nginx-1.4 proxy requests being continious

[Maxim Dounin]

Hello!

On Sat, May 11, 2013 at 04:13:38PM +1000, Daniel Black wrote:

[...]

> > A request for /img/file_doesnt_exist.jpg results in the backend server
> > (192.168.129.90) getting continuous requests for the same file (which
> > doesn't exist there either so 404 each time), while the original
> > requester waits and nginx keeps asking the backend the same.
> > 
> > I'm using the nginx-1.4.1 from the debian squeeze repository.

[...]

> > server 173.230.136.6 backup;

[...]

> > proxy_next_upstream error timeout invalid_header http_500 http_502
> > http_503 http_504 http_404;

What you describe looks very familiar - there was such a bug which 
manifested itself with backup servers and proxy_next_upstream 
http_404.  It was fixed in 1.3.0/1.2.1 though:


    *) Bugfix: nginx might loop infinitely over backends if the
       "proxy_next_upstream" directive with the "http_404" parameter was
       used and there were backup servers specified in an upstream block.

Are you sure you are using 1.4.1 on your frontend (note: it's 
usually not enough to check version of nginx binary on disk, as 
running nginx binary may be different)?  Could you please provide 
frontend's debug log?

-- 
Maxim Dounin
http://nginx.org/en/donation.html