Состояние сбой обновления информации об изменениях json

import React, { Component } from 'react';
import CesiumGlobe from "./cesium/CesiumGlobe";

class App extends Component {
    constructor(props){
        super(props);
        this.state = {
        pin : [],
        };
    }

    componentDidMount() { 
            let fetchData = () => { 
            let url= "localhost:3001/pin" 
            fetch(url) 
                 .then(resp=>resp.json()) 
                 .then(data =>{ 
                                 this.setState((state)=>{ 
                                      return { pin:data } 
                                  }) 
                               }); 
                 } 
           fetchData() 
           this.update = setInterval(fetchData, 2000) 
          }

    render() {
        const containerStyle = {
            width: '100%',
            height: '100%',
            top: 0,
            left: 0,
            bottom: 0,
            right: 0,
            position: 'fixed',
        };

        let icons = [];

        this.state.pin.forEach(function(element) {
            icons.push(element);
        });

        return (
            <div style = {containerStyle}>
                <CesiumGlobe icons = {icons} />

                <div style = {{position : "fixed", top : 0}}>
                    <div style = {{color : "white", fontSize: 40, }}>
                        Text Over the Globe
                    </div>

                    <button style = {{fontSize : 40}} onClick = {this.handleFlyToClicked}>
                        Jump Camera Location
                    </button>
                </div>
            </div>
        );
    }
}

export default App;

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import './index.css';

import "cesium/Source/Widgets/widgets.css";

import buildModuleUrl from "cesium/Source/Core/buildModuleUrl";
buildModuleUrl.setBaseUrl('./cesium/');

function tick() {
ReactDOM.render(
  <App />,
  document.getElementById('root')
);
}

setInterval(tick, 1000);