Blog posts by Tobias2020-08-25T06:10:59.0000000Zhttps://world.optimizely.com/blogs/tobias/Optimizely WorldUsing the ASP.Net Async SessionState Module together with Episerver Visitor Groups<p>The<span> </span><a href="https://devblogs.microsoft.com/aspnet/introducing-the-asp-net-async-sessionstate-module/">ASP.Net Async SessionState Module</a><span> </span>has several benefits over the older default one as it is fully async.</p>
<p>To use it in an Episerver site is mostly plug and play, just follow the instructions on Microsoft dev blog and your are good to go. There is one scenario I have found were it doesn't work and that is with Visitor Group criterias that use the session as a storage of state. When registering the session-based criterias they look for the default session state module and if it cannot find it, the criterias will not work. One of these criteras is Landing URL / starting URL, which is used for determining what page on the site the user first visited.</p>
<p>In order to support the Async module we will have to basically redo what Episerver has done, but switch out the default module for the Async module.</p>
<p>First we create a<span> </span><code>IInitializationHttpModule</code><span> </span>and in it we initialize our own State storage handler, as Episervers'<span> </span><code>VisitorGroupStateStorageHandler</code><span> </span>only works for the default session stage module.</p>
<pre class="language-csharp"><code>/// <remark> Taken from Epis VisitorGroupHttpInitialization, to support SessionStateModuleAsync </remark>
[InitializableModule]
public class AsyncVisitorGroupHttpHandler : IInitializableHttpModule
{
private AsyncVisitorGroupStateStorageHandler _storageHandler;
public void Initialize(InitializationEngine context)
{
}
public void Uninitialize(InitializationEngine context)
{
}
public void InitializeHttpEvents(HttpApplication application)
{
Create().Initialize(application.Modules, CriterionEvents.Instance);
}
private AsyncVisitorGroupStateStorageHandler Create()
{
if (_storageHandler == null)
{
_storageHandler = new AsyncVisitorGroupStateStorageHandler();
}
return _storageHandler;
}
}</code></pre>
<p><span>Now we create or state storage handler. Here the important part is that we go through all modules registered and find the </span><code>SessionStateModuleAsync</code><span> module so we can hook into session start event. The Visitor group criteria will listen to this, among other events, and for example store the landing URL of the user.</span></p>
<pre class="language-csharp"><code>/// <remark> This is taken from Epis own implementation of VisitorGroupStateStorageHandler, but made to support SessionStateModuleAsync </remark>
public class AsyncVisitorGroupStateStorageHandler
{
static ILogger _log = LogManager.GetLogger(typeof(AsyncVisitorGroupStateStorageHandler));
public void Initialize(HttpModuleCollection application, ICriterionEventsRaiser instance)
{
var sessionModule = (SessionStateModuleAsync) application.AllKeys.Select(k => application[k])
.SingleOrDefault(module =>
module is SessionStateModuleAsync);
if (sessionModule != null)
{
sessionModule.Start += (sender, args) =>
{
instance.RaiseStartSession(sender,
new CriterionEventArgs(new HttpContextWrapper(HttpContext.Current)));
};
}
else
{
_log.Warning("No SessionStateModuleAsync found, criterias relying on session state will not work");
}
}
}</code></pre>
<p><span>With this code in place we should now see our visitor groups working as intended.</span></p>2020-08-25T06:10:59.0000000ZBlog post