How to count dropped connections

[Shachar Shemesh]

Amos Shapira wrote:
> 2009/6/9 shimi <linux-il at shimi.net>:
>   
>> At what layer do you define "dropping a request" ? Not accepting a TCP
>> connection (4) ? Failure to  complete the request from the reverse proxy to
>> the backend servers (HTTP error) (assuming you have backend servers - the
>> network structure is not obvious from your original message)?
>>     
>
> We use Linux Virtual Server (LVS) in DR mode (i.e. packets come in to
> a virtual IP through the LVS, outgoing replies are sent directly from
> the Real Servers) in load-balancing (i.e. multiple servers accept and
> handle requests in parallel).
>
> Some of the Real Servers are configured as "persistent", i.e. all
> requests from same client within a two-minute period will be handled
> by the same Real Server, due to functional requirements, others don't
> have this requirement.
>
>   
>> What answers the TCP requests to port 80?
>>     
>
> All requests are handled by Apache 2.2 modules written in C++.
>
>   
>> Do you use efficient HTTP handlers already, e.g. Lighttpd or even better,
>> nginx? :)
>>     
>
> We looked at it (lighttpd) and back then didn't see a justification to
> make the switch (already had in-house knowledge to write Apache
> modules vs. another learning period to take with lighttpd, plus
> Apache's flexibility back when we didn't know what we'll need was a
> factor, e.g. we also had php, perl and CGI code running around at the
> beginning).
>
> As far as we can tell the bulk of the load is inside our own
> home-grown module, not inside Apache.
>
> What I'd like to know is how many failed connections clients receive,
> be it "connection refused" or time outs.
>
>   
If it's at the TCP level you want to know this, a sniffer is probably 
your best approach. I'm not aware of any ready made one, but writing a 
dedicated one (even without libpcap) that is capable of living up to the 
load you describe should not be too big a project.

Contact me if you want a quote :-)

Shachar

-- 
Shachar Shemesh
Lingnu Open Source Consulting Ltd.
http://www.lingnu.com

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