Access log timing details

[Alex Quezada <aq...@textwise.com>]

Hello,

I'm trying to debug some performance issues, and see discrepancies from
the time reported by HttpClient and Tomcat's access log.  This is for
post requests (I'm running Tomcat 6.0.18 just in case).

Does the time reported in the access log include the entire session,
including the time it took to upload the post request, or is it only the
response time once the request and payload are fully received?

I've looked around but no luck finding details on the response times.

Thanks for any info!

Alex Quezada



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Re: Access log timing details

[Tim Funk <fu...@apache.org>]

Its the time the Valve starts processing until the valve has finished 
processing.

Vague heh?

So this means that Tomcat will need to do the following first before 
timing starts
- Accept the connection
- Receive the 1st line of the request, and probably the headers such as Host
- From there - Tomcat now knows where to send the request and can 
create/invoke the Valve chain and the AccessLogValve can start its timing
- Then AccessLogValve records as its end time when the valve is finished 
its processing (which is after your servlet/jsp is already done since it 
wraps it). So (if I am correct) it may be possible that the OS could be 
buffering some bytes waiting to go out which could also cause a time 
difference.


-Tim

On 11/1/2010 12:48 PM, Alex Quezada wrote:
> Hello,
>
> I'm trying to debug some performance issues, and see discrepancies from
> the time reported by HttpClient and Tomcat's access log.  This is for
> post requests (I'm running Tomcat 6.0.18 just in case).
>
> Does the time reported in the access log include the entire session,
> including the time it took to upload the post request, or is it only the
> response time once the request and payload are fully received?
>
> I've looked around but no luck finding details on the response times.
>
> Thanks for any info!
>


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Re: Access log timing details

[Christopher Schultz <ch...@christopherschultz.net>]

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Alex,

On 11/1/2010 12:48 PM, Alex Quezada wrote:
> I'm trying to debug some performance issues, and see discrepancies from
> the time reported by HttpClient and Tomcat's access log.  This is for
> post requests (I'm running Tomcat 6.0.18 just in case).
> 
> Does the time reported in the access log include the entire session,
> including the time it took to upload the post request, or is it only the
> response time once the request and payload are fully received?
> 
> I've looked around but no luck finding details on the response times.

A bit more info might be helpful, including:

1. The size of POST request you are making
2. The physical network layout (localhost connection versus
intercontinental)
3. Some numbers you are trying to reconcile

As Tim points out, the TCP negotiation and part of the HTTP conversation
will occur 100% before the AccessValve timing starts, so HttpClient's
total-time-to-send will likely include that overhead.

Give us some time discrepancies and maybe we can comment.

- -chris
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