主从介绍

MySQL主从又叫做Replication、AB复制。简单讲就是A和B两台机器做主从后，在A上写数据，另外一台B也会跟着写数据，两者数据实时同步的。
MySQL主从是基于binlog的，主上须开启binlog才能进行主从。
主从过程大致有3个步骤：
1）主将更改操作记录到binlog里
2）从将主的binlog事件(sql语句)同步到从本机上并记录在relaylog里中继日志
3）从根据relaylog里面的sql语句按顺序执行
MySQL主从配置 - 图1

  • 主服务器上有一个log dump线程，用来和从的I/O线程传递binlog；
  • 从服务器上有两个线程，其中I/O线程用来同步主的binlog并生成relaylog，另外一个SQL线程用来把relaylog里面的sql语句落地。

    使用场景

    1、数据的备份。
    单纯的读。当主服务器损坏，从服务器可以顶替
    2、主从同时被使用
    当主的服务器压力过大，从节点也被用来读数据。

    配置

    准备

    | 主机名 | IP | MySQL版本 | centos版本 | | —- | —- | —- | —- | | server | 192.168.100.10 | mysql-5.6.47-linux-glibc2.12-x86_64.tar.gz | centos7.2-1511 | | client | 192.168.100.20 | | |

两台虚拟机均安装完成二进制免编译MySQL，关闭防火墙
参考：https://www.yuque.com/docs/share/525f338c-a471-4aa3-be85-da0f6d3919da?# 《二进制免编译安装MySQL》

过程

主节点操作

  1. # .err结尾的文件为错误日志
  2. [root@server ~]# ls -a /data/mysql/
  3. .         ibdata1      localhost.localdomain.err  server.err
  4. ..        ib_logfile0  mysql                      server.pid
  5. auto.cnf  ib_logfile1  performance_schema         test
  6. [root@server ~]# 
  7. # 修改配置文件 /etc/my.cnf  确定有log_bin 和server_id
  8. [root@server ~]# vim /etc/my.cnf
  9. log_bin=sxb
  10. server_id = 41
  11. [root@server ~]# service mysqld restart 
  12. Shutting down MySQL.. SUCCESS! 
  13. Starting MySQL. SUCCESS! 
  14. # 可以看到多出log_bin名为开头的两个文件，sxb.000001、sxb.index
  15. # 这两个文件为bin_log文件和索引文件 可以参考流程图
  16. [root@server ~]# ls -a /data/mysql/
  17. .         ibdata1      localhost.localdomain.err  server.err  sxb.index
  18. ..        ib_logfile0  mysql                      server.pid  test
  19. auto.cnf  ib_logfile1  performance_schema         sxb.000001
  20. [root@server ~]# 
  23. # 创建主从用户 权限
  24. [root@server ~]# mysql -uroot -p12456
  25. Warning: Using a password on the command line interface can be insecure.
  26. ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
  27. [root@server ~]# mysql -uroot -p123456
  28. Warning: Using a password on the command line interface can be insecure.
  29. Welcome to the MySQL monitor.  Commands end with ; or \g.
  30. Your MySQL connection id is 2
  31. Server version: 5.6.47-log MySQL Community Server (GPL)
  33. Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
  35. Oracle is a registered trademark of Oracle Corporation and/or its
  36. affiliates. Other names may be trademarks of their respective
  37. owners.
  39. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
  41. mysql> 
  43. # 创建主从用户 权限
  44. mysql> grant replication slave on *.* to 'repl'@192.168.100.20 identified by '123456'; 
  45. Query OK, 0 rows affected (0.00 sec)
  47. # 刷新权限
  48. mysql> flush privileges;
  49. Query OK, 0 rows affected (0.00 sec)
  51. # 查看server节点状态
  52. mysql> show master status ;
  53. +------------+----------+--------------+------------------+-------------------+
  54. | File       | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
  55. +------------+----------+--------------+------------------+-------------------+
  56. | sxb.000001 |      410 |              |                  |                   |
  57. +------------+----------+--------------+------------------+-------------------+
  58. 1 row in set (0.00 sec)
  60. mysql>

