sessions on servers with fallover
Posted on 2006-07-20
I'm working on a large project at the moment that will eventually be run on multiple servers (round robin) and some servers will have fallover to a second server. When the user visits the site they are given a session id from the server, say for example that the server now died and the other server took over on the same ip address. The user then loads another page on the server (not realising that its just fallen over to another server), the browser will send the session id to the server.
My question is - what happens next ?!?
From what I can work out there are only 3 options -
1) the server ignores the session id from the browser and gives it a new one
2) the server takes on the session id from the browser and re-creates the session on the server using that id
3) there is an error (probably given by the server saying "invalid session id".
I imagine this same thing happens with firefox lots as the sessionsaver plugin saves the session id, and then gives it back to the browser next time you view that page ? , so the server has to deal with the session id being different than the one it wants to give then.
I'd think this would be the same on all servers/clients - but I need the answer for both Firefox and IE, and the server is running apache2 and php5 (or will be by the time we get the fallover in place !).