Charlie, Like Dave Watts said, session replication is hit-or-miss depending on the application, the user load, the server architecture, the network architecture, etc.
Typically, I recommend thinking about what kind of data you need to replicate and can you put that data in a cookie as a backup for if/when a server crashes instead of Java server level session replication. Can you rely on only a userID (or a reference to a userID)? Maybe if you cache some data, you can persist the way you found the data (such as search parameters) instead of the data itself. For low load and small sessions, you can wddx your entire sessions up into a database. It's a complicated thing, and it always takes a different for each application. I would say you have a plethora of options, el guapo. I hope I've helped. -- nathan strutz http://www.dopefly.com/ On 10/23/07, Charlie Griefer <[EMAIL PROTECTED]> wrote: > > Hey all... > > up front, i'm not a server guy. just a code monkey :) > > with that disclaimer out of the way... got a question about load > balancing and failover of cf servers. > > as i understand it... > > there is the concept of "sticky sessions", where all requests by a > particular user "stick" to a particular machine in the cluster. in > theory, this balances the load over the servers. but if one server > were to go down, all users on that server would subsequently go down > with the ship (so to speak). so you have load balancing, but not > failover. > > in a situation where you don't implement sticky sessions, various > requests from a given user would be bounced around from machine to > machine. this way the load balancing remains intact, and if a single > machine in the cluster fails... nobody knows (they're just not bounced > to that particular machine). the problem in this situation is... > session variables. a user gets bounced from machine to machine, but > their session does not. > > it's this session variable issue that i'm trying to explore/solve. at > a previous job, we used a product called "Coherence" from tangosol > (now owned by Oracle) (see > http://www.tangosol.com/coherence-overview.jsp). the coherence box > acts as a dedicated session variable repository in the cluster... so > requests can be bounced from server to server and still have access to > session variables. > > seems to be a viable product... but i'm trying to do the necessary due > diligence in exploring all of the options. we haven't moved to CF8 > yet (still on CF7), but I had heard that CF8 would actually have this > functionality built in (the ability to use sessions in a clustered > environment). quick googling tho seemed to indicate that this was an > "expensive" process and not necessarily recommended (?) > > can anyone shed any light on how to handle this situation? i know we > can move to client vars and use a db for client variable storage... > but i'd prefer to stick with session variables if at all possible. > > thanks! > > -- > Charlie Griefer > > ================================================ > "...All the world shall be your enemy, Prince with a Thousand Enemies, > and whenever they catch you, they will kill you. But first they must catch > you, digger, listener, runner, prince with a swift warning. > Be cunning and full of tricks and your people shall never be destroyed." > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| Get involved in the latest ColdFusion discussions, product development sharing, and articles on the Adobe Labs wiki. http://labs/adobe.com/wiki/index.php/ColdFusion_8 Archive: http://www.houseoffusion.com/groups/CF-Talk/message.cfm/messageid:291884 Subscription: http://www.houseoffusion.com/groups/CF-Talk/subscribe.cfm Unsubscribe: http://www.houseoffusion.com/cf_lists/unsubscribe.cfm?user=89.70.4
