Donut Cache examples from Umbraco UK Festival talk "The need for speed"

DefaultController.cs

public class DefaultController : RenderMvcController
{
	[UmbracoDonutOutputCache(CacheProfile = "LongPageCache",
	Options = OutputCacheOptions.NoCacheLookupForPosts &
	OutputCacheOptions.ReplaceDonutsInChildActions, Order = 100)]
	public override ActionResult Index(RenderModel model)
	{
		return base.Index(model);
	}
}

Global.cs

public class Global : UmbracoApplication
{
	public override string GetVaryByCustomString(HttpContext context, string custom)
	{
		var result = base.GetVaryByCustomString(context, custom);
		if (string.IsNullOrEmpty(custom))
		{
			return result;
		}
		if (UmbracoContext.Current.IsFrontEndUmbracoRequest)
		{
			var keys = custom.Split(new[] { ";" }).ToList();
			if (keys.Contains("url"))
			{
				result += $"pageid={UmbracoContext.Current.PageId};";
				result += $"url={context.Request.Url}";
			}
		}
		return result;
	}
  }

UmbracoDonutOutputCacheAttribute.cs

public class UmbracoDonutOutputCacheAttribute : DonutOutputCacheAttribute
{
    
	public override void OnActionExecuting(ActionExecutingContext filterContext)
	{
        // overrides donut output cache attribute to not cache when in umbraco preview mode or Doctype grid editor preview
		this.Duration = -1;
		var previewMode = UmbracoContext.Current.InPreviewMode;
		if (!previewMode)
		{
			if (UmbracoContext.Current.HttpContext.Request.QueryString["dtgePreview"] == "1")
			{
				previewMode = true;
			}
		}
		if (previewMode)
		{
			this.Duration = 0;
		}
		base.OnActionExecuting(filterContext);
	}
}

UmbracoStartup.cs

public class UmbracoStartup : ApplicationEventHandler
{
	protected override void ApplicationStarting(UmbracoApplicationBase umbracoApplication,
		ApplicationContext applicationContext)
	{
		DefaultRenderMvcControllerResolver.Current.
			SetDefaultControllerType(typeof(DefaultController));
      
      PageCacheRefresher.CacheUpdated += this.PageCacheRefresherCacheUpdated;

	}
  
  private void PageCacheRefresherCacheUpdated(PageCacheRefresher sender, CacheRefresherEventArgs e)
	{
		switch (e.MessageType)
		{
			case MessageType.RefreshById:
			case MessageType.RemoveById:
				var contentId = (int)e.MessageObject;
				var doctype = string.Empty;
				var item = UmbracoContext.Current.ContentCache.GetById(contentId);
				if (item != null)
				{
					doctype = item.DocumentTypeAlias;
				}
				this.ClearPageOutputCache(contentId, doctype);
				break;
			case MessageType.RefreshByInstance:
			case MessageType.RemoveByInstance:
				var content = e.MessageObject as IContent;
				if (content == null)
				{
					return;
				}
				this.ClearPageOutputCache(content.Id, content.ContentType.Alias);
				break;
		}
	}
    
    private void ClearPageOutputCache(int contentId, string doctype)
	{
		var enumerableCache = OutputCache.Instance as IEnumerable<KeyValuePair<string, object>>;

		if (enumerableCache == null)
		{
			return;
		}

		// get all output cache keys that contain current page id
		var keysToDelete = enumerableCache
			.Where(x => !string.IsNullOrEmpty(x.Key) && x.Key.Contains($"pageid={contentId};"))
			.Select(x => x.Key);

		// remove all caches for current page
		foreach (var key in keysToDelete)
		{
			OutputCache.Instance.Remove(key);
		}

		 var manager = new OutputCacheManager();

		 manager.RemoveItems("MasterSurface","Footer");

		 if(doctype == "NewsDetail")
		 {
			// clear cache of all news related actions
			manager.RemoveItems("NewsSurface");
		 }

	}
}

Web.config

<system.web>
	<caching>
		<outputCache enableOutputCache="true" />
		<outputCacheSettings>
			<outputCacheProfiles>
				<add name="LongGlobalCache" duration="86400" />
				<add name="LongPageCache" duration="86400" varyByCustom="url" />
				<add name="LongUserPageCache" duration="86400" varyByCustom="url;user" />
				<add name="NoCache" duration="0" />
			</outputCacheProfiles>
		</outputCacheSettings>
	</caching>
 </system.web>

This is great Dave thanks, it'll make a big difference for how I handle caching. One thing - I'm finding that IsFrontEndUmbracoRequest is returning true even if the request comes from opening the node in the backoffice. Do you see the same?

How will you cache the header and footer in this scenario? Do u add a custom cache attribute with a different profile on them?

varyByCustom="url;user" can cause cause problems when parsing cache keys as ; is the default delimiter for any other MVC routes that will also be stored in the key.

This will create a key that looks like this: url;user=pageid=1;url=/your-url;somethingelse=somethingelse; etc.