mysqlcluster: innodb_log_file_size auto config. #501

[acekingke]

What type of PR is this?

/enhancement

Which issue(s) this PR fixes?

Fixes #501

What this PR does?

Summary:

1. When the redo log file size is not set manually, auto set redo log file size is 25% of innodb_buffer_pool_size , but never over 8G.
2. when users want set over 8G, they should set it in yaml file manually.

Special notes for your reviewer?

[runkecheng]

add unit test?

[zhl003]

You can refer to the following https://dev.mysql.com/doc/refman/8.0/en/innodb-dedicated-server.html

Perhaps we can set these size flowing below:

• innodb_log_file_size

  As of MySQL 8.0.14, log file size is configured according to the automatically configured buffer pool size.

  Table 15.9 Automatically Configured Log File Size

  Buffer Pool Size	Log File Size
  Less than 8GB	512MiB
  8GB to 128GB	1024MiB
  Greater than 128GB	2048MiB

and all this parameters can be set defalut according to innodb_dedicated_server ：

• innodb_buffer_pool_size

• innodb_log_file_size

• innodb_log_files_in_group (as of MySQL 8.0.14)

• innodb_flush_method

You can refer to the following https://dev.mysql.com/doc/refman/8.0/en/innodb-dedicated-server.html Perhaps we can set these size flowing below:

• [innodb_log_file_size](https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_log_file_size)

  As of MySQL 8.0.14, log file size is configured according to the automatically configured buffer pool size.

  Table 15.9 Automatically Configured Log File Size

  Buffer Pool Size	Log File Size
  Less than 8GB	512MiB
  8GB to 128GB	1024MiB
  Greater than 128GB	2048MiB

and all this parameters can be set defalut according to [innodb_dedicated_server](https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_dedicated_server) ：

• [innodb_buffer_pool_size](https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_buffer_pool_size)
• [innodb_log_file_size](https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_log_file_size)
• [innodb_log_files_in_group](https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_log_files_in_group) (as of MySQL 8.0.14)
• [innodb_flush_method](https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_flush_method)

[zhl003]

LGTM