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aduncan's avatar
aduncan
New Contributor
12 years ago

[LoadUIWeb] Why does a continuous load test make the same request at slightly different times?


I have a load test with 200 virtual users. The load is continuous. All other settings are set to default. Once the test completes, I verify the Messages panel and sort it by Request #. Each Request # (1-62) displays 200 users (1-200).

Looking at the Time column, almost all users logged Request #1 at the same time 15:07:18.

However, users 128, 129, 130 logged Request #1 at 15:07:19.

Users 194, 195 logged Request #1 at 15:07:21.



If I specify a continuous load, why do 195 users make Request#1 at the same time and the remaining 5 users make the same request a few seconds later? 

Using a smaller set of virtual users, let's say 20, I do not see the discrepancy, everybody makes the same request at the same time.





Thanks for your help,

Antje  


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  • MPunsky's avatar
    MPunsky
    SmartBear Alumni (Retired)
    12 years ago
    Hello Antje,



    This is due to the number of VU's.   Even though all virtual users were set to start at the exact same time, a few vu's started slightly later due to your machine's processing overhead.   In any test with more than a very few Virtual users, it is recommended to use a load profile that staggers the start time so as to not create artificial bottlenecks.



    In addition to selecting continuous load, also select "stepwise" under load profile, and start the vu's 1 or two seconds apart.



    Hope this helps!