Apache Response Time in Access Log How is it measured

drlchen
drlchen used Ask the Experts™
on
How is "Response Time" in the apache access log measured?
Is it measured by from the time the request was received and sent to the client?
or is it measured from the time the server received the request sent the data back to the client and then receive an ACK from the tcp handshake?

Comment
Watch Question

Do more with

Expert Office
EXPERT OFFICE® is a registered trademark of EXPERTS EXCHANGE®
Distinguished Expert 2017
Commented:
Not sure, but look at the response time in relation to the type of data being accessed as well as the quantity of data being sent.
i.e. accessing a plain 1k html file
versus a php file that also sends out 1k of data.
etc.

Did a quick search, but did not see an explanation that can be included here at this time.
See if http://mail-archives.apache.org/mod_mbox/jakarta-jmeter-user/200305.mbox/%3C3EBA37C7.26906.D9B79A7@localhost%3E.

Author

Commented:
I also found this definition on the web:

http://stein.cshl.org/~lstein/torture/torture.html 
It is the total time to send the request to the server and receive the complete response back. Lower response times are better.

This tells me it also measures the network time but the I found another article suggesting Response Time is the processing time.

Header set X-Request-Processing-Time: %D

http://prefetch.net/blog/index.php/2007/01/02/measuring-apache-request-processing-time/


Distinguished Expert 2017
Commented:
Create an html file. See what the response for it is.
Then create a PHP file that outputs the same amount of data when accessed.
See whether the response time is equivalent.
Presumably a larger data file returned would provide with more information on whether the response time if from the end of the request to the begining of the response or to the end of the response.

Author

Commented:
ok after some testing it looks like it includes network time. also

The %T and %D directives refer to the time it takes to handle the entire transaction, including the amount of time it takes for the client to transmit data. If you see wide variances in the amount of time it takes to serve the same file, it may be related to a web client network problem.

Also onlamp.com confirms this
http://onlamp.com/pub/a/apache/2004/04/22/blackbox_logs.html?page=4

Do more with

Expert Office
Submit tech questions to Ask the Experts™ at any time to receive solutions, advice, and new ideas from leading industry professionals.

Start 7-Day Free Trial