从节点配置

  1. # 从节点修改配置文件，确保有server_id 这个字段，
  2. # 字段id不要一样，一般以ip最后一位结尾
  3. [root@client ~]# vim /etc/my.cnf
  4. server_id = 42
  5. mysql> stop slave;
  6. Query OK, 0 rows affected, 1 warning (0.00 sec)
  8. # 创建连接， 主节点信息，bin_log文件名及大小
  10. mysql> change master to master_host='192.168.100.10',master_user='repl',master_password='123456',master_log_file='sxb.000001',master_log_pos=410;
  11. Query OK, 0 rows affected, 2 warnings (0.01 sec)
  13. mysql> 
  14. mysql> start slave;
  15. Query OK, 0 rows affected (0.00 sec)
  17. mysql> 
  18. mysql> show slave status\G;
  19. *************************** 1. row ***************************
  20.                Slave_IO_State: Waiting for master to send event
  21.                   Master_Host: 192.168.100.10
  22.                   Master_User: repl
  23.                   Master_Port: 3306
  24.                 Connect_Retry: 60
  25.               Master_Log_File: sxb.000002
  26.           Read_Master_Log_Pos: 120
  27.                Relay_Log_File: server-relay-bin.000004
  28.                 Relay_Log_Pos: 277
  29.         Relay_Master_Log_File: sxb.000002
  30.              Slave_IO_Running: Yes
  31.             Slave_SQL_Running: Yes
  32.               Replicate_Do_DB: 
  33.           Replicate_Ignore_DB: 
  34.            Replicate_Do_Table: 
  35.        Replicate_Ignore_Table: 
  36.       Replicate_Wild_Do_Table: 
  37.   Replicate_Wild_Ignore_Table: 
  38.                    Last_Errno: 0
  39.                    Last_Error: 
  40.                  Skip_Counter: 0
  41.           Exec_Master_Log_Pos: 120
  42.               Relay_Log_Space: 608
  43.               Until_Condition: None
  44.                Until_Log_File: 
  45.                 Until_Log_Pos: 0
  46.            Master_SSL_Allowed: No
  47.            Master_SSL_CA_File: 
  48.            Master_SSL_CA_Path: 
  49.               Master_SSL_Cert: 
  50.             Master_SSL_Cipher: 
  51.                Master_SSL_Key: 
  52.         Seconds_Behind_Master: 0
  53. Master_SSL_Verify_Server_Cert: No
  54.                 Last_IO_Errno: 0
  55.                 Last_IO_Error: 
  56.                Last_SQL_Errno: 0
  57.                Last_SQL_Error: 
  58.   Replicate_Ignore_Server_Ids: 
  59.              Master_Server_Id: 29
  60.                   Master_UUID: 797e5ab1-1508-11ec-bc02-000c29df5533
  61.              Master_Info_File: /data/mysql/master.info
  62.                     SQL_Delay: 0
  63.           SQL_Remaining_Delay: NULL
  64.       Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it
  65.            Master_Retry_Count: 86400
  66.                   Master_Bind: 
  67.       Last_IO_Error_Timestamp: 
  68.      Last_SQL_Error_Timestamp: 
  69.                Master_SSL_Crl: 
  70.            Master_SSL_Crlpath: 
  71.            Retrieved_Gtid_Set: 
  72.             Executed_Gtid_Set: 
  73.                 Auto_Position: 0
  74. 1 row in set (0.00 sec)
  76. ERROR: 
  77. No query specified
  79. mysql>

测试

  1. # 主节点创建一个库，测试操作在这个库进行
  2. mysql> show databases;
  3. +--------------------+
  4. | Database           |
  5. +--------------------+
  6. | information_schema |
  7. | mysql              |
  8. | performance_schema |
  9. | test               |
  10. +--------------------+
  11. 4 rows in set (0.00 sec)
  13. mysql> create database sxb;
  14. Query OK, 1 row affected (0.00 sec)
  16. mysql> show databases;
  17. +--------------------+
  18. | Database           |
  19. +--------------------+
  20. | information_schema |
  21. | mysql              |
  22. | performance_schema |
  23. | sxb                |
  24. | test               |
  25. +--------------------+
  26. 5 rows in set (0.00 sec)
  28. mysql> 
  31. # 从节点查看同步信息
  32. mysql> show databases;
  33. +--------------------+
  34. | Database           |
  35. +--------------------+
  36. | information_schema |
  37. | mysql              |
  38. | performance_schema |
  39. | sxb                |
  40. | test               |
  41. +--------------------+
  42. 5 rows in set (0.01 sec)
  44. mysql> 
  46. # 000001文件大小为主节点操作命令组成
  47. # 可以通过bin_log文件恢复数据

注意

1、不要在从节点对数据库进行写入删除操作

拓展

读写分离
分库分表
不停机进行主从