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.
<configuration>
  <system.webServer>
    <httpProtocol>
      <customHeather>
        <add name="Arr-Disable-Session-Affinity" value="true" />
      </customHeather>
    </httpProtocol>
  </system.webServer>
</configuration>
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.
headers.Add(
     "Arr-Disable-Session-Affinity", 
     "True");

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

Comments

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 http://go.microsoft.com/fwlink/?LinkId=260882 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 …

Run native .NET application in Docker (.NET Framework 4.6.2)

Scope
The main scope of this post is to see how we can run a legacy application written in .NET Framework in Docker.

Context
First of all, let’s define what is a legacy application in our context. By a legacy application we understand an application that runs .NET Framework 3.5 or higher in a production environment where we don’t have any more the people or documentation that would help us to understand what is happening behind the scene.
In this scenarios, you might want to migrate the current solution from a standard environment to Docker. There are many advantages for such a migration, like:

Continuous DeploymentTestingIsolationSecurity at container levelVersioning ControlEnvironment Standardization
Until now, we didn’t had the possibility to run a .NET application in Docker. With .NET Core, there was support for .NET Core in Docker, but migration from a full .NET framework to .NET Core can be costly and even impossible. Not only because of lack of features, but also because once you…