code: public void clear() throws IOException {
      try {
        zooKeeper.setData(fullyQualifiedZNode, null, expectedZNodeVersion.get());
      } catch (KeeperException.BadVersionException e) {
        LOG.error(fullyQualifiedZNode + " has been updated by another process",
            e);
        throw new StaleVersionException(fullyQualifiedZNode +
            "has been updated by another process!");
      } catch (KeeperException e) {
        keeperException("Unrecoverable ZooKeeper error clearing " +
            fullyQualifiedZNode, e);
      } catch (InterruptedException e) {
        interruptedException("Interrupted clearing " + fullyQualifiedZNode, e);
      }
    }
docs: Clear out the data in the ZNode specified in the constructor to indicate
  that no segment is currently in progress. This does not delete the
  actual ZNode.
  @throws IOException If there is an unrecoverable error talking to
  ZooKeeper