Redirect based on backend response

[smartmic]

Is it possible to redirect a request to another backend which was returned from original backend with a specific response status code?

Eg. I have a backend which has some business logic to respond with status code 421 (Misdirect Request) to some ill-formed requests. In that case, I want pound to hand over the request to a different backend which is configured for that requests. Nginx has some functionality to redirect to a fallback location dependend on the error code and although I looked through the pound documentation, I could not find a similar functionality. Did I miss it?

[graygnuorg]

Hello. Just to make sure I get it right: by "redirecting a request" you mean internal routing to another backend, not redirecting in HTTP sense (301, 302 response code), right?

[smartmic]

Hi Sergey,Yes, you are right and sorry if my wording was imprecise. If the web server at the target backend answers with 421, pound should route the original request to another specified backend.Thanks for answering,Martin Am 16.02.2026 um 20:59 schrieb Sergey Poznyakoff ***@***.***>: Hello. Just to make sure I get it right: by "redirecting a request" you mean internal routing to another backend, not redirecting in HTTP sense (301, 302 response code), right? —Reply to this email directly, view it on GitHub, or unsubscribe.You are receiving this because you authored the thread.Message ID: ***@***.***>

[smartmic]

Hi Sergey, that sounds very good. And thank you very much for looking into it. Meanwhile I will get familiar with the Lua extensions.

[graygnuorg]

Hi Martin. The changes are already in the repo. Please, pull. You will find the detailed discussion of various request resending techniques here: https://www.gnu.org.ua/software/pound/manual/Resend.html. In particular, your case is discussed here. As always, your feedback is most welcome.

[smartmic]

Hi Sergey,
many thanks to you for implementing this so quickly and, especially, for keeping up with excellent documentation on such new features. It demonstrates your commitment to GNU standards, which, in my opinion, is a hallmark of quality that is rare these days (unfortunately). I will definitely test the new resend functionality and let you know how it goes, but please allow me some time as I am currently quite busy.

[smartmic]

Hi Sergey, I still owe you feedback about the request resending via the Lua function - it works like a charm! Setting it up was also easy thanks to your detailed documentation. A minor thing: please update the Lua function code in the docs, there is a then missing in the if branching.

[graygnuorg]

Hi Martin. Long time no talk :) Thanks a lot for the feedback!