Considerations for Caching Sitecore Content Pages (HTML markup)

Question

I've read the documentation regarding caching and also a number of posts on SSE and I'm trying to understand if there is anything else to consider other than the following when enabling caching for a page by turning off the DisableBrowserCaching option:

• Personalisation - of any components on any of the pages we wish to Cache
• Content changes - If we have dynamic content (which we do)

As I understand it by default Sitecore pages are not cached due to the dynamic nature of Sitecore pages it is unlikely that the data source, device, authentication status, user, rendering parameters and/or query string parameters are the same as a previous request.

Therefore instead caching should really be set on specific components instead.

We are looking to cache a number of key/high-traffic pages only (e.g the homepage) for 1 or 2 minutes as most of the components on this page are dynamic so are not cached by Sitecore - but we are happy that the content might be a minute or two out of date for the performance gains we might get for a full page cache.

Other than the content not being immediately up-to-date (if updated in Sitecore or from a 3rd party) is there anything else to think about or side-affects to be aware of?

Further info: We are not using Personalisation at all currently. Sitecore 8.1 update 2.

Answer 1

When I was in a similar situation, what I did was to create a custom cache key and extended it off of the VaryByData cache option for renderings.

What you can do then is to based on the dynamic properties that makes your dynamic contents (UserGroupId, Affiliate, etc...) you can generate a cache just for that situation. In the example below, based on the info in the visitors cookie, we cache the renderings differently. This caches the output (HTML) of the rendering.

The code

using Sitecore;
using Sitecore.Data;
using Sitecore.Data.Items;
using Sitecore.Mvc.Pipelines.Response.RenderRendering;
using Sitecore.Mvc.Presentation;

namespace Customer.Mvc.Theme.Pipelines.mvc.renderRendering
{
    public class GenerateCacheKey : Sitecore.Mvc.Pipelines.Response.RenderRendering.GenerateCacheKey
    {
        protected override string GenerateKey(Rendering rendering, RenderRenderingArgs args)
        {
            var cacheKey = base.GenerateKey(rendering, args);

            if (rendering.RenderingItem.ID == new ID(Constants.Renderings.Product.ProductGrid))
            {
                var caching = rendering.Caching;

                var cookie =
                    System.Web.HttpContext.Current.Request.Cookies[
                        Foundation.Constants.Strings.AffiliationCookieName];

                if (caching.VaryByData && !string.IsNullOrWhiteSpace(cookie?.Value))
                {
                    cacheKey += "_#affiliateId:" + cookie.Value;
                }
            }

            return cacheKey;
        }
    }
}

The Config

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">
  <sitecore>
    <pipelines>
      <mvc.renderRendering>
        <processor patch:instead="processor[@type='Sitecore.Mvc.Pipelines.Response.RenderRendering.GenerateCacheKey, Sitecore.Mvc']"
                     type="Customer.Mvc.Theme.Pipelines.mvc.renderRendering.GenerateCacheKey, Customer.Mvc.Theme"/>
      </mvc.renderRendering>
    </pipelines>
  </sitecore>
</configuration>

Answer 2

I would never use DisableBrowserCaching as it will cache media files on browser, nothing to do with html pages.

For Sitecore driven content, we should leverage HTML Caching on renderings with relevant Vary By options. While using it, take care for below things:

1. Define HTML cache Size as per its utilization. Use the /sitecore/admin/cache.aspx or /sitecore/admin/stats.aspx to know the utilization.
2. Choose the Vary By option wisely. Refer - [http://www.xcentium.com/blog/2016/09/23/sitecore-caching-and-how-it-works-in-mvc-solutions][1]
3. Never cache renderings which needs postbacks, if you use so, post backs won't work.
4. Make sure HTML Cache is getting cleared on every publish. It gets cleared on publish:end:remote event on CD servers.

While using Dynamic Content, never apply Sitecore caching on renderings. Try to use .NET Time based cache to serve dynamic content. So that the cache will be cleared after provided internal of time automatically. See below example -

Cache.Insert(cacheKey, response, null, System.DateTime.Now.AddMinutes(10), TimeSpan.Zero, System.Web.Caching.CacheItemPriority.NotRemovable, null);