code: public void respawn(int index) {
          configurationRwLock.writeLock().lock();
          try {
              if (index >= 0 && index < servers.length) {
                  servers[index].startup();
              }
              rebalance();
          } finally {
              Info.incrementConfigRevision();
              configurationRwLock.writeLock().unlock();
          }
      }
docs: Re-Add a previously failed-over node
  @param index The index to restore. This should be an index into the
  {@link #servers} array.