Logger: Fails to launch Fluentd without specifying the path in the command line options on Windows with rotation

[daipom]

Describe the bug

If you enable log rotation and don't specify the log path, then Fluentd fails to start.

• Windows only
• Since v1.16.0
  • This is a bug of Fix logger initialization #4091

nil check for @log_path to be passed to Fluent::Log.per_process_path() is missing:

fluentd/lib/fluent/supervisor.rb

Lines 696 to 705 in dc7e4b2

	rotate = @log_rotate_age || @log_rotate_size
	actual_log_path = @log_path
	# We need to prepare a unique path for each worker since Windows locks files.
	if Fluent.windows? && rotate
	actual_log_path = Fluent::Log.per_process_path(@log_path, process_type, worker_id)
	end
	if actual_log_path && actual_log_path != "-"
	FileUtils.mkdir_p(File.dirname(actual_log_path)) unless File.exist?(actual_log_path)

To Reproduce

Launch Fluentd with the config below, which enables rotation.

$ bundle exec fluentd -c fluent.conf
#=> The error below occurs.

---

If you specify the log path, this issue doesn't occur.

$ bundle exec fluentd -c fluent.conf -o fluent.log
#=> Fluentd starts correctly.

If the config doesn't have rotation options, this issue doesn't occur either.

Expected behavior

If rotation is enabled but the log file path is not specified,
the rotation setting is ignored, and Fluentd normally starts with output to standard output as before v1.16.0.

Your Environment

- Fluentd version: 1.16.1
- Operating system: Windows Home 10
- Kernel version: 3.1.7-340.x86_64

Your Configuration

<system>
  <log>
    rotate_age 5
  </log>
</system>

<source>
  @type sample
  tag test
</source>

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

Your Error Log

C:/Users/reang/Documents/work/fluentd/fluentd/lib/fluent/log.rb:77:in `initialize': no implicit conversion of nil into String (TypeError)

      path = Pathname(path)
                      ^^^^
        from C:/Users/reang/Documents/work/fluentd/fluentd/lib/fluent/log.rb:77:in `Pathname'
        from C:/Users/reang/Documents/work/fluentd/fluentd/lib/fluent/log.rb:77:in `per_process_path'
        from C:/Users/reang/Documents/work/fluentd/fluentd/lib/fluent/supervisor.rb:701:in `setup_global_logger'
        from C:/Users/reang/Documents/work/fluentd/fluentd/lib/fluent/supervisor.rb:624:in `configure'
        from C:/Users/reang/Documents/work/fluentd/fluentd/lib/fluent/command/fluentd.rb:351:in `<top (required)>'
        from <internal:C:/Ruby32-x64/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:37:in `require'
        from <internal:C:/Ruby32-x64/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:37:in `require'
        from C:/Users/reang/Documents/work/fluentd/fluentd/bin/fluentd:15:in `<top (required)>'
        from C:/Ruby32-x64/lib/ruby/gems/3.2.0/bin/fluentd:25:in `load'
        from C:/Ruby32-x64/lib/ruby/gems/3.2.0/bin/fluentd:25:in `<main>'

Additional context

No response

[daipom]

There was a nil check for per_process_path on v1.15.3:

fluentd/lib/fluent/supervisor.rb

Lines 550 to 566 in e89092c

	if @path && @path != "-"
	unless File.exist?(@path)
	FileUtils.mkdir_p(File.dirname(@path))
	end
	if @log_rotate_age || @log_rotate_size
	# We need to prepare a unique path for each worker since
	# Windows locks files.
	if Fluent.windows?
	path = LoggerInitializer.per_process_path(@path, process_type, worker_id)
	else
	path = @path
	end
	@logdev = Fluent::LogDeviceIO.new(path, shift_age: @log_rotate_age, shift_size: @log_rotate_size)
	else
	@logdev = File.open(@path, "a")
	end