ASP.NET Mobile, Cookieless Sessions, and Load Balancing

[thinkfr33ly]

I have a WAP site powered by ASP.NET Mobile controls. We're using
cookieless sessions and have an F5 Load Balancer that balances the load
between two web servers.

Every once in a while we'll get the following exception:

System.FormatException: Invalid length for a Base-64 char array. at
System.Convert.FromBase64String(String s) at
System.Web.UI.LosFormatter.Deserialize(String input) at
System.Web.UI.MobileControls.MobilePage.LoadPageStateFromPersistenceMedium()
at System.Web.UI.Page.LoadPageViewState() at
System.Web.UI.Page.ProcessRequestMain()

We've configured our F5 to route all traffic to the same machine based
on the session ID in the URL. But what about the first request to the
site?

I suspect what's happening is this. The user's phone loads up the site
and the URL they load has no session ID in it because its the first
request. Any subsequent traffic has a session ID and so the F5 will
always send that traffic to the same machine.

But that machine isn't necessarily the same machine that issued the
original session ID! Since the first request was essentially routed
randomly to one of the two web servers, the F5 won't know to route
additional requests back to that same server since there was no session
ID in the first URL the user requested.

Does anybody agree with this assesment? Any suggestions on how to fix
it?

 

[Robbe Morris [C# MVP]]

Having zilch for experience with WAP sites and the F5 load balancer,
I cannot be 100% certain that this is the issue but...

If it happens periodically it may be that the ISP that
the mobile device runs its traffic through is running
their own outgoing traffic network proxy server. In PC
based browsers, this causes the load balancer to send
the request to the wrong server in the farm. I "suspect"
that this may be occurring to some of your users.

Purely a guess on my part.

If this is, in fact, the issue, there is a product
called ScaleOut StateServer that can remedy this.

http://www.eggheadcafe.com/articles/scaleout_server.asp

--
Robbe Morris - 2004/2005 Microsoft MVP C#

Earn money answering .NET Framework
messageboard posts at EggHeadCafe.com.
http://www.eggheadcafe.com/forums/merit.asp

 

[thinkfr33ly]

It turns out that this problem probably isn't due to load balancing.
After examining the log files I've determine that it only happens with
two phones.

These phones are the Motorola 8720 andthe Samsung SGH 427M.

There may be additional phones that cause this error, but we have yet
to see them hit the site.

Any ideas?