概述
MySQL8.0自2016年发布，距今已有四年，经过这四年的迭代更新，新版本的MySQL已经在逐渐向Oracle靠拢，这是一个长期的过程，也是必将是一个明确的结果。
新特性介绍
在MySQL的8.0.17版本中，MySQL首次提供了物理备份的手段，是以plugin方式提供的，该plugin是可选安装的。
clone plugin可以从本地或远程MySQL实例中clone数据。这些clone数据是一个物理快照，其中包含了innodb的schema、tables、tablespace、data dictionary信息。实际上是一个整体的数据目录。
部署
MySQL提供的插件都位于plugin_dir系统变量的目录中，默认位于base_dir/lib/plugin的目录中:
[root@master plugin]# ll -lih|grep mysql_clone.so
936927 -rwxr-xr-x. 1 mysql mysql 2.6M 9月 20 2019 mysql_clone.so
[root@master plugin]#
安装clone插件的方式非常简单，和半同步复制的插件安装一样，只要进入mysql命令行就可以：
[root@master plugin]# mysql -uroot -pxxxxxx
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 25
Server version: 8.0.18 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> INSTALL PLUGIN clone SONAME 'mysql_clone.so';
Query OK, 0 rows affected (1.57 sec)
mysql>
验证一下是否安装成功并可用：
[root@master plugin]# mysql -uroot -pxxxxxx
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 26
Server version: 8.0.18 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> SELECT PLUGIN_NAME, PLUGIN_STATUS FROM INFORMATION_SCHEMA.PLUGINS WHERE PLUGIN_NAME = 'clone';
+-------------+---------------+
| PLUGIN_NAME | PLUGIN_STATUS |
+-------------+---------------+
| clone | ACTIVE |
+-------------+---------------+
1 row in set (0.32 sec)
mysql>
使用
clone插件有两种模式：第一种为本地克隆，第二种为远程克隆。我们先来说第一种。
本地克隆
本地克隆就是在一台实例的MySQL上进行克隆备份操作。从实例目录克隆到另一个目录下。
要使用clone插件进行克隆数据，前提是必须要授权一个带有BACKUP_ADMIN权限的账号：
[root@master plugin]# mysql -uroot -pxxxxxx
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 27
Server version: 8.0.18 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> select user,host from mysql.user;
+------------------+--------------+
| user | host |
+------------------+--------------+
| root | 172.16.150.% |
| clone_user | 172.16.150.% |
| replica | 172.16.150.% |
| mysql.infoschema | localhost |
| mysql.session | localhost |
| mysql.sys | localhost |
| root | localhost |
+------------------+--------------+
9 rows in set (0.17 sec)
mysql> show grants for clone_user@'172.16.150.%';
+----------------------------------------------------------------------+
| Grants for clone_user@172.16.150.% |
+----------------------------------------------------------------------+
| GRANT USAGE ON *.* TO `clone_user`@`172.16.150.%` |
| GRANT BACKUP_ADMIN ON *.* TO `clone_user`@`172.16.150.%` |
+----------------------------------------------------------------------+
2 rows in set (0.15 sec)
mysql>
在服务器上新建一个备份目录，并授权给mysql用户(必须)：
[root@master ~]# mkdir -p /backup/mysql
[root@master backup]# ll -lih / | grep backup
17451147 drwxr-xr-x. 3 root root 19 8月 26 06:30 backup
[root@master backup]#
[root@master backup]# chown -R mysql:mysql /backup/mysql/
[root@master backup]# ll
总用量 0
drwxr-xr-x. 2 mysql mysql 6 8月 26 06:30 mysql
[root@master backup]#
进入mysql命令行，执行本地克隆命令操作：
[root@master plugin]# mysql -uroot -pxxxxxx
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 27
Server version: 8.0.18 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> CLONE LOCAL DATA DIRECTORY = '/backup/mysql/mysql_backup_2020-08-26';
Query OK, 0 rows affected (1.73 sec)
mysql>
这里要注意的是：克隆目录/backup/mysql/mysql_backup_2020-08-26，mysql_backup_2020-08-26 该目录不能存在，否则会报错：
ERROR 1007 (HY000): Can't create database '/backup/mysql'; database exists
远程克隆
远程克隆，功能是从远程的MySQL实例上用克隆插件克隆数据后，传输到本地的MySQL实例上。
同样的，在进行远程克隆之前，也一样需要有权限克隆的账号，在远程的MySQL上，需要有BACKUP_ADMIN权限的账号。
在接收数据的MySQL上需要有CLONE_ADMIN权限的账号。
上面在本地克隆的操作中已经建立了远程的BACKUP_ADMIN权限的账号。
[root@master plugin]# mysql -uroot -pxxxxxx
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 28
Server version: 8.0.18 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> show grants for clone_user@'172.16.150.%';
+----------------------------------------------------------------------+
