Does iis recycle cleans memory? - asp.net

Question

I am having a web application deployed to IIS, my app uses static Dictionary which is filled in from an external api frequently.
Sometimes I observe that the Dictionary is being cleared once in a while & I suspect it is because of IIS Automatic Recycle.
Can anyone please confirm that this could be a reason?
So basically my question would be will IIS Recycle cleans up the static memory that a webapp is using? (Although I understand that this will only happens when there are no active connections to the server)

Answer 1

Yes, the IIS by default recycles your app pool by calling a garbage collector to clear the memory on every 20 minutes.
You can see Idle-timeout setting in your app pool -> Advanced settings, but better do not change it.
All static things are "Bad" do not use them, your option is caching. You can make a generic cache service that is using the default MVC cache and make it thread safe.
You can also use the [OutputCache] attribute on child actions controller and set minutes. Between this interval the data will be cached
Or you can implement your own caching logic.
From all the three things I will suggest you the first one with using the default MVC cache. I will provide you a sample implementation thanks to #TelerikAcademy and #NikolayKostov
namespace Eshop.Services.Common
{
using System;
using System.Web;
using System.Web.Caching;
using Contracts;
public class HttpCacheService : IHttpCacheService
{
private static readonly object LockObject = new object();
public T Get<T>(string itemName, Func<T> getDataFunc, int durationInSeconds)
{
if (HttpRuntime.Cache[itemName] == null)
{
lock (LockObject)
{
if (HttpRuntime.Cache[itemName] == null)
{
var data = getDataFunc();
HttpRuntime.Cache.Insert(
itemName,
data,
null,
DateTime.Now.AddSeconds(durationInSeconds),
Cache.NoSlidingExpiration);
}
}
}
return (T)HttpRuntime.Cache[itemName];
}
public void Remove(string itemName)
{
HttpRuntime.Cache.Remove(itemName);
}
}
}
The usage of it is super simple with anonymous function and time interval
You can set it as a protected property of a Base Controller and to Inherit BaseController in every controller you use. Than you will have the cache service in every controller and you can simply use it that way
var newestPosts = this.Cache.Get(
"newestPosts",
() => this.articlesService.GetNewestPosts(16).To<ArticleViewModel().ToList(),
GlobalConstants.DefaultCacheTime);
Let's assume that GlobalConstants.DefaultCacheTime = 10
Hope that this answer will be useful to you. :)

Answer 2

If you look at this MS article: https://technet.microsoft.com/pl-pl/library/cc753179(v=ws.10).aspx
In addition to recycling an application pool on demand when problems occur, you can configure an application pool to recycle a worker process for the following reasons:
At a scheduled time
After an elapsed time
After reaching a number of requests
After reaching a virtual memory threshold
After reaching a used memory threshold
So if IIS recycle would not clean up memory recycling it on memory threshold would not make sense. Additionally, IIS recycle cause application restart so it's obviously clears it memory too.