docs: public void addSeenUrl(String url, int docId) throws UnsupportedEncodingException {
          String canonicalUrl = URLCanonicalizer.getCanonicalURL(url);
          if (canonicalUrl == null) {
              logger.error("Invalid Url: {} (can't cannonicalize it!)", url);
          } else {
              try {
                  docIdServer.addUrlAndDocId(canonicalUrl, docId);
              } catch (RuntimeException e) {
                  if (config.isHaltOnError()) {
                      throw e;
                  } else {
                      logger.error("Could not add seen url: {}", e.getMessage());
                  }
              }
          }
      }