docs: public int getDocId(String url) {
          synchronized (mutex) {
              OperationStatus result = null;
              DatabaseEntry value = new DatabaseEntry();
              try {
                  DatabaseEntry key = new DatabaseEntry(url.getBytes());
                  result = docIDsDB.get(null, key, value, null);
  
              } catch (RuntimeException e) {
                  if (config.isHaltOnError()) {
                      throw e;
                  } else {
                      logger.error("Exception thrown while getting DocID", e);
                      return -1;
                  }
              }
  
              if ((result == OperationStatus.SUCCESS) && (value.getData().length > 0)) {
                  return Util.byteArray2Int(value.getData());
              }
  
              return -1;
          }
      }