Enable log rotation for Fluent::Log

[ganmacs]

As the log file increases, it becomes difficult to handle the log file.
So, I want to enable the log rotation for Fluent::Log to keep log files down to a manageable size.

I'll add these command line arguments to fluentd command.

• --log-rotate-age

The number of old log files to keep, or frequency of rotation (daily, weekly or monthly). The default value is 5. it is used when you set a value to --log-rotate-size and don't set a value to --log-rotate-age.If you set 0 as a value of --log-rotate-age, the logger will do no log rotation.

• --log-rotate-size

Maximum logfile size (only applies when log-rotate-age is a number). The default value is 1M.
it is used when you set a value to --log-rotate-age and don't set a value to --log-rotate-size.

[tagomoris]

What happens when --log-rotate-age is 0?

[ganmacs]

log-rotate-age means "the number of old log files to keep".
When --log-rotate-age is 0, old log files are not created.

[tagomoris]

@ganmacs What does it mean? Which one?:

• log file will be rotated, but old log will disappear immediately
• log file will not be rotated

[ganmacs]

log file will not be rotated

This one.

Fluent::Logclass uses ServerEngine::DaemonLogger class inside and ServerEngine::DaemonLogger extends Ruby's Logger class.
This is a design by ruby's Logger class( https://github.com/ruby/ruby/blob/7b2d47132ff8ee950b0f978ab772dee868d9f1b0/lib/logger.rb#L769 )

[tagomoris]

I meant that we should tell users that the default value of --log-rotate-age=0 means "no log rotation" clearly.

[ganmacs]

I added a description about the case of --log-rotate-age=0.