public static function getReadMemcacheKey($url, $range) {
    $key = sprintf(self::MEMCACHE_KEY_FORMAT, $url, $range);
    if (strlen($key) > self::MEMCACHE_KEY_MAX_LENGTH) {
      $hash = hash("ripemd256", $key);
      $key = sprintf(self::MEMCACHE_KEY_HASH_FORMAT, $hash);
    }
    return $key;
  }