How to calculate sessions per hour in performance testing? -
Little's Law
Calculating Sessions per hour: For this discussion, we will be focusing
on a session as the total time for the user group to finish one complete
set of transactions. We may wish to know the number sessions that will
be completed for any given number of virtual users.
- Example
1:- If a baseline test shows that a User Type takes a total of 120
seconds for a session, then in an hour long steady state test this User
Type should be able to complete 3600 / 120 = 30 sessions per hour.
Twenty of these users will complete 20 x 30 = 600 of these session in an
hour. In other cases, we have a set number of sessions we want to
complete during the test and want to determine the number of virtual
users to start.
- Example 2:Using the same conditions in our
first example, if our target session rate for sessions per hour is 500,
then 500 / 30 = 16.7 or 17 virtual users. A formula called Little's Law
states this calculation of VirtualUsers in slightly different terms.
- Using
Little's Law with Example 2:
wV.U. = R x D where R = Transaction
Rate and D = Duration of the Session
If our target rate is 500
sessions per hour (.139 sessions/sec) and our duration is 120 seconds,
then Virtual Users = .139 x 120 = 16.7 or 17 virtual users.
No comments:
Post a Comment