Re: Accessing StandardJMeterEngine.allThreads

JMeter threads simulate not users, but browsers. And when application under 
test needs to have some parallel and synchronized activity, we need some 
inter-thread interaction.

Frequent example is AJAX, where requests goes in parallel, but need some 
synchronization. For example, while file upload goes in one thread, another 
must simulate progress bar updates.

Furthermore, JMeter is very powerful and may be used to test non-Web 
systems, I myself tested MS RPC server with binary protocol, and had no 
solution for correct parallel keep-alive requests.

Of course, I understand that synchronysing = locking. I hope that just 
requesting for JMeterVariable from another thread will be not so painful 
action. And users, of course, will be warned about locks.

Giving access to allThreads opens thread manipulation for plugins, there may 
be more interesting ideas how to use this. Alas, I had to make tricks without 
it in Throughput Shaper... 

On Saturday 13 August 2011 16:36:43 sebb wrote:
> On 13 August 2011 13:13, Andrey Pohilko <[email protected]> wrote:
> > Hi all!
> > 
> > JMeter users frequently ask for some inter-thread communications on
> > JMeter forums.
> 
> JMeter threads represent independent users; it should not be necessary
> to pass data between them.
> 
> JMeter 2.5 will support setUp threads, which solve many of the use
> cases I have seen.
> 
> > I have an idea of custom function that would give information from any
> > thread for another thread. I think this will give wanted interaction.
> 
> I'd like to see some use cases that truly require cross-thread
> communication before considering this.
> The danger is that the interaction between the threads will cause
> unnecessary locking.
> 
> > The problem implementing it is that only place where all JMeterThreads
> > stored is StandardJMeterEngine.allThreads and I found no way to access
> > that list.
> > 
> > Field declaration from StandardJMeterEngine:
> >        /** JMeterThread => its JVM thread */
> >        private final Map<JMeterThread, Thread> allThreads;
> > 
> >  So my questions are:
> > 1. Is it possible to get access to that map in some read-only way (not to
> > break anything...)?
> > 2. If yes, how better do it: simple getter, or something more required?
> > I'm ready to create and submit a patch to Bugzilla.
> > 3. If the way is simple enough, could it be the part of JMeter 2.5
> > release, because waiting another year for the next release is obviously
> > undesirable?
> > 
> > Sorry, if I'm asking for too much, but with my efforts, too, JMeter
> > becoming more and more popular load testing tool.
> > 
> > Thank you!
> > --
> > Andrey Pohilko
> > JP@GC Maintainer
> > 
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