External API response is cut off when proxying with rewrites

[yamashhh]

Verify canary release

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

Provide environment information

Operating System:
      Platform: linux
      Arch: x64
      Version: #1 SMP PREEMPT_DYNAMIC Sun Aug  6 20:05:33 UTC 2023
    Binaries:
      Node: 16.17.0
      npm: 8.15.0
      Yarn: 1.22.19
      pnpm: 7.1.0
    Relevant Packages:
      next: 13.4.13-canary.13
      eslint-config-next: N/A
      react: 18.2.0
      react-dom: 18.2.0
      typescript: 5.1.3
    Next.js Config:
      output: N/A

Which area(s) of Next.js are affected? (leave empty if unsure)

No response

Link to the code that reproduces this issue or a replay of the bug

https://codesandbox.io/p/sandbox/competent-tess-gdqf3w

To Reproduce

1. Create a proxy for an external API endpoint by setting rewrites in next.config.js
2. Consume the API in an arbitrary component
3. Check the response from the API

Describe the Bug

The response JSON is cut off.

Expected Behavior

The entire API response is available.

Confirmed working when downgraded to v13.2.4.
repro: https://codesandbox.io/p/sandbox/vibrant-http-j6wnzr

    Operating System:
      Platform: linux
      Arch: x64
      Version: #1 SMP PREEMPT_DYNAMIC Sun Aug  6 20:05:33 UTC 2023
    Binaries:
      Node: 16.17.0
      npm: 8.15.0
      Yarn: 1.22.19
      pnpm: 7.1.0
    Relevant packages:
      next: 13.2.4
      eslint-config-next: N/A
      react: 18.2.0
      react-dom: 18.2.0

These issues/discussions might be related:

• Upgrading to NextJS 13.3.0 causes bug where POST requests are not possible to the backend API via proxy #48265
• [NEXT-835] Next.js attempts to fetch API route proxy as regular page #37783

Which browser are you using? (if relevant)

No response

How are you deploying your application? (if relevant)

No response

[icyJoseph]

Do you have to downgrade all the way to 13.2.4 for it to break? I can try to do a bit of searching on which commit broke it, but I'd just like some confirmation that 13.2.5 for example is already broken.

[yamashhh]

@icyJoseph

Hi, I've found out that this specific problem might be fixed in the latest canary version,
here is the breakdown:

Next.js version	Reproduces
v13.4.12	NO
v13.4.13	YES
v13.4.14-canary.1	NO

Confirmed on local machine:

    Operating System:
      Platform: darwin
      Arch: x64
      Version: Darwin Kernel Version 22.5.0: Thu Jun  8 22:22:22 PDT 2023; root:xnu-8796.121.3~7/RELEASE_X86_64
    Binaries:
      Node: 18.16.1
      npm: 9.5.1
      Yarn: 1.22.19
      ppm: 8.6.9
    Relevant Packages:
      next: 13.4.14-canary.1
      eslint-config-next: N/A
      react: 18.2.0
      react-dom: 18.2.0
      typescript: 5.1.3
    Next.js Config:
      output: N/A

This is the code I used, sorry I had to move from Codesandbox because it was laggy.

[icyJoseph]

Awesome, no worries. You can also use Stackblitz from GitHub, like this:

https://stackblitz.com/github/yamashhh/nextjs-issues-53737

Though there seems to be an issue with Next.js there.

Anyway, so if its fixed in canary, then I guess we could close the issue?

[yamashhh]

You can also use Stackblitz from GitHub

This is nice to know!

Thanks for checking in, I'll close this issue and see if it'll be fixed in the next stable release.

[ian-hutchinson]

@yamashhh Did you ever verify this in a stable release?

I'm seeing very similar issues in dev when proxying requests on version 13.4.19.

It feels like something has fundamentally changed with the chunking. I do not see the issue in 13.4.12.

[yamashhh]

@ian-hutchinson

Sorry, I haven't updated this thread.
It seems the problem doesn't reproduce on v13.4.19 for my specific use case.

example on stackblitz

[tkmcmaster]

My use case seems intermittent. I thought it was fixed by the canary release (and it worked locally) but is truncated still when deployed in AWS with any of the released versions 13.4.4 - 13.4.19. So I'm still rolled back to 13.3.4

[ra-lfaro]

@yamashhh Did you ever verify this in a stable release?

I'm seeing very similar issues in dev when proxying requests on version 13.4.19.

It feels like something has fundamentally changed with the chunking. I do not see the issue in 13.4.12.

exact same here

[ra-lfaro]

after lots of digging i was able to resolve my issue by removing the content-length on the proxy response. This wasnt an issue until upgrading from 13.4.12 to 13.4.19

[github-actions]

This closed issue has been automatically locked because it had no new activity for 2 weeks. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.