Windows: log-rotate setting by config file does not work correctly

[daipom]

Describe the bug

https://docs.fluentd.org/deployment/logging#log-rotation-setting

NOTE: When --log-rotate-age is specified on Windows, log files are separated into log-supervisor-0.log, log-0.log, ..., log-N.log where N is generation - 1 due to the system limitation. Windows does not permit delete and rename files simultaneously owned by another process.

NOTE: When --log-rotate-size is specified on Windows, log files are separated into log-supervisor-0.log, log-0.log, ..., log-N.log where N is generation - 1 due to the system limitation. Windows does not permit delete and rename files simultaneously owned by another process.

As this document says, If rotation is enabled, each process must output a different log file on Windows.

However, when using log-rotate setting of system directive, the supervisor process outputs its log to log-0.log, not log-supervisor-0.log.

When using command line options such as --log-rotate-age, the following code in command/fluentd.rb fixes the path for the supervisor.

• https://github.com/fluent/fluentd/blob/v1.15.2/lib/fluent/command/fluentd.rb#L348-L356

This process seems to be missing for log-rotate setting of system directive.

To Reproduce

Just run the fluentd with the following environment and the following config.

> bundle exec fluentd -c fluentd.conf -o fluentd.log

Expected behavior

First, the following two files are created.

• fluentd-0.log
• fluentd-supervisor-0.log

Then, they will be rotated without an error.

Your Environment

- Fluentd version: 1.15.2
- TD Agent version:
- Operating system: Windows 10
- Kernel version:

Your Configuration

<system>
  <log>
    rotate_age 5
    rotate_size 2000
  </log>
</system>

<source>
  @type sample
  tag test.log
  rate 100
  dummy {"message": "This is the test message"}
</source>

<match test.**>
  @type stdout
</match>

Your Error Log

Immediately the following error begins to output to the console.

> bundle exec fluentd -c fluentd.conf -o fluentd.log
log shifting failed. Permission denied @ rb_file_s_rename - (.\fluent\fluentd-0.log, .\fluent\fluentd-0.log.0)
log writing failed. closed stream
log shifting failed. closed stream
...

Additional context

When using command line options, this problem does not occur.

> bundle exec fluentd -c fluentd.conf -o fluentd.log --log-rotate-age 5