MySQL Shell系列——升级检查器

MySQL Shell提供了一套工具集，用户可以利用这套工具集完成不同的MySQL 任务。在这一篇文章里，将为读者介绍升级检查器。

用户可以使用升级检查器来检查MySQL 5.7服务器实例，以及MySQL 8.0服务器实例与最新MySQL 8.0版本的兼容性错误和升级问题。在这里再次强调一下，使用MySQL 5.7的用户，你的MySQL该升级了。按照目前制定的产品生命周期计划，MySQL 5.7在明年10月份之后不再提供任何补丁代码，届时如果遇到安全问题，将会影响到系统的安全性。

升级检查器可以检查服务器实例的配置文件(my.cnf或my.ini)。如果存在现有的配置文件中已经定义，但在目标服务器版本中被删除的任何系统变量，或者现有的配置文件中没有定义，但在目标MySQL服务器版本中具有不同默认值的任何系统变量。升级检查器将列出相关信息。

升级检查器可以生成默认格式的输出，也可以生成JSON格式的输出，使用JSON格式可能更容易进行自动化的解析和处理。

使用该工具时，只需在MySQL Shell中执行：

util.checkForServerUpgrade (ConnectionData connectionData, Dictionary options)

注意选项部分，第一个选项用于提供连接至MySQL实例的信息，第二个选项以字典的形式提供，包括目标版本、配置路径及输出格式等内容。

举一个例子：

 MySQL  localhost:3310 ssl  JS > util.checkForServerUpgrade('root@localhost:3310',{"targetVersion":"8.0.28"})
The MySQL server at localhost:3310, version 8.0.20 - MySQL Community Server -
GPL, will now be checked for compatibility issues for upgrade to MySQL 8.0.28...

1) Issues reported by 'check table x for upgrade' command
  No issues found

Errors:   0
Warnings: 0
Notices:  0

No known compatibility errors or issues were found.

可以看到，从8.0.20升级至8.0.28是不存在不兼容现象的。

再举一个5.7的🌰：

MySQL  localhost:3306  JS > util.checkForServerUpgrade('root@localhost:3306',{"targetVersion":"8.0.28"})
Please provide the password for 'root@localhost:3306': ****
Save password for 'root@localhost:3306'? [Y]es/[N]o/Ne[v]er (default No): y
The MySQL server at localhost:3306, version 5.7.18-log - MySQL Community Server
(GPL), will now be checked for compatibility issues for upgrade to MySQL
8.0.28...

1) Usage of old temporal type
  No issues found

2) Usage of db objects with names conflicting with new reserved keywords
  No issues found

3) Usage of utf8mb3 charset
  No issues found

4) Table names in the mysql schema conflicting with new tables in 8.0
  No issues found

5) Partitioned tables using engines with non native partitioning
  No issues found

6) Foreign key constraint names longer than 64 characters
  No issues found

7) Usage of obsolete MAXDB sql_mode flag
  No issues found

8) Usage of obsolete sql_mode flags
  Notice: The following DB objects have obsolete options persisted for
    sql_mode, which will be cleared during upgrade to 8.0.
  More information:
    https://dev.mysql.com/doc/refman/8.0/en/mysql-nutshell.html#mysql-nutshell-removals

  global system variable sql_mode - defined using obsolete NO_AUTO_CREATE_USER
    option

9) ENUM/SET column definitions containing elements longer than 255 characters
  No issues found

10) Usage of partitioned tables in shared tablespaces
  No issues found

11) Circular directory references in tablespace data file paths
  No issues found

12) Usage of removed functions
  No issues found

13) Usage of removed GROUP BY ASC/DESC syntax
  No issues found

14) Removed system variables for error logging to the system log configuration
  To run this check requires full path to MySQL server configuration file to be specified at 'configPath' key of options dictionary
  More information:
    https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-13.html#mysqld-8-0-13-logging

15) Removed system variables
  To run this check requires full path to MySQL server configuration file to be specified at 'configPath' key of options dictionary
  More information:
    https://dev.mysql.com/doc/refman/8.0/en/added-deprecated-removed.html#optvars-removed

16) System variables with new default values
  To run this check requires full path to MySQL server configuration file to be specified at 'configPath' key of options dictionary
  More information:
    https://mysqlserverteam.com/new-defaults-in-mysql-8-0/

17) Zero Date, Datetime, and Timestamp values
  No issues found

18) Schema inconsistencies resulting from file removal or corruption
  No issues found

19) Tables recognized by InnoDB that belong to a different engine
  No issues found

20) Issues reported by 'check table x for upgrade' command
  No issues found

21) New default authentication plugin considerations
  Warning: The new default authentication plugin 'caching_sha2_password' offers
    more secure password hashing than previously used 'mysql_native_password'
    (and consequent improved client connection authentication). However, it also
    has compatibility implications that may affect existing MySQL installations. 
    If your MySQL installation must serve pre-8.0 clients and you encounter
    compatibility issues after upgrading, the simplest way to address those
    issues is to reconfigure the server to revert to the previous default
    authentication plugin (mysql_native_password). For example, use these lines
    in the server option file:
    
    [mysqld]
    default_authentication_plugin=mysql_native_password
    
    However, the setting should be viewed as temporary, not as a long term or
    permanent solution, because it causes new accounts created with the setting
    in effect to forego the improved authentication security.
    If you are using replication please take time to understand how the
    authentication plugin changes may impact you.
  More information:
    https://dev.mysql.com/doc/refman/8.0/en/upgrading-from-previous-series.html#upgrade-caching-sha2-password-compatibility-issues
    https://dev.mysql.com/doc/refman/8.0/en/upgrading-from-previous-series.html#upgrade-caching-sha2-password-replication

Errors:   0
Warnings: 1
Notices:  1

No fatal errors were found that would prevent an upgrade, but some potential issues were detected. Please ensure that the reported issues are not significant before upgrading.

从输出报告可以看出，升级检查器在21个方面进行了检查，最终得出一个警告信息和一个提示。

通过以上的例子，读者可以发现，MySQL Shell提供的升级检查工具能够帮助用户检测版本兼容性，减轻升级工作负担。

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