Mysql的主从复制

别先生

发布于 2020-09-01 15:15:20

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发布于 2020-09-01 15:15:20

文章被收录于专栏：别先生别先生

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 respective
10 owners.
11 
12 Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
13 
14 mysql> use mysql;
15 Database changed
16 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 its
10 affiliates. Other names may be trademarks of their respective
11 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=mysql
10 # 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=2
4 # 配置日志路径
5 log-bin=mysql-bin
6 # 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: 27
12    Memory: 246.4M
13    CGroup: /system.slice/mysqld.service
14            └─93028 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid
15 
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 its
14 affiliates. Other names may be trademarks of their respective
15 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: 154
10                Relay_Log_File: k8s-node3-relay-bin.000001
11                 Relay_Log_Pos: 4
12         Relay_Master_Log_File: mysql-error.000001
13              Slave_IO_Running: No
14             Slave_SQL_Running: Yes
15               Replicate_Do_DB: biehl
16           Replicate_Ignore_DB: 
17            Replicate_Do_Table: 
18        Replicate_Ignore_Table: 
19       Replicate_Wild_Do_Table: 
20   Replicate_Wild_Ignore_Table: 
21                    Last_Errno: 0
22                    Last_Error: 
23                  Skip_Counter: 0
24           Exec_Master_Log_Pos: 154
25               Relay_Log_Space: 154
26               Until_Condition: None
27                Until_Log_File: 
28                 Until_Log_Pos: 0
29            Master_SSL_Allowed: No
30            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: NULL
36 Master_SSL_Verify_Server_Cert: No
37                 Last_IO_Errno: 1236
38                 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: 0
40                Last_SQL_Error: 
41   Replicate_Ignore_Server_Ids: 
42              Master_Server_Id: 1
43                   Master_UUID: 262f593f-746e-11e9-b769-d8c497e293c1
44              Master_Info_File: /var/lib/mysql/master.info
45                     SQL_Delay: 0
46           SQL_Remaining_Delay: NULL
47       Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
48            Master_Retry_Count: 86400
49                   Master_Bind: 
50       Last_IO_Error_Timestamp: 200731 12:25:35
51      Last_SQL_Error_Timestamp: 
52                Master_SSL_Crl: 
53            Master_SSL_Crlpath: 
54            Retrieved_Gtid_Set: 
55             Executed_Gtid_Set: 
56                 Auto_Position: 0
57          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 \G
11 *************************** 1. row ***************************
12                Slave_IO_State: Waiting for master to send event
13                   Master_Host: 192.168.0.116
14                   Master_User: root
15                   Master_Port: 3306
16                 Connect_Retry: 60
17               Master_Log_File: mysql-bin.000001
18           Read_Master_Log_Pos: 154
19                Relay_Log_File: k8s-node3-relay-bin.000003
20                 Relay_Log_Pos: 367
21         Relay_Master_Log_File: mysql-bin.000001
22              Slave_IO_Running: Yes
23             Slave_SQL_Running: Yes
24               Replicate_Do_DB: biehl
25           Replicate_Ignore_DB: 
26            Replicate_Do_Table: 
27        Replicate_Ignore_Table: 
28       Replicate_Wild_Do_Table: 
29   Replicate_Wild_Ignore_Table: 
30                    Last_Errno: 0
31                    Last_Error: 
32                  Skip_Counter: 0
33           Exec_Master_Log_Pos: 154
34               Relay_Log_Space: 578
35               Until_Condition: None
36                Until_Log_File: 
37                 Until_Log_Pos: 0
38            Master_SSL_Allowed: No
39            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: 0
45 Master_SSL_Verify_Server_Cert: No
46                 Last_IO_Errno: 0
47                 Last_IO_Error: 
48                Last_SQL_Errno: 0
49                Last_SQL_Error: 
50   Replicate_Ignore_Server_Ids: 
51              Master_Server_Id: 1
52                   Master_UUID: 262f593f-746e-11e9-b769-d8c497e293c1
53              Master_Info_File: /var/lib/mysql/master.info
54                     SQL_Delay: 0
55           SQL_Remaining_Delay: NULL
56       Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
57            Master_Retry_Count: 86400
58                   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: 0
66          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 respective
10 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。