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From Michal Mertl <>
Subject Re: problems with mod_proxy and mod_cache on 2.X
Date Thu, 07 Apr 2005 12:44:42 GMT
Michal Mertl wrote:
> Graham Leggett wrote:
> > Michal Mertl wrote:
> > 
> > > I'm developping caching proxy server with antivirus. The best/cleanest
> > > solution seems to me apache2 + mod_clamav. I had to fix mod_clamav
> > > substantialy but now I stumbled across some bug in mod_proxy. I know
> > > about several situations where the pages get loaded wrongly regardless
> > > of the browser and or apache2 version (2.0.53 or 2.1.4). Fortunately the
> > > situation is quite rare.
> > > 
> > > The best example is The page loads well with
> > > Apache1.3 base proxy.
> > 
> > Can you send more details on the problem that you found?
> I really don't know exactly. I thought the problem is much more
> widespread but now it seems it's quite rare.
> The problem seems to be in particular site (webserver) which responds
> from time to time to the same request differently. I've never seen error
> message in the browser when going direct of through Apache 1.3 based
> proxy. I suspect it was just luck I didn't notice it with 1.3 now. On
> the other hand I've seen it when using FreeBSD fetch utility (similar to
> wget) - it also fails the link from time to time with "unknown error"
> message.
> Failing URL is for example this one (it's random):
> It's tempting to say it's the server's fault but because it doesn't
> appear in direct connection it's unfortunate. I managed to get tcpdump
> of a failed request with fetch. It really is server's fault - instead of
> replying with the data it just closes the connection. A second later the
> same request works. It seems the browser must react to the broken server
> by retrying while mod_proxy sends to the client the Bad Gateway error
> (which seems correct).
> The bad thing is that the server in question is (I thing) pretty heavily
> used on some important pages on the Czech Internet. Unfortunately I
> don't browse much in there but the users will surely do so I can't be
> sure how often the problem appears. The server is an advertising server.
> I'll check with squid - if it sends error to the client I would say it's
> a server's problem and give up on the issue. 

FYI: The page doesn't work with squid either. It only doesn't display as
visible an error but it operates the same.

In the squid log the problem can be seen like this:

1112876066.989     48 X.X.X.X TCP_MISS/000 1 GET - DIRECT/ -

Normally squid displays HTTP return code in place of '000'.

No big problem then.



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