We are looking for a simple way to add redundancy to a web app.
We are concerned about session cookies.
If we just put each server on a round robin DNS service, will that be sufficient at least for our beta release or will session cookies be a big issue?
I'm guessing that the user caches the DNS of the server and in such a case I would expect that problems are rare. But I could imagine that when they are on the site for over 15 minutes (assuming the DNS refresh is set to 15 minutes) then it will cause big problems.
IDEALLY: Is there a round robin DNS service that is designed for failover and will always redirect the same IP to the same server?
As a work-around, we are thinking: Since we have a centralized database, we centrally save all session data. Then, when a user without a session cookie is found, we check if it exists and log them in.