code: @RequirePOST
      public void doConfigSubmit( StaplerRequest req, StaplerResponse rsp ) throws IOException, ServletException, FormException {
          checkPermission(CONFIGURE);
  
          String proposedName = Util.fixEmptyAndTrim(req.getSubmittedForm().getString("name"));
          Jenkins.checkGoodName(proposedName);
  
          Node node = getNode();
          if (node == null) {
              throw new ServletException("No such node " + nodeName);
          }
  
          if ((!proposedName.equals(nodeName))
                  && Jenkins.getActiveInstance().getNode(proposedName) != null) {
              throw new FormException(Messages.ComputerSet_SlaveAlreadyExists(proposedName), "name");
          }
  
          String nExecutors = req.getSubmittedForm().getString("numExecutors");
          if (StringUtils.isBlank(nExecutors) || Integer.parseInt(nExecutors)<=0) {
              throw new FormException(Messages.Slave_InvalidConfig_Executors(nodeName), "numExecutors");
          }
  
          Node result = node.reconfigure(req, req.getSubmittedForm());
          Jenkins.getInstance().getNodesObject().replaceNode(this.getNode(), result);
  
          // take the user back to the agent top page.
          rsp.sendRedirect2("../" + result.getNodeName() + '/');
      }
docs: Accepts the update to the node configuration.