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From "Robin D. Wilson" <>
Subject How would you go about creating a new Thread Group type?
Date Mon, 17 Oct 2016 21:08:40 GMT
Just throwing this out there - to see if anyone wants to lead a code-level newbie down the
right path. I've been using JMeter for
8-9 years now, and really like it. But one thing that bugs me is the way the Thread Group
works. Specifically, the idea of the
"loops" bothers me.


Consider this scenario:


1)     100 "users" (e.g., threads)

2)     10 loops 

3)     Test has 10 HTTP Requests in it


By this logic, you should end up with 100 (users) X 10 loops X 10 HTTP Requests = 10,000 requests.


And you do.


BUT, what you actually get when you run the test isn't as clear as you think. It is basically
100 threads, each running 10 times,
and each thread loop running 10 HTTP requests in sequence.


Here's the problem, if thread 1 completes its 10 loops in 100 seconds, but threads 2-100 take
200 seconds to complete their 10
loops. The load will be reduced to only 99 simultaneous threads (users) for the last 100 seconds
of the test run. That's not a
'huge' deal, but it can affect the perception of the test if you look at it more like threads
1-50 finish in 100 seconds, and
threads 51-100 take an extra 100 seconds after that to complete. Then only half of your test
cycle was at the required 'max' load
you wanted to create, while the other half was at 50% of the required load. (It is reasonably
possible that I'm just misinterpreting
how it actually works, but it appears to work like this from my experience since I can see
threads continuing to process after some
threads appear to stop - and it lasts longer than it takes to get through the entire cycle
- sometimes for several minutes at the
end of a test run.)


I'd like to create a new Thread Group that doesn't assign the thread to the loop until it
starts again at the top of the cycle. So
if thread-1 finishes really fast, and there are still loops to run - it just picks up another
loop and runs it. I would always want
to maintain at least 100 threads executing, so long as there were loops left to run. So basically,
you multiply the number of loops
by the number of threads (1000 in my example), and your 100 threads always restart until there
are no loops left to run. Then the
longest period you have where you aren't fully loading the servers is just the last loop for
every thread. 


BUT, I am not 100% sure where I would start in the source code. I have programmed before (a
long time ago), but if someone could
point me in the right direction (like, which source files would need to be modified, and how
would I register my new Thread Group as
a different option), I think I could figure it out pretty quickly.



Robin D. Wilson



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