On Jun 23, 2011, at 1:01 PM, sebb wrote: > On 23 June 2011 11:06, Kirk <[email protected]> wrote: >> One has to really be careful with JMeter's threading model. It has the >> potential to act as the bottleneck in your load test. I've seen a few teams >> chasing all kinds of things in the app server when they really needed to be >> looking at what was coming behind them. IMHO, a thread per user is an easy >> model to grasp but is much easier to set yourself up for failure. Case in >> point, and earlier suggestion that if the response times are greater than >> the desired rate of arrival at the server, the throughput will drop 'cos >> JMeter will simply not have enough threads to trigger the request. Hence, >> the bottleneck in the system will be JMeter. While some might argue that >> this is sill ok (and in a number of cases it's not harmful), an event based >> model would be much more scalable and less prone to this type of testing >> failure.. artificial throttling of throughput. > > If I understand you correctly, what you are saying is that the maximum > throughput for a single JMeter thread is limited by the response time > of the server, because JMeter waits for the sample to complete before > issuing the next request. > > Have I got it right?
Judging by your response I don't think that my message was clear. If I put a single usage pattern (pattern that a user executes to complete a multi-step business transaction) into a single thread group and then execute that thread group then there *is* a real possibility of JMeter/test harness thread starvation. > > If so, for plain HTTP requests, IMO the model does agree with how > users generally behave, because they won't generally click another > link until the previous request has completed. > > For pages with embedded resources, modern browsers download these in > parallel; this has been implemented and will be in the next JMeter > release. > [And it already has the Cache Manager] > > For most other protocols, the synchronous thread model is OK, as far as I > know. If you want to know why LoadRoader or slikrunner... have little issue loading to 1000s of users from a single instance, take a look at the internal differences in threading model. Look, I've no interest in getting into a pissing match with you 'cos as I mentioned before, what is here is no small feat to put together. Kind regards, Kirk --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
