WEIRD: 502 Errors for ONE Visitor on Old Mobile Device On Verizon ISP

This happened last year to one person and this year to someone else

[martinibuster]

Had the weirdest thing happen on one of my sites. Just ONE person was getting a 502 Bad Gateway. This happened to ONE other person last year and I couldn't figure it out last year (but I did solve it this year).

The NGINX error log:

upstream sent too big header while reading response header

Both visitors were on older mobile devices and coincidentally (?) both were on Verizon ISP.

I checked my NGINX error logs and it was happening only to the ONE person, just like the other person last year.

It wasn't happening to anyone else.

So this time I figured out how to fix it (increasing some buffer values).

But I don't know WHY those people on their legacy devices were causing 502 errors just for them (not sitewide).

Any idea why?

[lucy24]

upstream sent too big header while reading response header

Does that mean part of a request header, something you'd be able to log and inspect at your end? Mobile devices do tend to send some awfully inexplicable headers--the kind where you look at them and think “What, exactly, am I expected to do with this information?”

[martinibuster]

Hmm... Yeah, I must have a log of that visit I can look at, LOL. I just looked at the error log. Duh!

So some old devices provide weird headers that blow up websites?

I didn't know! :o