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From James Sutherland <ja...@cam.ac.uk>
Subject Re: FW:[mod perl + proxy returns Document has no data]
Date Fri, 05 May 2000 16:14:05 GMT
On Fri, 5 May 2000 shane@isupportlive.com wrote:
> ----- Forwarded message from lists <lists@cjx.com> -----
> I am having a tricky problem with a mod_perl backend and a vanilla proxying 
> front end
> 
> I have set up:
> 
> Apache 1.3.9 + Mod_perl 1.23 + Embperl 1.2.1 as a back-end server
> 
> Apache 1.3.9 + mod_proxy as a front-end server.
> 
> Occasionally the back-end server gets into a state where it returns
> empty documents to the front-end, and the front-end then returns a
> 
> "502 Proxy Error - document has no data" error to the client.
> 
> The only thing logged by the backend is a 200 result code with "-" for the
> amount of data transferred.
> 
> I am at a complete loss as to what is happening - server load is not
> excessive, and there are plenty of spare servers. The only thing I
> have noticed is this happens semi-consistently after a *large* file
> upload (from the client) through the proxy to the back-end server. The
> upload is handled by EmbPerl.
> 
> Once the server is in this state, it will continue serving no-data
> pages at apparently random intervals until it is restarted.
> 
> Any ideas/pointers would be much appreciated - I am stuck because the
> back-end is not giving any error messages - just a 200 code...

Apparently random intervals... hrm. Have you been able to replicate this
result connecting directly to the backend, bypassing the proxy?

My first reaction from the "random intervals" bit would be that one of the
child servers is getting broken at some point. I'd try dropping the number
of requests per child process right down, and see if that makes a
difference.


James.


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