How does IIS handles multiple simultaneous requests to a web service using the same session id when that web service relies on sessions?
If the first web service call has not finished processing, does IIS queue the second web service call temporarily until the first web service call has finished (since they both rely on the same session data).
Or does IIS allow both requests to go forward and any changes made to the session store by the first request immediately affect the second web service call in process even thought that may cause unexpected results.
I believe it is using the first option by queuing the second call until the first is completed due to session reader\writer locks but I have not been able to locate a definitive answer.
Note: In this case the web service requests are generated from the client browser asynchronously.
Yes, like anything else that’s using session state, the session state module is going to block the request from going any further down the pipeline (i.e. executing your ASMX web method) until it can aquire the lock to the session. Session state is the enemy of concurrency, avoid it at all costs.