see also https://gist.github.com/blowmage/4f0b1420236a1cb4a97f2ba02da2d826

logging_with_labels.rb

Google::Cloud::Logging::Logger.class_eval do
  %i{ debug info warn error }.each do |level|

    old = instance_method level
    define_method level do |message, entry_labels = {}, &block|
      logger_labels = @labels if @labels
      begin
        @labels = (@labels || {}).merge entry_labels
        old.bind(self).(message, &block)
      ensure
        @labels = logger_labels
      end
    end

  end
end