| Grants for clone_user@172.16.150.% |
+----------------------------------------------------------------------+
| GRANT USAGE ON *.* TO `clone_user`@`172.16.150.%` |
| GRANT CLONE_ADMIN ON *.* TO `clone_user`@`172.16.150.%` |
+----------------------------------------------------------------------+
2 rows in set (0.14 sec)
mysql>
我们来尝试克隆一次远程MySQL实例的数据：
#先创建好要存放克隆到本地的数据目录
[root@slave ~]# tree /backup/
/backup/
0 directories, 0 files
#这里要先指定远程实例的地址，使用clone_valid_donor_list参数
[root@master plugin]# mysql -uroot -pxxxxxx
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 28
Server version: 8.0.18 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> SET GLOBAL clone_valid_donor_list = '10.211.55.5:12309';
#使用clone_user登陆本机MySQL，开始克隆远程实例上的数据到/backup/mysql/目录下，注意/backup下的mysql目录不能存在，且/backup目录必须要有mysql读取和写入权限。
[root@slave ~]# mysql -uclone_user -p123456 -h10.211.55.6 -P12309
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 39
Server version: 8.0.18 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> CLONE INSTANCE FROM 'clone_user'@'10.211.55.5':12309 IDENTIFIED BY '123456' DATA DIRECTORY = '/backup/mysql';
ERROR 1006 (HY000): Can't create database '/backup/mysql/' (errno: 13 - Permission denied)
mysql> \q
Bye
[root@slave ~]# chown -R mysql:mysql /backup/
[root@slave ~]# mysql -uclone_user -p123456 -h10.211.55.6 -P12309
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 40
Server version: 8.0.18 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> CLONE INSTANCE FROM 'clone_user'@'10.211.55.5':12309 IDENTIFIED BY '123456' DATA DIRECTORY = '/backup/mysql';
Query OK, 0 rows affected (2.13 sec)
mysql> \q
Bye
[root@slave ~]# ls /backup/mysql/
#clone ib_buffer_pool ibdata1 ib_logfile0 ib_logfile1 meta mysql mysql.ibd sys test undo_001 undo_002
[root@slave ~]#
远程克隆语句的语法：
CLONE INSTANCE FROM 'user'@'host':port
IDENTIFIED BY 'password'
[DATA DIRECTORY [=] 'clone_dir']
[REQUIRE [NO] SSL];
user:远程实例上有克隆权限的用户
host:远程实例的IP或域名
port:远程实例的端口号
password:远程实例上克隆用户的密码
[DATA DIRECTORY [=] 'clone_dir']:可以选择克隆到本地哪个目录，注意克隆到的目录不能存在，路径需要存在。如果不写的话，默认是当前datadir目录。
[REQUIRE [NO] SSL]:是否使用SSL进行传输
相关系统变量
[root@slave mysql]# mysql -uroot -pxxxxxx
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.18 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> show variables like 'clone_%';
+-----------------------------+---------+
| Variable_name | Value |
+-----------------------------+---------+
| clone_autotune_concurrency | ON |
| clone_buffer_size | 4194304 |
| clone_ddl_timeout | 300 |
| clone_enable_compression | OFF |
| clone_max_concurrency | 16 |
| clone_max_data_bandwidth | 0 |
| clone_max_network_bandwidth | 0 |
| clone_ssl_ca | |
| clone_ssl_cert | |
| clone_ssl_key | |
| clone_valid_donor_list | |
+-----------------------------+---------+
11 rows in set (0.34 sec)
mysql>
有关clone插件的系统变量都是以clone_开头的变量，下面来简单介绍一下说明：
clone_autotune_concurrency:默认为ON，用于在远程克隆操作时，额外生成动态线程，以优化传输速度。仅适用于接收实例。 clone_max_concurrency:定义远程克隆操作时，动态生成的线程的最大限制。和上面的参数有关。 clone_buffer_size:仅适用于本地克隆操作，定义在数据传输期间使用的缓冲期大小。默认为4M，较大的缓冲区可能会提高性能。 clone_ddl_timeout:定义在克隆操作时，等待备份锁定的超时时间，单位为秒，适用于接收和远程MySQL实例。需要注意的是，克隆操作不能与DDL操作同时进行。且克隆操作会上一个备份锁。设置为0时，如果有同时的DDL操作，那么克隆将会立即失败。 clone_enable_compression:仅适用于接收实例。该参数定义在远程克隆期间是否开启网络层的数据压缩，以节省带宽，提高传输速率。 clone_max_data_bandwidth:定义远程克隆操作的单个线程最大传输速率，以每秒(MB)为单位。如果有4个线程，那么总的传输速率就是每秒4MB。设置为0表示无限制。 clone_max_network_bandwidth:定义远程克隆操作的最大网络传输速率，同样以每秒(MB)为单位。该参数仅适用于接收实例。 clone_valid_donor_list:在远程克隆操作时，定义的远程实例地址，仅在接收实例上设置。 其他均为SSL相关参数。
写在最后
MySQL8.0版本带来了非常多的新特性，但是很多小坑也是新的东西带来的。clone插件可以近似看作一次物理备份，只不过这个备份的限制是比较大的。
首先，备份锁的存在，就决定了在克隆操作时，不能在业务期间做。
其次，需要注意的是克隆路径中，目标目录是一定不能存在的，要mysql自己创建，否则会报错
最后，clone提供了控制网络和IO速率、线程数和设置缓冲区的参数，这一点可能在备份过程中起到非常好的限制效果。
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