Test: Some tests overwrite the global logger for tests

[daipom]

Describe the bug

Fluentd prepares a global logger with DummyLogDevice for tests.

fluentd/test/helper.rb

Lines 151 to 155 in bf7498d

	dl_opts = {}
	dl_opts[:log_level] = ServerEngine::DaemonLogger::WARN
	logdev = Fluent::Test::DummyLogDevice.new
	logger = ServerEngine::DaemonLogger.new(logdev, dl_opts)
	$log ||= Fluent::Log.new(logger)

However, some tests overwrite this global logger.

• fluentd/test/test_logger_initializer.rb

  Line 23 in bf7498d

  logger.init(:supervisor, 0)

• fluentd/test/test_supervisor.rb

  Lines 862 to 876 in bf7498d

  	def create_debug_dummy_logger
  	dl_opts = {}
  	dl_opts[:log_level] = ServerEngine::DaemonLogger::DEBUG
  	logdev = Fluent::Test::DummyLogDevice.new
  	logger = ServerEngine::DaemonLogger.new(logdev, dl_opts)
  	$log = Fluent::Log.new(logger)
  	end
  	def create_info_dummy_logger
  	dl_opts = {}
  	dl_opts[:log_level] = ServerEngine::DaemonLogger::INFO
  	logdev = Fluent::Test::DummyLogDevice.new
  	logger = ServerEngine::DaemonLogger.new(logdev, dl_opts)
  	$log = Fluent::Log.new(logger)
  	end

• fluentd/test/test_supervisor.rb

  Lines 727 to 731 in bf7498d

  	sv = Fluent::Supervisor.new(opts)
  	log = sv.instance_variable_get(:@log)
  	log.init(:standalone, 0)
  	assert_equal Fluent::LogDeviceIO, $log.out.class

Is this as intended?
Is this affecting other tests depending on the test order?

I was trying to fix test_logger_initializer in the following PR, and I found this test may affect other tests.

• Windows: Fix a bug that the wrong log file is reopened with log rotate setting when flushing or graceful reloading #4054

I thought I needed to make sure the logger on the global was not changed, but when I looked into it, other tests are also overwriting the logger on the global, so I am not sure what is correct...

-> This can cause unintended behavior depending on the test order, so we should fix this.

To Reproduce

None

Expected behavior

None

Your Environment

None

Your Configuration

None

Your Error Log

None

Additional context

No response

[daipom]

I just understood.

fluentd/lib/fluent/test.rb

Lines 38 to 41 in bf7498d

	def self.setup
	ENV['SERVERENGINE_WORKER_ID'] = '0'
	$log = dummy_logger

Plugin tests uses Fluentd::Test.setup() and this initializes $log.
This recovers some tests' overwriting, so the current tests work correctly.

However, this can cause problems depending on the test order, and we should fix this.

[daipom]

I reopened this since we have to fix this.

I think we should fix some tests, but we should also fix LoggerInitializer.

fluentd/lib/fluent/supervisor.rb

Line 591 in bf7498d

$log = Fluent::Log.new(logger, @opts)

I think LoggerInitializer::init() should not overwrite $log directly.

I wonder if there was a reason for this...

[daipom]

Possibly there are other areas where the global logger is overwritten.
If we find it, we should fix it.