We are currently using a lesser known tool called eValid for our load testing of a web app. This tool uses a separate browser per user instead of a virtual user. One big problem that we ran into is that eValid uses a shared cache pool to handle cookies. This means that for a transaction to succeed, it will need to keep the cookie all the way until the transaction is completed. In this case after step 1 in our load test, eValid will try to grab a cookie from this shared cache pool that could have originated from another browser user and this is causing our app to error out. We have ruled out this problem being a load balancer issue.
Shared cookies!?! This flies in the face of the concept of multiple user performance testing with distinct sessions. Are you sure that there isn't a way to set it up to use individual cookies? I would be sure to run this by the vendor... or ask for my money back.
A problem is a difference between what is perceived and what is desired, that
we want to reduce (Dewey 1933)
We verified with the vendor that they do indeed use a shared cache pool. They are asking us to now make changes to our load test environment to hopefully get this to work. I have a feeling it may be difficult to ask for our money back at this point.
I remember using a non-standard web-testing tool a LONG time ago which used a kind of shared cache, but you could configure the path to the cache for each vuser, e.g. c:/cache/<VUID>. Sounds strange that a multi-user test tool cannot support individual session cache... Defeats the purpose somewhat. HTH