Re: HAproxy returns HTTP 502 error when backend returns an HTTP 302 with a long Location:

On 19 July 2011 21:55, Willy Tarreau <w#1wt.eu> wrote:
> On Tue, Jul 19, 2011 at 11:06:58AM -0700, carlo wrote:
>> Check out tune.bufsize and tune.maxrewrite in the Performance Tuning section
>> of the HAProxy docs.
>
> Indeed. I would add something : an application which generates headers or
> URLs that are *that* long will never reliably work over the internet and
> will experience trouble through a number of components. For instance,
> Apache limits each line to 8192 bytes, very close to your header's length,
> and Apache is present everywhere.
>
> Also, the client will have to repost this request, making it even longer.
> BTW, if the page you're pointing to contains images, all of them will be
> fetched with a Referer containing that long URL. This is a very bad idea
> again. Imagine if the page contains 50 objects (css, js, images, ...),
> then the browser has to upload 51 times 8 kB or half a megabyte. This can
> take a huge time in many environments (ADSL, 3G, ...). All this really
> translates a bad initial design which should be fixed one way or another.
>
> Last, I invite you to read suggestions from the HTTP spec here :
>
>   http://tools.ietf.org/html/draft-ietf-httpbis-p1-messaging-15#section-3.2
>
>  "Various ad-hoc limitations on header length are found in practice.
>   It is RECOMMENDED that all HTTP senders and recipients support
>   messages whose combined header fields have 4000 or more octets."
>
> You're more than twice the recommended size, you're asking for trouble.
>
> In haproxy, to workaround the default limit, you can increase
> tune.bufsize and decrease tune.maxrewrite. I'm used to set them to
> 8kB and 1kB respectively because that's fine everywhere. You can
> set maxrewrite to 1kB and bufsize to 16kB to see if that fixes your
> issue, but I really invite you to fix the application before it's
> too late !
>
> Regards,
> Willy

Thanks Carlo & Willy. I am in agreement, this does seem like a very bad idea, I'll have to see if they can make a design change to prevent this from becoming a future headache.

Graeme. Received on 2011/07/19 22:37