code: public String getNewSessionIdIfNodeFromSessionIdUnavailable( @Nonnull final String sessionId ) {
  		if ( isEncodeNodeIdInSessionId() ) {
  	        final String nodeId = _sessionIdFormat.extractMemcachedId( sessionId );
  	        final String newNodeId = _nodeIdService.getNewNodeIdIfUnavailable( nodeId );
  	        if ( newNodeId != null ) {
  	            return _sessionIdFormat.createNewSessionId( sessionId, newNodeId);
  	        }
  		}
  		return null;
  	}
docs: Returns a new session id if node information shall be encoded in the session id
  and the encoded nodeId given one is <code>null</code> or not available.
  @param sessionId the session id that is checked.
  @return a new session id or <code>null</code>.