Re: PHP session replication

Hi. Just for comparison: PHP does not provide sessions in the same way a servlet-based platform provides. PHP actually destroys the in-mem representation of sessions after each request is served, whereas a servlet-based platform caches the sessions in mem between requests. ASP.Net also serializes session state, but not into a cookie - it uses a hidden field instead. Which works around cookie size limitation. You don't even have a choice of database sessions with ASP.Net. OTOH, even if performance might suffer, scalability, as far as the sessions mechanism is concerned, is excellent - you don't need session replication. Servlet-based platforms provide the most complicated solution, when compared to the other two. They keep sessions in mem, which improves performance (no serialization/deserialization for each request), but creates potential scalability problems. You won't hit the wall at a few thousands of users, but replicating maybe a million sessions among no more than a hundred servers causes the replication process to consume quite a lot of resources, the resources being used for replication increasing faster than linearly with each added server (not quite exponentially, though). You can use sticky sessions with most servlet-based platforms, but these come with their own problems (already described by a previous poster). Nevertheless, in mem sessions a la servlets are a very convenient mechanism to use - the session replication is provided by the platform, and the app programmer doesn't have to worry about it. All three approaches rely on every piece of data in the session being serializable, so you can't store interesting objects, like an open file or the like, in sessions. Does anybody know of any fundamentally different session sharing/replication mechanism? br, flj