def get_title(self, url):
   key   = self.create_title_key(url)
   value = memcache.get(key)
   if value is None:
     # MEMO: 1度だけ再試行する
     try:
       value = HatenaBookmark.get_title(url, self.username, self.password)
     except urlfetch.DownloadError:
       logging.info("retry download")
       value = HatenaBookmark.get_title(url, self.username, self.password)
     memcache.add(key, value, self.ttl)
   return value