背景

主节点上线运行了一段时间后，数据量日益增大，故需要添加slave节点来更好地支撑业务的发展。但是，此时也有一定量的用户了，所以不能把主节点停机，而是在不停机的情况下添加slave节点，具体实现方法如下：

环境

防火墙和selinux都关闭

操作步骤

1.在master上对数据库做完全备份,并且拷贝到slave节点

1.1 查看当前master上的数据库

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| db1                |
| db2                |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

1.2 使用mysqldump工具进行全库备份

[root@master01 ~]#mysqldump -p -A -F --single-transaction --master-data=1 > /backup/fullbackup_`date +%F_%T`.sql
Enter password: 
[root@master01 ~]#ll /backup/
total 832
-rw-r--r-- 1 root root 849153 Nov 29 20:22 fullbackup_2019-11-29_20:22:04.sql
[root@master01 ~]#scp -p /backup/fullbackup_2019-11-29_20\:22\:04.sql root@192.168.7.72:/data/
fullbackup_2019-11-29_20:22:04.sql                   100%  829KB  14.9MB/s   00:00

1.3 创建授权复制账号

grant replication slave on *.* to repluser@'192.168.7.%' identified by '123.com';

2.在slave节点将master节点拷贝过来的完全备份进行导入

2.1 MySQL安装过程略

2.2 将以下内容添加到my.cnf文件中，然后重新启动数据库。

[mysqld]
server-id = 2
read_only = ON  #设为只读，但是对超级用户无效。

2.3 导入并查看

[root@slave01 ~]#mysql -p < /data/fullbackup_2019-11-29_20\:22\:04.sql 
Enter password: 
[root@slave01 ~]#mysql -p -e "show databases"
Enter password: 
+--------------------+
| Database           |
+--------------------+
| information_schema |
| db1                |
| db2                |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

可以看到已经将master节点上的所有库导入成功了。

3.在slave节点执行以下命令，指定连接主服务器的信息，以进行数据同步。

3.1 找到完全备份的position信息

[root@slave01 ~]#grep '^CHANGE MASTER' /data/fullbackup_2019-11-29_20\:22\:04.sql 
CHANGE MASTER TO MASTER_LOG_FILE='mysql-bin.000003', MASTER_LOG_POS=154;

3.2 配置连接主服务的信息（从完全备份的位置之后开始复制）

[root@slave01 ~]#mysql -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 11
Server version: 5.7.28 MySQL Community Server (GPL)

Copyright (c) 2000, 2019, 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> CHANGE MASTER TO
    ->   MASTER_HOST='192.168.7.71',
    ->   MASTER_USER='repluser',
    ->   MASTER_PASSWORD='123.com',
    ->   MASTER_PORT=3306,
    ->   MASTER_LOG_FILE='mysql-bin.000003',
    ->   MASTER_LOG_POS=154;
Query OK, 0 rows affected, 2 warnings (0.01 sec)

3.3 启动slave节点，并查看同步状态。

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: 192.168.7.71
                  Master_User: repluser
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000003
          Read_Master_Log_Pos: 154
               Relay_Log_File: slave01-relay-bin.000002
                Relay_Log_Pos: 320
        Relay_Master_Log_File: mysql-bin.000003
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
...省略信息...

Slave_IO_Running和Slave_SQL_Running线程都为Yes，表示主从同步成功，至此，在线添加从库已经实现。