Virtual Users in nGrinder is mapped into threads. If there are 1000 threads which runs a script, which means there are 1000 virtual users. nGrinder has a little different approache from other peformance test tools. Instead of mimicking the user real behavior, we more focus on the how to make the server reach its limit. So we don't recommend to use think time concept in the scripts.
However if you want to simulate real user behaviors and really want to run the script by the huge count of virtual users, follow the below instructions. For example... if you want to have 10000 vusers,
- Prepare the 5 good agent machines. You may need machines with 8 cores and 16G memory.
- Extends the limit of vuser count by setting agent.max.vuser to 2000
- Simulate thinking time with grinder.sleep(how_much_sleep_in_milliseconds) in the script
- When you configure the vuser count, please set the process around 20 and thread around 100.
There is always possibility to cause the memory related problem. So you need to set process and thread count very carefully.
Please refer Process And Thread for detail. If you need more vusers, please consider add more agents.
Actually in our side, we set the vuser limit as 300 with 4GB ram and 2 core CPU agent machines. It was very stable with that number. We expect 1000 vusers can be runnable if you have 8GB and 4 core CPU machines.
If you don't know how much vusers you should use, there is a good vuser calculator in our competitor's site. It's really good products. :-)