Didn't get multipart/form-data value from proxy server to main server

[amitkTechno]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the issue has not already been raised

Issue

Node.js version

14.21.2

Npm version

6.14.17

Fastify version

4.24.3

Description

I am using @fastify/express 2.3.0 and @fastify/http-proxy 9.3.0 and @fastify/multipart 8.0.0. Trying to upload a file using express-fileupload 1.1.10. When making a request with a file, get the file details in proxy server, but didn't get the file details in the main server.

Configuration

const express = require('express');
const router = express.Router();
async function startOrigin() {
  const server = Fastify({
    logger: false,
  })
  server.register(require('@fastify/multipart'));
  server.register(require('@fastify/express')).after(() => {
    server.use(express.urlencoded({ extended: true })); // for Postman x-www-form-urlencoded
    server.use(express.json());
    server.use('/api', router);

  });
  router.post('/hello', async (req, res) => {
    const data = await req.file();
    console.log(data);
    res.json({ hello: 'world' });
  });
  await server.listen();
  return server;
}
async function startProxy(upstream) {
  const proxyServer = Fastify({
    logger: false,
  });
  proxyServer.register(require('@fastify/multipart'));
  proxyServer.register(proxy, {
    upstream,
    undici: true,
    preValidation: async (req, reply) => {
      const data = await req.file();
      console.log(data);
    },
    replyOptions: {
      rewriteRequestHeaders: (req, headers) => {
        return {
          ...headers,
          authorization: 'Bearer token' 
        };
      }
    }
  });
  await proxyServer.listen({ port: process.env.PORT || '3000' });
  return proxyServer;
}

async function run() {
  const origin = await startOrigin();

  const upstream = `http://localhost:${origin.server.address().port}`;

  console.log('origin started', upstream);

  const proxy = await startProxy(upstream);

  console.log('proxy started', `http://localhost:${proxy.server.address().port}`);
}

run();

am I doing wrong something. Please check this.

Thanks in advance

[mcollina]

What's happening is that the multipart body is parsed at the proxy and not forwarded through.
To fix remove the use of multipart and preValidation option.