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From Rainer Jung <>
Subject Re: [users@httpd] concurrent connections and netstat
Date Sat, 11 Feb 2012 12:25:33 GMT
On 11.02.2012 06:11, Ishita Kapadiya wrote:
> Hi All,
> Recently I did 'ab' test just to check performance of my new setup. so
> far, if we want to check concurrent users for that server, we were
> using "netstat -an | grep 'EST' | wc -l" to check how many total no of
> connections being used. I know we can use mod_status to get the
> accurate results. but I am curious to know, how to determine total no
> of concurrent connections being served by Apache web server at any
> point of time. Even though I have set 50 concurrent users test with
> 'ab', I hardly see 50 ESTABLISHED connections! Even I checked total no
> of CLOSE_WAIT, TIME_WAIT&   ESTABLISHED connections but that was also
> not matching with the result of what mod_status was showing.
> Can anyone let me know what could be the reason? I want to know how to
> determine that MaxClients limit is approaching just by looking into
> netstat o/p (or any other command)  without using mod_status.

netstat established and mod_status should show figures close to each 
other. The deltas are:

- If using ab without "-k" you are not using HTTP Keep-Alive, i.e. each 
request needs to open an new TCP connection. When using "-k", mod_status 
shows established connections which did not yet receive any follow-on 
requests with a "K"

- When doing HTTPS, SSL handshakes are between connection establishment 
and requests

- ab itself is single threaded but very efficient. So if you push 
concurrency very far, ab itself will need to process the results send 
back from the web server. Concurrency 50 should be fine though.

Can cou give us some numbers? If you let run ab with "-k" for a longer 
time, what numbers do you see in netstat, and which number of each 
letter typically in the server-status? Are you using HTTPS?



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