class ActiveSupport::Cache::MemCacheStore

def clear(options = nil)

be used with care when shared cache is being used.
Clear the entire cache on all memcached servers. This method should 
def clear(options = nil)
  @data.flush_all
rescue Dalli::DalliError => e
  logger.error("DalliError (#{e}): #{e.message}") if logger
  nil
end