code: public static void clearSession(final String sessionId) {
  
  		if (StringUtils.isBlank(sessionId)) {
  			return;
  		}
  
  		final App app                            = StructrApp.getInstance();
  		final PropertyKey<String[]> sessionIdKey = StructrApp.key(Principal.class, "sessionIds");
  		final Query<Principal> query             = app.nodeQuery(Principal.class).and(sessionIdKey, new String[]{sessionId}).disableSorting();
  
  		try {
  			for (final Principal p : query.getAsList()) {
  
  				p.removeSessionId(sessionId);
  			}
  
  		} catch (Exception fex) {
  
  			logger.warn("Error while removing sessionId " + sessionId + " from all principals", fex);
  		}
  
  	}
docs: Make sure the given sessionId is not set for any user.
  
  @param sessionId