Skip to main content

How you can deactivate session affinity on Azure Web App and ARR

In today's post we will talk about REST API and stick sessions.

Nowadays, REST API and Web Services are very common. We can find a lot of system and devices worldwide that are using HTTP(s) protocol and REST Services to communicate.
It not very common to send a cookie or session information when you calling a REST endpoint. All information are send in the heather, but not like cookies or session data.

In this situation you may want to disable sending cookies and session information to the clients. In this way you could use a little less resources on backend. Especially when you have a system that will need to manage hundreds of thousands of messages per second.
This two things can be manage and disabled pretty easily.

Going further, let's analyze what is happening when you host an endpoint like this on Azure like a Web App. It is important to know that in front of a Web App on Microsoft Azure we have out of the box a Load Balancer when multiple instances are deployed for the same Web App.
Behind this Load Balancer you will have of course an ARR (Application Request Routing). This feature is inherited from ISS - is one of the coolest extension of ISS.
ARR will keep track of different request. Once a request ends on a specific instance, the ARR will make sure that all other requests from the same client will hit the same instance of Web App.
This feature is important for application where there are session sensitive data or you have stateless connections. In this scenario you will always want to end up on the same instance.

But of course, not all the time you will need something like this. This feature is great when you need it. In most of the cases you will not need it. For this scenario, we can disable ARR to manage the session affinity.
The most easy solution is to set this configuration from web.config file, like below.
        <add name="Arr-Disable-Session-Affinity" value="true" />
There is another option, to set it from code, but it will require a deployment. Personally, I prefer to keep this kind this configuration in configuration files, where you can easily spot and change.

In this way we can reduce a little bit the stress that is on ARR system.


Popular posts from this blog

How to check in AngularJS if a service was register or not

There are cases when you need to check in a service or a controller was register in AngularJS.
For example a valid use case is when you have the same implementation running on multiple application. In this case, you may want to intercept the HTTP provider and add a custom step there. This step don’t needs to run on all the application, only in the one where the service exist and register.
A solution for this case would be to have a flag in the configuration that specify this. In the core you would have an IF that would check the value of this flag.
Another solution is to check if a specific service was register in AngularJS or not. If the service was register that you would execute your own logic.
To check if a service was register or not in AngularJS container you need to call the ‘has’ method of ‘inhector’. It will return TRUE if the service was register.
if ($injector.has('httpInterceptorService')) { $httpProvider.interceptors.push('httpInterceptorService&#…

ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded

Today blog post will be started with the following error when running DB tests on the CI machine:
threw exception: System.InvalidOperationException: The Entity Framework provider type 'System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer' registered in the application config file for the ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See for more information. at System.Data.Entity.Infrastructure.DependencyResolution.ProviderServicesFactory.GetInstance(String providerTypeName, String providerInvariantName) This error happened only on the Continuous Integration machine. On the devs machines, everything has fine. The classic problem – on my machine it’s working. The CI has the following configuration:

TeamCity.NET 4.51EF 6.0.2VS2013
It seems that there …

Entity Framework (EF) TransactionScope vs Database.BeginTransaction

In today blog post we will talk a little about a new feature that is available on EF6+ related to Transactions.
Until now, when we had to use transaction we used ‘TransactionScope’. It works great and I would say that is something that is now in our blood.
using (var scope = new TransactionScope(TransactionScopeOption.Required)) { using (SqlConnection conn = new SqlConnection("...")) { conn.Open(); SqlCommand sqlCommand = new SqlCommand(); sqlCommand.Connection = conn; sqlCommand.CommandText = ... sqlCommand.ExecuteNonQuery(); ... } scope.Complete(); } Starting with EF6.0 we have a new way to work with transactions. The new approach is based on Database.BeginTransaction(), Database.Rollback(), Database.Commit(). Yes, no more TransactionScope.
In the followi…