Strange Behavior in a Web Farm (Network Load Balancing)

G

gfergo

We have a pretty straightforward page ('Page 1'). The codebehind
creates a DataTable and binds the data to a Repeater which renders an
HTML table on screen. The first column in the HTML table is a
Checkbox.

When one or more boxes is/are checked, and the submit button is
clicked, the page posts back to itself, the selected value(s) is/are
stored in a cookie, the user is then redirected to a second page
('Page 2').

Most of the time the second page ('Page 2') renders correctly. The
correct behavior is to query a database, create a DataTable, 'filter'
the DataTable using the value(s) stored in the cookie, and generate an
HTML table displaying the rows that are found.

Sometimes -- and so far ONLY when the site is being served by 2 or
more web servers -- the second page ('Page 2') renders and the HTML
table is missing (looks like the DataTable contains no data).

Since this only seems to happen when the site is being served by 2 or
more web servers (NLB Web Farm) we are assuming the user must have
bounced from Server A to Server B.

The only thing that stands out (code-wise) is this:

The HTML table is part of a user control (.ascx file). The user
control is accessing a Page Property (marked public). The user
control does this by (a) Checking whether the containing page is a
subclass of a specific Type, (b) casting the Page as that Type, and
(c) accessing the Property.

If the user bounced from Server A to Server B, could the Type be
different in some way?

NOTES:

- We are using a cookie
- We are not using the ASP.NET Session object
- The data is retrieved by both 'Page 1' and 'Page 2' from the
database -- not from cache
- The machine key (in the machine.config file) is the same on both
servers

Anyone have any thoughts on this?

Thanks!

Glen J Fergo
Lead Web Developer, Henry Schein, Inc.
(e-mail address removed)
 

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