mysql主从

1. 主从简介

在现代企业中,数据显得尤为重要,而存储数据的数据库选择又五花八门,但无论是何种数据库,均存在着一种隐患。

想几个问题:

  • 用一台数据库存放数据,若此数据库服务器宕机了导致数据丢失怎么办?
  • 业务量大了,数据多了,访问的人多了,一台数据库无法保证服务质量了怎么办?

1.1 主从作用

  • 实时灾备,用于故障切换
  • 读写分离,提供查询服务
  • 备份,避免影响业务

1.2 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
  • 联级复制

2. 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

3. 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:

3.1 mysql安装

分别在主从两台服务器上安装mysql-5.7版本,此处略过安装步骤,若有疑问请参考《mysql基础》与《mysql进阶》两篇文章。

3.2 mysql主从配置

3.2.1 确保从数据库与主数据库里的数据一样

为确保从数据库与主数据库里的数据一样,先全备主数据库并还原到从数据库中

//先查看主库有哪些库
[root@localhost ~]# mysql -uroot -pwangqing123! -e 'show databases;'
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| student            |
| sys                |
| teacher            |
+--------------------+

//再查看从库有哪些库
[root@localhost ~]# mysql -uroot -pwangqing123! -e 'show databases;'
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+


//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
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

//备份主库并将备份文件传送到从库
[root@localhost ~]# mysqldump -uroot -pwangqing123! --all-databases > /opt/all-201808191200.sql
mysqldump: [Warning] Using a password on the command line interface can be insecure.
[root@localhost ~]# ls /opt/
all-201808191200.sql
[root@localhost ~]# scp /opt/all-201808191200.sql root@172.16.12.129:/opt/
root@172.16.12.129's password:
all-201808191200.sql                              100%  786KB  10.6MB/s   00:00 

//解除主库的锁表状态,直接退出交互式界面即可
mysql> quit
Bye


//在从库上恢复主库的备份并查看从库有哪些库,确保与主库一致
[root@localhost ~]# mysql -uroot -pwangqing123! < /opt/all-201808191200.sql
mysql: [Warning] Using a password on the command line interface can be insecure.
[root@localhost ~]# mysql -uroot -pwangqing123! -e 'show databases;'
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| student            |
| sys                |
| teacher            |
+--------------------+

3.2.2 在主数据库里创建一个同步账号授权给从数据库使用

mysql> CREATE USER 'repl'@'172.16.12.129' IDENTIFIED BY 'repl123';
Query OK, 0 rows affected (0.00 sec)

mysql> GRANT REPLICATION SLAVE ON *.* TO 'repl'@'172.16.12.129';
Query OK, 0 rows affected (0.00 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

3.2.3 配置主数据库

[root@localhost ~]# vim /etc/my.cnf
//在[mysqld]这段的后面加上如下内容
[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值必须比从库的大

symbolic-links=0

log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid 


//重启mysql服务
[root@localhost ~]# systemctl restart mysqld
[root@localhost ~]# ss -antl
State       Recv-Q Send-Q      Local Address:Port                     Peer Address:Port
LISTEN      0      128                     *:22                                  *:*
LISTEN      0      100             127.0.0.1:25                                  *:*
LISTEN      0      128                    :::22                                 :::*
LISTEN      0      100                   ::1:25                                 :::*
LISTEN      0      80                     :::3306                               :::* 


//查看主库的状态
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000001 |      154 |              |                  |                   |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.01 sec)

3.2.4 配置从数据库

[root@localhost ~]# vim /etc/my.cnf
//添加如下内容
[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值必须小于主库的该值
relay-log=mysql-relay-bin       //启用中继日志relay-log

symbolic-links=0

log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid


//重启从库的mysql服务
[root@localhost ~]# systemctl restart mysqld
[root@localhost ~]# ss -antl
State      Recv-Q Send-Q           Local Address:Port                          Peer Address:Port
LISTEN     0      128                          *:22                                       *:*
LISTEN     0      100                  127.0.0.1:25                                       *:*
LISTEN     0      128                         :::22                                      :::*
LISTEN     0      100                        ::1:25                                      :::*
LISTEN     0      80                          :::3306                                    :::*




//配置并启动主从复制
mysql> CHANGE MASTER TO
    -> MASTER_HOST='172.16.12.128',
    -> MASTER_USER='repl',
    -> MASTER_PASSWORD='repl123',
    -> MASTER_LOG_FILE='mysql-bin.000001',
    -> MASTER_LOG_POS=154;
Query OK, 0 rows affected, 2 warnings (0.33 sec)

mysql> start slave;
Query OK, 0 rows affected (0.01 sec)


//查看从服务器状态
mysql> show slave status \G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 172.16.12.128
                  Master_User: repl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000001
          Read_Master_Log_Pos: 154
               Relay_Log_File: mysql-relay-bin.000002
                Relay_Log_Pos: 320
        Relay_Master_Log_File: mysql-bin.000001
             Slave_IO_Running: Yes      //此处必须为Yes
            Slave_SQL_Running: Yes      //此处必须为Yes
              Replicate_Do_DB:
          Replicate_Ignore_DB:  

3.2.5 测试验证

在主服务器的student库的bj2表中插入数据:

mysql> select * from bj2;
Empty set (0.00 sec)

mysql> insert into bj2 values (1,'sean',20),(2,'tom',23),(3,'jerry',30);
Query OK, 3 rows affected (0.00 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> select * from bj2;
+----+-------+------+
| id | name  | age  |
+----+-------+------+
|  1 | sean  |   20 |
|  2 | tom   |   23 |
|  3 | jerry |   30 |
+----+-------+------+
3 rows in set (0.00 sec)

在从数据库中查看数据是否同步:

mysql> use student;
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 bj2;
+----+-------+------+
| id | name  | age  |
+----+-------+------+
|  1 | sean  |   20 |
|  2 | tom   |   23 |
|  3 | jerry |   30 |
+----+-------+------+
3 rows in set (0.00 sec)

作业

1.mysql主从配置原理手抄10遍
2.配置mysql主从复制
3.写博客