Losing Session State with ASP.NET/SQL Server

Question

I have a ASP.NET MVC workflow configured as two websites managed by a load balancer. The websites use Sql Server as the session state provider and have authentication switch off (its not required).

Now, sporadically I appear to be losing session state, and I believe this is because the request is being handled by the alternative server, so essentially the user is jumping from server to server, depending how the load balancer sees fit. I am not always "losing session state" at the same stage in the workflow, so I believe it is something related to the web farm configuration + sql server session state.

Both applications use the same machine key to encrypt and decrypt session state stored in sql server.

The configuration on both servers is as follows:

<authentication mode="None" />
<sessionState mode="SQLServer" sqlConnectionString="{connection-string}" />
<machineKey decryptionKey="777CB456774AF02F7F1AC8570FAF31545B156354D9E2DAAD" 
            validationKey="89B5B536D5D17B8FE6A53CBB3CA8B8695289BA3DF0B1370BC47D362D375CF91525DDB5307D8A288230DCD4B3931D23AED4E223955C45CFF2AF66BCC422EC7ECD" />

I've confirmed that this is identical on both servers, is there something I am missing?

This does not occur in my development environment when I am using a single server.

I fear I am suffering from the Friday blues, and no doubt will figure out the answer next week, sadly I don't want to wait!

Any ideas?

Answer 1

Found the issue.

When you create applications that you expect to share session state using Sql Server, they need the same ID configured in IIS. This is because the session ID that is generated is generated based on the application ID. (Internally the application ID is something like LM/W3SVC/1

The two servers had different IDs for each application in IIS. The resolution is to change the ID under `Manage Website -> Advanced Settings' on each server.

Answer 2

1. Using IIS Manager, double-check your machine key settings at both the root and website levels.

2. Review the IsolateApps modifier on the machine key element - http://msdn.microsoft.com/en-us/library/w8h3skw9%28v=vs.100%29.aspx

3. Did you recently upgrade from 3.5 to 4.0?

4. Last resort - recycle the appPools on both machines, and restart IIS.

Answer 3

Sessions have (web) application scope. See if this MS KB helps.

Update: Interesting down vote. Perhaps my suggestion needs more clarity.

In addition to matching machine keys, you also have to match the IIS configuration for sites (so it's the "same application" (application path) in IIS.