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