Web browsers communicate with Web Servers using HTTP.HTTP does not provide tools that can track users and data in the context of a web session.Also, last thing I need when my server is loaded is to start repair and data shuffling.It is possible to run a distributed cache without trouble if you do lot of monitoring and hand holding to make sure nodes are not loaded.Zope’s session management makes use of name-spaces like cookies, HTTP form elements, and/or parts of URLs “in the background” to keep track of user sessions.Which of these name-spaces are used is configurable using the browser_id manager (described later).Session data is valid for the duration of a configurable inactivity timeout value or browser shut-down, which ever comes first.Zope’s session management keeps track of anonymous users as well as those who have Zope login accounts. Data maintained by Zope’s session management is no more secure than HTTP itself.
Most our customer deployment are clusters they always need high availability and sometimes scalability. Trick is that all nodes in the system have to agree on what nodes are in the system. To solve the above problem, you need to maintain a group communication system. Maintaining a membership group means lot of trouble. First problem that that they do not scale very well. Second problem is that when a node has failed, other nodes will detect that and remove the node from the group. When a node is presumed dead, other node reshuffle the data.The extended session ID format will be part of the URL if URL rewriting is activated, and the startup flag is set to true.You can specify an interval of time after which HTTP sessions expire.In other words, servlets have built in session tracking.  Yes, we do feel a little like the third grade teacher who taught you all the steps of long division, only to reveal later how you could use a calculator to do the same thing.But we believe, as your teacher probably did, that you better understand the concepts after first learning the traditional approach.