Read last executed SQL statement from a memory dump

In this post I’m going to show you how to diagnose SQL exceptions using memory dumps. Imagine you have a web application deployed on a production server. Your application is using Elmah configured to log all exceptions to a dedicated table. One day you receive information that users are unable to make orders and in the Elmah log there are lots of SqlTypeExceptions:

SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM.
 at System.Data.SqlClient.TdsParser.TdsExecuteRPC(_SqlRPC[] rpcArray, Int32 timeout, Boolean inSchema, SqlNotificationRequest notificationRequest, TdsParserStateObject stateObj, Boolean isCommandProc, Boolean sync, TaskCompletionSource`1 completion, Int32 startRpc, Int32 startParam)
 at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite)
 at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean asyncWrite)
...

No more information available. If you are using NHibernate you may turn on SQL logging but, if you have thousands of users, this will have a negative impact on the application responsiveness. Another idea might be to use ADO.NET ETW logs – even though this way we will minimize the performance drop, it’s still not a perfect solution. ETW logs weigh hundreds of MB and contain a tremendous amount of information, which you need to filter and analyze. I plan to write about this type of logging in the future. For now, let’s take a third approach: create a production memory dump when the application breaks and analyze it locally in the debugger.

Adplus: handling managed exceptions

In this post I’m going to concentrate on managed exceptions and the ways how we can handle them using Adplus. Some time ago John Robbins in his Bugslayer column wrote a great article about handling specific managed exceptions using Adplus. Although the general concept of the managed exception hasn’t changed (and so the SOS commands) his scripts do not work with the latest installation of Adplus. With the version 6.12 of the Debugging Tools for Windows we received a brand new version of Adplus (7th) which was transformed from a VB script to a .NET application. Although the command line options seems to be compatible with the previous version, the configuration file structure changed significantly. Old scripts need to be rewritten in order to work with the new version. In this post I will not only upgrade John Robbin’s scripts but also show you some (I hope interesting) new features of Adplus.