How do I simulate transient errors with Azure Database?

Question

I am working with the Transient Fault Handling Application Block (TFHAB) to define a retry policy when interfacing with an Azure Database. I'm wondering if there is a way to invoke a throttling response in order to plan and handle likely production scenarios?

I could place an SQL command in a loop and run it until I invoke a response however presumably this is not considered to be "best practice"?

Can anyone suggest some practical ways in which I can test my transient error handling logic?

Answer 1

Look at combining Testing Transient errors in Azure and the list of error codes returned by Windows Azure SQL Database, and see if you can mock in the behavior that you are testing. Beyond unit testing I don't think that you are going to be able to 'simulate' errors because these errors are coming from SQL via the TDS protocol, which will be difficult to intercept. Your need would be a good candidate for a fork of the application block where you could inject a simulator.

Answer 2

I've managed to develop some code that allows you to reliably generate transient errors in Azure SQL Databases. You can find the code at: https://github.com/robdmoore/SQLAzureTransientDemo

Answer 3

My recommendation to you is dependency injection:) To eloborate, your higher level client code should not take a direct dependency to azure, put the client SDK behind an interface and pass that interface as dependency to your higher level client code. Pass the actual sdk for production code as the interface implementation and for your tests pass a test implementation of the interface where you can return any error code or response you want.