Proper way to handle error

[pkropachev]

trafficstars

Hi!

I'm trying to handle error proxy.on('error', ...), but for some reason writeHead() method is not available for response.

Could you please advice what proper way to handle error, e.g. in case target is not available?

import { program, InvalidArgumentError } from 'commander';
import httpProxy from 'http-proxy';
import express from 'express';

function checkPort(value: string) {
  const parsedValue = +value;
  if (isNaN(parsedValue)) {
    throw new InvalidArgumentError('Invalid int value.');
  }
  return parsedValue;
}

program
  .option('-b ,--bind <address>', 'bind to this address (default: all interfaces)')
  .option('-v ,--verbose', 'be verbose')
  .argument('[port]', 'bind to this port', checkPort, 8000)
  .allowExcessArguments(false)
  .parse(process.argv);

const opts = program.opts();
const [port] = program.processedArgs;

const proxy = httpProxy.createProxyServer({});

proxy.on('proxyReq', (proxyReq, req) => {
  console.log(`==> Request: ${req.socket.remoteAddress} - - "${req.method} ${req.url} HTTP/${req.httpVersion}"`);
  if (opts.verbose) {
    console.log('Headers:\n', JSON.stringify(req.headers, null, 2));
  }

  proxyReq.setHeader('User-Agent', 'http-proxy/1.0.0'); // Override User-Agent

  console.log(`<== Request: ${proxyReq.host} - - "${proxyReq.method} ${proxyReq.path}"`);
  if (opts.verbose) {
    console.log('Headers:\n', JSON.stringify(proxyReq.getHeaders(), null, 2));
    console.log(proxyReq);
  }
});

proxy.on('proxyRes', (proxyRes) => {
  console.log(
    `==> Response: ${proxyRes.socket.remoteAddress} - - code ${proxyRes.statusCode}, message ${proxyRes.statusMessage}`,
  );
  if (opts.verbose) {
    console.log('Headers:\n', JSON.stringify(proxyRes.headers, null, 2));
  }
});

proxy.on('error', (err, res) => {
  console.log('Error:', err.message);
  // Handle error here, send response to requester
});

const app = express();

app
  .get('*', (req, res) => {
    const origin_url = new URL(req.url).host;
    proxy.web(req, res, { target: `${req.protocol}://${origin_url}` });
  })
  .listen(port, opts.bind);

const host = opts.bind ? opts.bind : '::';
console.log(`Serving HTTP proxy on ${host} port ${port} ...`);

Thanks!