We’ve been having intermittent problems causing users to be forcibly logged out of out application.
Our set-up is ASP.Net/C# web application on Windows Server 2003 Standard Edition with SQL Server 2000 on the back end. We’ve recently performed a major product upgrade on our client’s VMWare server (we have a guest instance dedicated to us) and whereas we had none of these issues with the previous release the added complexity that the new upgrade brings to the product has caused a lot of issues. We are also running SQL Server 2000 (build 8.00.2039, or SP4) and the IIS/ASP.NET (.Net v2.0.50727) application on the same box and connecting to each other via a TCP/IP connection.
Primarily, the exceptions being thrown are:
System.IndexOutOfRangeException: Cannot find table 0.
System.ArgumentException: Column ‘password’ does not belong to table Table.
[This exception occurs in the log in script, even though there is clearly a password column available]
System.InvalidOperationException: There is already an open DataReader associated with this Command which must be closed first.
[This one is occurring very regularly]
System.InvalidOperationException: This SqlTransaction has completed; it is no longer usable.
System.ApplicationException: ExecuteReader requires an open and available Connection. The connection’s current state is connecting.
System.Data.SqlClient.SqlException: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.
And just today, for the first time:
System.Web.UI.ViewStateException: Invalid viewstate.
We have load tested the app using the same number of concurrent users as the production server and cannot reproduce these errors. They are very intermittent and occur even when there are only 8/9/10 user connections. My gut is telling me its ASP.NET – SQL Server 2000 connection issues..
We’ve pretty much ruled out code-level Data Access Layer errors at this stage (we’ve a development team of 15 experienced developers working on this) so we think its a specific production server environment issue.
Lads, just as an update, it turned out that the problem was VMWare related under heavy usage – what a fun week! We’re changing the code around to suit the VMWare environment and we’ve seen some improvement already.
Thanks for the suggestions, I appreciate it.