Slave_IO_Running: No和 Slave_SQL_Running: Yes，这里如果不都是yes，看Last_IO_Error: Got fatal error 1236 from master when reading data from binary log: 'Could not find first log file name in binary log index file'报错信息。

 1 mysql> stop slave; 2 Query OK, 0 rows affected (0.00 sec) 3  4 mysql> reset slave; 5 Query OK, 0 rows affected (0.00 sec) 6  7 mysql> start slave; 8 Query OK, 0 rows affected (0.01 sec) 9 10 mysql> show slave status \G11 *************************** 1. row ***************************12                Slave_IO_State: Waiting for master to send event13                   Master_Host: 192.168.0.11614                   Master_User: root15                   Master_Port: 330616                 Connect_Retry: 6017               Master_Log_File: mysql-bin.00000118           Read_Master_Log_Pos: 15419                Relay_Log_File: k8s-node3-relay-bin.00000320                 Relay_Log_Pos: 36721         Relay_Master_Log_File: mysql-bin.00000122              Slave_IO_Running: Yes23             Slave_SQL_Running: Yes24               Replicate_Do_DB: biehl25           Replicate_Ignore_DB: 26            Replicate_Do_Table: 27        Replicate_Ignore_Table: 28       Replicate_Wild_Do_Table: 29   Replicate_Wild_Ignore_Table: 30                    Last_Errno: 031                    Last_Error: 32                  Skip_Counter: 033           Exec_Master_Log_Pos: 15434               Relay_Log_Space: 57835               Until_Condition: None36                Until_Log_File: 37                 Until_Log_Pos: 038            Master_SSL_Allowed: No39            Master_SSL_CA_File: 40            Master_SSL_CA_Path: 41               Master_SSL_Cert: 42             Master_SSL_Cipher: 43                Master_SSL_Key: 44         Seconds_Behind_Master: 045 Master_SSL_Verify_Server_Cert: No46                 Last_IO_Errno: 047                 Last_IO_Error: 48                Last_SQL_Errno: 049                Last_SQL_Error: 50   Replicate_Ignore_Server_Ids: 51              Master_Server_Id: 152                   Master_UUID: 262f593f-746e-11e9-b769-d8c497e293c153              Master_Info_File: /var/lib/mysql/master.info54                     SQL_Delay: 055           SQL_Remaining_Delay: NULL56       Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates57            Master_Retry_Count: 8640058                   Master_Bind: 59       Last_IO_Error_Timestamp: 60      Last_SQL_Error_Timestamp: 61                Master_SSL_Crl: 62            Master_SSL_Crlpath: 63            Retrieved_Gtid_Set: 64             Executed_Gtid_Set: 65                 Auto_Position: 066          Replicate_Rewrite_DB: 67                  Channel_Name: 68            Master_TLS_Version: 69 1 row in set (0.00 sec)70 71 mysql> 

如果报了主从使用了相同的server-id，需要进行检查，在主从中分别查看serverid，show variables like '%server_id%';

 1 Enter password: ****** 2 Welcome to the MySQL monitor.  Commands end with ; or \g. 3 Your MySQL connection id is 4 4 Server version: 5.7.24-log MySQL Community Server (GPL) 5  6 Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved. 7  8 Oracle is a registered trademark of Oracle Corporation and/or its 9 affiliates. Other names may be trademarks of their respective10 owners.11 12 Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.13 14 mysql> show variables like '%server_id%';15 +----------------+-------+16 | Variable_name  | Value |17 +----------------+-------+18 | server_id      | 1     |19 | server_id_bits | 32    |20 +----------------+-------+21 2 rows in set, 1 warning (0.01 sec)22 23 mysql>

然后在从节点上进行查看，如下所示：

 1 mysql> show variables like '%server_id%'; 2 +----------------+-------+ 3 | Variable_name  | Value | 4 +----------------+-------+ 5 | server_id      | 2     | 6 | server_id_bits | 32    | 7 +----------------+-------+ 8 2 rows in set (0.00 sec) 9 10 mysql> 

7、测试一下主节点和从节点是否可以同步，可以在主节点的数据表插入一条数据，观察从节点的数据库是否有数据同步，需要注意的是从节点需要创建好数据库和数据表的，不然总是报一些莫名其妙的错误。在主节点添加数据，可以发现从节点已经新增数据了。

可以测试修改，删除操作，发现都是可以正常执行的。