If the RAILS_DEFAULT_LOGGER constant is already set, this initialization routine does nothing. If the constant is not set, and Configuration#logger is not nil, this also does nothing. Otherwise, a new logger instance is created at Configuration#log_path, with a default log level of Configuration#log_level.

If the log could not be created, the log will be set to output to STDERR, with a log level of WARN.

Source Code

# File initializer.rb, line 247
def initialize_logger
  # if the environment has explicitly defined a logger, use it
  return if defined?(RAILS_DEFAULT_LOGGER)

  unless logger = configuration.logger
    begin
      logger = ActiveSupport::BufferedLogger.new(configuration.log_path)
      logger.level = ActiveSupport::BufferedLogger.const_get(configuration.log_level.to_s.upcase)
      if configuration.environment == "production"
        logger.auto_flushing = false
        logger.set_non_blocking_io
      end
    rescue StandardError =>e
      logger = ActiveSupport::BufferedLogger.new(STDERR)
      logger.level = ActiveSupport::BufferedLogger::WARN
      logger.warn(
        "Rails Error: Unable to access log file. Please ensure that #{configuration.log_path} exists and is chmod 0666. " +
        "The log level has been raised to WARN and the output directed to STDERR until the problem is fixed."
      )
    end
  end

  silence_warnings { Object.const_set "RAILS_DEFAULT_LOGGER", logger }
end