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When Session Variables Go Bad - Cap'n. The Resources. They Canna Take It!

LACanadian

Cap'n. The Resources. They Canna Take It!

Forgetting about the threading issues, there are a number of less esoteric issues that impact the use of Session variables. The strain on server memory can get quite high, depending on the usage of your web site.

As we mentioned earlier, Session variables are implemented as a collection. Actually, as a collection of Variants. This means that for every session, you not only have the data being stored, but also the implementation of the Add, Remote, Item and Count methods, as well as the IEnum interface. Then, since it is a collection of variants, the collection also needs to implement the IEnumVariant interface. Finally, the values in the collection are tied together using a linked list. So if you add even a small piece of data to the session variables, the memory usage might seem way out of whack.

Now in the connectionless world of HTTP, there is no way for the application to know when a user is done with their session. So IIS implements a session timeout mechanism. By default, it is twenty minutes, but it can easily be configured by the web site administrator. This value does significantly impact the resource usage of the web server. Let's say that you get 1000 users an hour on your site. That means that, on average, you will have 330 sessions active (okay, 333, but the math is easier if there are zeros). Say each session takes up 4KB of space. That means that 1.3 MB would be constantly allocated on the server. Not a problem, you say? Fine. So long as you keep ratcheting up the server memory as your site becomes more popular.

I am the owner of a small application development consulting company that specialized in the design and implementation of Internet-based applications. While there are others who can make a web site look good, our expertise is in making the site function. This includes infrastructure design, database design and administration, software development and deployment. For the most part, we utilize Microsoft-based languages and tools. And we are skilled enough to have generated two patent applications for our clients.

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  • Give Alternative for Session

    Posted by arshad3108 on 14 Jan 2004

    Hi Bruce,
    Your Article is informative, but you [b]missed the core point [/b] in explaining what will be the Alternative for Session variables in a Distributed Server Environment. I have used sessio...

  • xml?

    Posted by ark2000 on 23 Jan 2003

    for tker

    Could you point us to some examples? That sounds like a good challange!

  • Posted by MarioF on 04 Sep 2002

    [quote][1]Posted by [b]Nigorr[/b] on 27 Apr 2002 02:53 AM[/1]
    So what should we all be using instead. If we can't use cookies, because essientially seesion things use cookies how are you suppose to ...

  • Re: What to Use Instead

    Posted by LACanadian on 08 May 2002

    Whenever I have created a high-traffic, browser-neutral site, I have maintained session information stored in a database. In other words, when a user logs into the site, they are assigned a 32-charac...

  • Why not use XML?

    Posted by tker on 05 May 2002

    In response to the question of what to use instead, is there any reason not to use XML files (identified via a querystring of the filename) that are stored on the server to track user state? We've bee...