Nathan Andelin skrev:
From: Thorbjoern Ravn Andersen
Frequently it is too many idle sessions which must time out to be reclaimed. First try lowering the session timeout value.

Could you expand on that? My Google search on session timeout values returned results for terminal services and other specific applications, but not Web Application Servers, generally.
Naturally.

Originally the http-servers were stateless meaning that there was no concept of "this request goes to user A who was here just earlier etc". Cookies was invented to get around that - it is basically a token identifying a user. This has been used in many web frameworks to implement sesisons, basically a memory structure for holding user specific information across requests.

The problem with these sessions are:

1) the structure is in memory
2) a busy site may serve MANY sessions
3) users do not log out, they just stop clicking on the site

=> loaded webserver application needs LOTS of memory and eventually crash or swap to death.

One way to approach this, is to kill idle sessions. The idle period is what is referred to above as the "session timeout" value. A typical value is 30 minutes. Lowering this, will help you somewhat but not much when the load is intense.

Another approach used AFAIK in Apache Tomcat and other Java web servers is to persist the oldest sessions to disk (basically freezing them) and unfreezing them when the user comes back. This allows users to come back the day after and still have their shopping cart items in their cart. This is very nice and easily done in Java where objects can be serialized to a file and unserialized back into an object.

But all this is just part of the solution. Basically a web application must be built from the beginning to be scalable. The only way to be sure it IS scalable is to do scalability tests. Otherwise your users will be doing that when the system goes live and they are not very forgiving.

Note that the scalability tests should simulate users, not programmers, as programmers use the system nicely :)

Hope this clarifies things somewhat...


As an Amazon Associate we earn from qualifying purchases.

This thread ...

Follow-Ups:
Replies:

Follow On AppleNews
Return to Archive home page | Return to MIDRANGE.COM home page

This mailing list archive is Copyright 1997-2024 by midrange.com and David Gibbs as a compilation work. Use of the archive is restricted to research of a business or technical nature. Any other uses are prohibited. Full details are available on our policy page. If you have questions about this, please contact [javascript protected email address].

Operating expenses for this site are earned using the Amazon Associate program and Google Adsense.