Setting cache dependencies
Cache dependencies allow the application to automatically clear cached data when related objects are modified.
The system uses dummy cache keys to create dependencies between cached data and other objects. Dummy keys are cache items without any data that represent objects or groups of objects. When an object is modified, the system “touches” the corresponding dummy keys, which causes the cache to delete all items that depend on the given dummy keys.
Sample scenario
A page with the /Products alias path displays a list of products (pages), which are placed as child items in the content tree. The product data is cached in the page’s code and has a dependency on the node|samplesite|/products|childnodes dummy key, which the system creates automatically.
When a visitor requests the Products page, the product data for the list is loaded from the database and stored in the content cache. If a child page of the Products page is modified, the dummy key is touched, and the cache deletes the dependent data.
The following table shows which dummy cache keys are touched when objects are modified:
Object type | Touched dummy keys | Sample dummy key values |
Pages | node|<site name>|<alias path>|<culture> + for all ancestors of the modified page: | node|samplesite|/home|en-us node|samplesite|/|childnodes |
Objects | <object type>|all Tip: You can find the object type values in the System application on the Object types tab. | cms.user|all |
Media files | mediafile|<guid> | mediafile|1ced44f3-f2fc- … |
Metafiles | metafile|<guid> | metafile|1ced44f3-f2fc- … |
Page attachments | cms.attachment|all | cms.attachment|all |
Page relationships | nodeid|<node id>|relationships | nodeid|5|relationships |
Settings | cms.settingskey|<settings key code name> cms.settingskey|<site id>|<settings key code name> Tip: You can find the setting key code name values in the Modules application by editing any module and opening the Settings tab. | cms.settingskey|cmspagedescriptionprefix |
Avatars | avatarfile|<guid> | avatarfile|1ced44f3-f2fc- … |
Custom table data records | customtableitem.<custom table code name>|all | customtableitem.customtable.sampletable|all |
Dependencies on form data records
The system currently does not touch any dummy cache keys when changes occur for data submitted via forms.
As a workaround, developers can prepare custom event handlers for BizFormItemEvents. Use the handler method to touch a custom cache key, and then enter the key into your cache dependencies. For example:
private void FormItem_InsertAfterHandler(object sender, BizFormItemEventArgs e)
{
// Touches a custom cache key, for example: "customformdata|bizform.contactus"
CacheHelper.TouchKey("customformdata|" + e.Item.BizFormClassName);
}
Adding custom cache dependencies
You can set custom cache dependencies when caching retrieved data or page output using the API. See Caching on MVC sites.
Create the dependencies by preparing a string with the names of dummy cache keys, and then call the CacheHelper.GetCacheDependency method on the string. The system automatically clears the related cache when the specified dummy keys are touched (i.e. when the corresponding objects are modified).
Example
Scenario: You have a page displaying a list of articles, and the code used to retrieve the article data uses the API for caching. You need to clear the cached article data whenever one of the article pages is modified.
Solution: When preparing the CacheSettings parameter in the code, add the nodes|<site name>|<article page type code name>|all dummy key as a cache dependency. The system touches this dummy key whenever any article page of the given type is updated.