code: public String getNextAvailableNodeId(final String nodeId) {
  	    String result = nodeId;
  	    do {
  	        result = _primaryNodeIds.getNextNodeId(result);
  	        if(result != null && result.equals(nodeId)) {
  	            result = null;
  	        }
  	    } while(result != null && !isNodeAvailable(result));
  	    return result;
  	}
docs: Get the next available node id for the given one, based on the primary node ids
  (memcachedNodes without failoverNodes). For the last node id the first one is returned.
  If this list contains only a single node, conceptionally there's no next node
  so that <code>null</code> is returned.
  @return the next available node id or <code>null</code> if there's no next available node id.
  @see #getNextPrimaryNodeId(String)
  @see #isNodeAvailable(String)