Re: Connection filters and Keep-Alive

[Stas Bekman <st...@stason.org>]

Stas Bekman wrote:
> Stas Bekman wrote:
> 
>> Mathias Herberts wrote:
>>
>>> Hi,
>>>
>>> still in the process of building an Input Connection Filter I noticed 
>>> something wrong with all Connection Filter examples I could find 
>>> (including HTTPHeadersFixup), in case the connection is instructed to 
>>> be kept open with 'Connection: Keep-Alive', several requests will be 
>>> run through the same instance of the filter, therefore it is not 
>>> possible to safely ignore the possible body of a POST (or DAV) 
>>> request. One must keep track of Content-Length and only ignore body 
>>> if 'Connection: close'  was issued (as per RFC 2616).
>>>
>>> Anybody else aware of that?
>>
>>
>>
>> Not me. I'm still learning the topic ;) Thanks for the heads up, 
>> Mathias. I have never tried with 'Connection: Keep-Alive', though I 
>> think there must be a better way to tell separate requests from each 
>> other. I'll investigate this and get followup on this.
> 
> 
> The net thrown in the httpd-dev sea came back empty. The fish is hiding 
> behind the rocks, scratching their private itches.
> 
> It seems that Apache provides no way to tell one request over another 
> when Keep-Alive is in effect. I need to look at the ap_discard_body 
> function, since somehow it knows when there is no more body to read.
> 
> Meanwhile I have the following filter tandem idea that may do the trick. 
> We could add a connection response filter, whose only purpose will be to 
> set a note in the connection object when it sees the response headers (I 
> don't think EOS is sent in the response stream) flagging the incoming 
> filter mate that the next time it's invoked it'll be a new request. That 
> will only work if after sending the headers, it's  known that the 
> request body is fully consumed. I think that's the case, but I'm not 
> 100% sure.

I first successfully implemented the tandem trick to learn that when the 
method is HEAD, the filter won't see the EOS bucket.

Digging into the Apache source I've found a much simpler way to handle the 
context reset, using $c->keepalives counter, which I've exposed recently (i.e. 
you need the current cvs or wait till 1.99_13 is released).

That technique is documented at:
http://perl.apache.org/docs/2.0/user/handlers/filters.html#Connection_Filters_over_KeepAlive_Connections

I've just uploaded a new version of 
Apache-Filter-HTTPHeadersFixup-0.02_01.tar.gz on CPAN, which now uses that 
technique to handle keepalive connections.

__________________________________________________________________
Stas Bekman            JAm_pH ------> Just Another mod_perl Hacker
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