Sitecore Commerce 8.2 catalog cache details

July 11, 2019

For one of our Sitecore Commerce customers it is really important that product updates are processed and reflected on their website as soon as possible. In order to help them we really needed to understand where the product data is cached and how this is invalidated. In this post I will share our findings, which apply to Sitecore Commerce 8.2 & 8.2.1.

The catalog data is cached on the following levels:

Caching layers

Commerce Server

The catalog data is cached in the CatalogCache, which basically caches all the datasets that are retrieved from the database.

Sitecore Commerce Connect

Commerce connect has an ExternalIdCache and a TemplateHierarchyCache. The ExternalIdCache caches the mapping between the SitecoreId of a catalog item and the productid/categoryid. The TemplateHierarchyCache caches the sitecore templates which are generated based on the category and product definitions. Both of these are not important if mere product or catalog data has been changed.

Sitecore

The Sitecore data API caches the product data in the same way it does normal items, which is in the following caches:

  • ItemCache
  • DataCache
  • StandardValuesCache
  • PathCache
  • ItemPathsCache

Output cache

If the renderings on the page have caching enabled, the resulting output of those renderings will be cached in the output cache.

When cleared?

Items in the cache can have an expiration, meaning they will be refreshed when the items duration in the cache has exceeded the configured expiration. They can also be cleared by events that are trigged by certain actions in the system, publishing an item for example. Lastly, its possible to manually clear them by using the cache buttons in the commerce ribbon (Content editor).

Cache Expiration When cleared
CatalogCache Yes CommerceCacheRefreshEvent
ExternalIdCache No CommerceCacheRefreshEvent
TemplateHierarchyCache No CommerceCacheRefreshEvent
Sitecore data provider cache No Publish, CommerceCacheRefreshEvent
Output cache No Publish

Commerce Server

The commerce server catalog cache uses an expiration that is defined in the App_Config\CommerceServer\CommerceServer.catalog.config file. The catalog -> cache element contains several cache timeout attributes. See Cache Configuration Properties for more information.

Besides the expiration the entire catalog cache is cleared when a CommerceCacheRefreshEvent is queued in the EventQueue.

Sitecore data API cache

The Sitecore data API cache has no expiration and items are cached as long as they are valid (Based on published period). Specific items are removed from the cache when an ItemSavedEvent is queued in the EventQueue (This happens when the related items are published). This cache is also cleared when a CommerceCacheRefreshEvent is queued in the EventQueue.

Output cache

By default the renderings in the output cache have no expiration. The entire output cache is cleared when a publish action takes place. This is done by the Sitecore.Publishing.HtmlCacheClearer, Sitecore.Kernel event handler configured in the publish:end:remote event.

To make sure the output cache reflects the catalog changes in a timely fashion, this client has extended the output caching mechanism. They’ve added a VaryByProductData option that adds the product version to the generated cache key, similar to: http://www.sitecorecoding.com/2016/02/caching-rendering-html-when-conditional.html.

Clearing the output cache can have a serious impact on performance. It’s considered best practise to disable the event handler and periodically clear the HTML cache using the HtmlCacheClearAgent.

What is this CommerceCacheRefreshEvent you’ve mentioned?

The CommerceCacheRefreshEvent mentioned above is used to make sure that the related caches on all servers are cleared when a change is made on one of the servers. This event is essential for the commerce cache to stay consistent. This event is used to clear different types of caches. The event has a CacheType that can contain the following values:

  • “sitecore” - If the event also contains an ItemID, the invidual item is removed from the sitecore caches. If not, the entire sitecore cache is cleared.
  • “catalogcache” - The entire catalog cache is cleared and if the event also contains an ItemID, the invidual item is removed from the sitecore caches. If not, the entire sitecore cache is cleared.
  • “allcaches” - All sitecore and commerce caches are cleared
  • “commercecaches” - All sitecore and commerce caches are cleared, except for the catalog cache

When is this CommerceCacheRefreshEvent queued?

This event is queued when changes are made using the merchandising manager.

The event is also queued during an incremental index update. When items in the catalog are updated the CatalogIntervalAsynchronousStrategy will retrieve a list of modified catalog items from the ExternalId table. It will then queue a CommerceCacheRefreshEvent with CacheType catalogcache. This will make sure that the entire catalog cache is cleared on every server. After this, it will queue CommerceCacheRefreshEvent with CacheType sitecore and an ItemID for every catalog item, which makes sure that the catalog item is removed from the sitecore cache from every server.

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