Rails.logger is the best solution,one more think i want to add,if you want separate log file you could use like this
def read(args)
unless args.blank?
cache_key= self.get_cache_key(args)
end
logger = Logger.new("#{Rails.root}/log/cache_read.log")
logger.error("cache read scope == #{cache_key.to_s}")
end
so cache_read.log file having only this method log only.