Transient Fault Handling with SQL Azure and Entity Framework step by step guide

Communication errors are always a pain!! When you are working with cloud platform like Azure, communication errors makes you feel the pain even more!!

Thanks that Transient Fault Handling framework exists!!

Alright guys, so here I am going demonstrate how to configure transient fault handling application block of Enterprise Library 6 (and above hopefully, if they don’t change in next versionsJ) with SQL Azure and Entity framework. This going to be a long article that is what I think. So be ready!!

What are Transient Faults or Transient Errors?

These are mainly network issues. If you perform an operation in Azure and sometimes it does not work however if you try after some time, it works well. This odd and non-predictable behavior is nothing but transient faults.

When we talk about SQL Azure, transient faults are common. The article Azure SQL Database Resource Management - http://msdn.microsoft.com/library/azure/dn338083.aspx mentions the scenarios in which you may face transient fault of SQL Azure.  I highly recommend you to go through the all this documents and related links. Very informative!!

Now, very common transient error of SQL Azure is throttling.

What is throttling?

Throttle is very common term used in computing and networking. The dictionary meaning of throttle is to kill or stop something. Throttling can be of any type like, network throttling, bandwidth throttling, and email throttling and so on.  Throttling can be sometime good and sometime bad. When it is bad for you, it is your responsibility to handle it. Throttling is good when the database server engine is experiencing extreme load and it is well above the desired load. Then throttling brings down consumption of resource and frees some of the load of database engine. This is done via blocking the connections or denying the new connections to SQL Azure database engine. It is bad when you are trying to connect to SQL Azure and throttling occurs and you get connectivity errors with SQL Azure. To understand more about SQL Azure throttling refer to the link - http://msdn.microsoft.com/en-US/library/azure/dn338079.aspx.

Solution -

The solution is simple and you are advised to implement retry logic in your application. To implement retry logic in SQL Azure and entity framework, we use Transient Fault Handling block. It is simple and recommended to always use Transient Fault Handling framework to deal with SQL Azure connectivity errors and have retry logic in application.

Implementation –

Please note that, I am using Transient Fault Handling Block version 6.0.1304. This is the one available as of today (7^th July 2014). Also I am using Azure SDK 2.3 and visual stiudio 2013 for this sample.

First let’s create a server in SQL Azure and add a database in it. I created simple database named as Company and added only one table in it named as Customer with 3 columns and sample data as shown in below screenshot.