Continuations

Yesterday I spent quite few time trying to solve some problem related to old data stored in the webapp session. It made me remember a similar situation few years ago, when I had hard time with the same problem (not that it just happened twice, but those two times were quite remarkable).
But there is a small difference between those two situations, a small difference that makes all the difference.

In the early days I was dealing with a kind of application similar with those online selling: a lot of pages that you must commit the information only at the end. So the use of the session, although not mandatory is almost 100% of the choice. But the application of yesterday is the opposite: it should commit the changes all the time, almost at every breath of the user; but again we are using the session.

I remember myself thinking how it would be nice and simple to get free of the session, all those synchronization problems, back button problems and so on. And now I have an application that could act like saving all the time, but still we are stick with the session. Why?

Well I don't have the answer but I guess it is just a question of old habits, justified by the performance of using the session. And that is my point: is the session the best high performance solution?

Well, I would like to have numbers about it (maybe in a future post), but it is well spread the idea that session is an enemy to scalability. It makes all the sense, but a non-session world looks like to be impossible outside of the books.

I do not advocate about killing the session, no!, but a better management of it is crucial for: a better performance application (memory leak can kill an application more easily than a slow response time) and a smooth programming (spend hours trying to find out why things do not match is not nice).

As I said in the beginning, it is just a way home though, but it deserves some kind of investigation, what the world thing about this subject. Despite of the REST way of doing things (which we can discuss later) I have found a nice third wave, something that they claim to be Statefull programming model for a stateless world: Continuations.

I would explain it here, but there is nice article at IBM which can do this job much better Crossing borders: Continuations, Web development, and Java programming.

I hope you enjoy the reading; maybe it could make you less angry next time (knowing that there is a brighter life out there).