javascript无法向Eureka服务器注册React应用程序

Question

错误：

Access to fetch at 'http://127.0.0.1:8761/eureka/apps/auth0-react-sample' from origin 'http://localhost:3000' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

代码：

索引。js（React应用程序）

    const PORT = process.env.PORT || 3000;
    const eurekaHelper = require('./eureka-helper/eureka-helper');
    
    const Eureka = require('eureka-js-client').Eureka;
    
    // const PORT = 3000;
    // const HOST = '0.0.0.0';
    
    // example configuration
    const client = new Eureka({
      // application instance information
      instance: {
        app: 'auth0-react-sample',
        hostName: 'localhost',
        ipAddr: 'localhost',
        //statusPageUrl: 'http://localhost:3000/',
        port: 3000,
        vipAddress: 'auth0-react-sample',
        dataCenterInfo: {
          name: 'default',
        },
        registerWithEureka: true,
        fetchRegistry: true,
      },
      eureka: {
        // eureka server host / port
        host: 'localhost',
        port: 8761,
        servicePath: '/eureka/apps',
      },
    });
    
    
    
    // Listen on a specific host via the HOST environment variable
    var host = process.env.HOST || '0.0.0.0';
    // Listen on a specific port via the PORT environment variable
    var port = process.env.PORT || 3000;
    
    
    const onRedirectCallback = (appState) => {
      history.push(
        appState && appState.returnTo ? appState.returnTo : window.location.pathname
      );
    };
    
    // Please see https://auth0.github.io/auth0-react/interfaces/auth0provideroptions.html
    // for a full list of the available properties on the provider
    const config = getConfig();
    
    const providerConfig = {
      domain: config.domain,
      clientId: config.clientId,
      ...(config.audience ? { audience: config.audience } : null),
      redirectUri: window.location.origin,
      onRedirectCallback,
    };
    
    
    client.start(error=>{
      console.log(error || 'NodeJS Eureka started');
      ReactDOM.render(
        <Auth0Provider {...providerConfig}>
          <App />
        </Auth0Provider>,
        document.getElementById("root")
      );
    });
    
    eurekaHelper.registerWithEureka('auth0-react-sample', PORT);
    

serviceWorker.unregister();

尤里卡助手。js

    const Eureka = require('eureka-js-client').Eureka;
const eurekaHost = (process.env.EUREKA_CLIENT_SERVICEURL_DEFAULTZONE || '127.0.0.1');
const eurekaPort = 8761;
const hostName = (process.env.HOSTNAME || 'localhost')
const ipAddr = '127.0.0.1';

exports.registerWithEureka = function(appName, PORT) {
    const client = new Eureka({
    instance: {
      app: appName,
      hostName: hostName,
      ipAddr: ipAddr,
      port: {
        '$': PORT,
        '@enabled': 'true',
      },
      vipAddress: appName,
      dataCenterInfo: {
        '@class': 'com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo',
        name: 'MyOwn',
      },
    },
    //retry 10 time for 3 minute 20 seconds.
    eureka: {
      host: eurekaHost,
      port: eurekaPort,
      servicePath: '/eureka/apps/',
      maxRetries: 10,
      requestRetryDelay: 2000,
    },
  })

client.logger.level('debug')

client.start( error => {
    console.log(error || "user service registered")
});



function exitHandler(options, exitCode) {
    if (options.cleanup) {
    }
    if (exitCode || exitCode === 0) console.log(exitCode);
    if (options.exit) {
        client.stop();
    }
}

client.on('deregistered', () => {
    process.exit();
    console.log('after deregistered');
})

client.on('started', () => {
  console.log("eureka host  " + eurekaHost);
})

process.on('SIGINT', exitHandler.bind(null, {exit:true}));
};