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Monday, December 8, 2008

How to avoid think time / wait time from being accumulated in Custom Timers.

In Silk Performer custom Timers are used to generate response time around
transactions. It is usually inserted in the script generated by SP recorder. In
a typical script it looks as following -

==========================================================
MeasureStart("1020_ RANK_PREFERENCE"); // Custom Timer - Start for Rank
Prefpage

WebUrl("https://test-qa.test.edu/testtesting/images/arrow.png");
**** Few more functions***
**************************
**** Few more functions***

MeasureStop("1020_ RANK_PREFERENCE"); // Custom Timer - stop for
Rank Pref page
==========================================================

With the inclusion of Think Timer (wait time kept deliberately to simulate
real user behaviour as a typical user waits on a page before performing
any action) script would look as following -

===========================================================
MeasureStart("1020_ RANK_PREFERENCE"); // Custom Timer - Start for Rank
Pref page

WebUrl("https://test-qa.test.edu/testtesting/images/arrow.png");

ThinkTime(154.56); // Think timer inserted in middle of Measure Start and
Stop timers.

**** Few more functions***
**************************
**** Few more functions***

MeasureStop("1020_ RANK_PREFERENCE"); // Custom Timer - stop for Rank
Pref page
============================================================

Having think time in middle of Start and Stop timers would cause think time to
be added to the overall response time which eventually would give a false
impression about the response time of page.
To avoid think time from being added to custom timer one needs to stop timing
measurement before Think Time and must resume it after it. This is as following
-

==============================================================
MeasureStart("1020_ RANK_PREFERENCE"); // Custom Timer - Start for Rank Pref
page

WebUrl("https://test-qa.test.edu/testtesting/images/arrow.png");

MeasurePause("1020_ RANK_PREFERENCE"); // Pause the time measurement
ThinkTime(154.56); // Think Time
MeasureResume("1020_ RANK_PREFERENCE"); // Resume the time measurement

**** Few more functions***
**************************
**** Few more functions***

MeasureStop("1020_ RANK_PREFERENCE"); // Custom Timer - stop for Rank
Pref page
=============================================================

This how think time can be stooped from getting added to custom timers.

fwait-Parameter:
When browser-level Web traffic is recorded using the Recorder, a wait time is
included at the end of recorded functions to tell the replay engine how long to
wait before executing the next function in the script. In WebURL function it
look as -

==============================================================
WebUrl("http://www.shopit.com/ad.gif", 17.2); // Here 17.2 is fwait parameter.
==============================================================
The wait time times simulate:

* The time the browser needs to parse out links of embedded documents (e.g.
images, etc).
* A users thinking time.

This wait time is ignored in Stress Test mode.

But again this wait gets added to custom timers and results in overall high
response time. If WebUrl function is just a call to image then it can be
manually removed from the script, But if its need is indispensable then it can
be replaced with equivalent Think Timer as -

===========================================================
WebUrl("http://www.shopit.com/ad.gif"); // WebURL function with out fwait.
ThinkTime(17.2); // Think time to simulate the wait period
===========================================================

Here again time measurement should be stopped before Think Time and should be
resumed just after it as illustrated above.
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