Cloudflare is returning an error 520 when my web server issues HTTP 302

[arbel.gros]

What is the name of the domain?

arbel.gr

What is the error number?

520

What is the error message?

Web server is returning an unknown error

What is the issue you’re encountering

Cloudflare is returning an error 520 when my web server issues a redirect (HTTP 302)

What are the steps to reproduce the issue?

To reproduce: access https://arbel.gr/redirectme.

Or curl it:
[curl -v arbel.gr/redirectme* Host arbel.gr:80 was resolved.* IPv6: (none)* - Pastebin.com]

Compare this with accessing the raw IP, bypassing Cloudflare:

[curl -v 15.156.205.117/redirectme* Trying 15.156.205.117:80...* Connected - Pastebin.com]

It’s not clear to me why Cloudflare calls this an “unknown error”. All I’m trying to do is send 302 Found.

[fritex]

@arbel.gros

arbel.gr

@arbel.gros

520

I cannot reproduce the same error anymore.
Your Website is working fine from me end, using Cloudflare nameservers and DNS records proxied .
Could you confirm?

Furhtermore, may I ask which steps for troubleshooting 520 error have you tried already?

Community Tip - Fixing Error 520: Web server is returning an unknown error

Error Try the suggestions in this Community Tip to help you fix “Error 520: Web server is returning an unknown error”. Background Error 520 is essentially a catch-all response when something unexpected happens or when the origin server incorrectly interprets or does not tolerate a request due to a protocol violation or an empty response. A 520 error occurs when the connection started on the origin web server, but that the request was not completed. The most common reason why this would occur …

Troubleshooting Cloudflare 5XX errors | Cloudflare Support docs

[arbel.gros]

@fritex Thanks for the reply! To troubleshoot I tried tweaking the HTTP status code and I found that HTTP 303 returned the same error. Unfortunately Cloudflare is very vague and isn’t explaining exactly what’s wrong (e.g. “invalid HTTP format”). Maybe I will experiment some more. But you said you’re able to access https://arbel.gr/redirectme - could you share what output you get when you curl the page?

curl -v arbel.gr/redirectme

Here’s what I’m seeing:

[arbel.gros]

I figured it out!

I need to have the string \r\n\r\n (two newlines) after the response. It wasn’t working because I only had one newline. I’m not sure why Cloudflare has this requirement but I hope this helps someone!