Hostname of request object in middleware is always 'localhost'

Verify canary release

• I verified that the issue exists in Next.js canary release

Provide environment information

    Operating System:
      Platform: darwin
      Arch: x64
      Version: Darwin Kernel Version 21.5.0: Tue Apr 26 21:08:22 PDT 2022; root:xnu-8020.121.3~4/RELEASE_X86_64
    Binaries:
      Node: 14.19.1
      npm: 8.12.1
      Yarn: 1.22.18
      pnpm: N/A
    Relevant packages:
      next: 12.1.7-canary.31
      react: 18.1.0
      react-dom: 18.1.0

What browser are you using? (if relevant)

No response

How are you deploying your application? (if relevant)

No response

Describe the Bug

(I edited local /etc/hosts file to reproduce the issue, but the same issue happens even when I deploy an app and connect a domain to that.)

Whatever domain is being used, request object, which is an input of a middleware function, always has "localhost" as its hostname.

I use middleware to store all the access logs to an ES storage. Because request.url or request.nextUrl always has ‘“localhost”’ as its hostname, I cannot distinguish stage.something.com from something.com or dev.something.com.

Expected Behavior

It should has the actual URL information. (in the example above, hostname should be test.domain.ai).

To Reproduce

1. npx create-next-app@latest --typescript
2. add middleware function

   /* eslint-disable @next/next/no-server-import-in-page */
   import { NextResponse } from "next/server";
   import type { NextMiddleware } from "next/server";
   
   const middleware: NextMiddleware = (request) => {
     const response = NextResponse.next();
   
     const { url, nextUrl } = request;
     const { host, hostname } = nextUrl;
     console.log({ url, host, hostname });
   
     return response;
   };
   
   export default middleware;
   

3. edit local /etc/hosts

   127.0.0.1 test.domain.ai
   

4. access test.domain.ai from any web browser

[hannesl]

Thanks @balazsorban44 but for my use case I depend on being able to get the actual hostname that the request uses. It’s often the case that a website can be reached through more than one hostname, and for me that information is important.

My use case aside, I think most people would expect a request object to reflect the actual request URL, not a URL that is constructed from the application config.

[balazsorban44]

Understandable, but this is to increase security when hosting outside of Vercel, as you may understand. Closing with the above suggestion https://github.com/vercel/next.js/issues/37536#issuecomment-1157000990.

Again, use it with care, only if you trust your proxy.