Best way to keep a list in a wcf service memory

Question

I have a web application with a login system which uses a wcf service. The user type his username/password to login, then we create a unique token for the user and then the token is saved in the browser cookies to keep the user online. Everytime the user send a request, his token is sent along with the request. We keep all the tokens in a basic List in the service memory. Now, I'm asking myself if it is the best way to do this. Will iis recycle my app memory? I have read this question about keeping a list in a wcf service and it looks like I should avoid using a list in memory. What is the best alternative to this?

Thanks

Answer 1

Yes, if the App Pool housing your WCF Service is recycled, you will lose everything you've cached in memory, so you will also need a persistence fallback (eg RDBMS or NoSql database) which will be re-loaded on resumption.

You don't say what you want stored along with the token. If its just the string token, then a HashSet<string> might be best, and if there is other data, then a ConcurrentDictionary<string, Whatever> would work best.

Assuming that as users login / logout of your service that the token collection will need to be mutated, which means that concurrency issues need to be considered, (you've got that with the ConcurrentDictionary )

And you'll also need to consider the effects of stale tokens - you'll want to remove / delete unused tokens (memory and database).