PlaceholderingRenderCache

Adds automatic placeholdering to the RenderCache.

This automatic placeholdering is performed to ensure the containing elements and overarching response are as cacheable as possible. Elements whose subtree bubble either max-age=0 or high-cardinality cache contexts (such as 'user' and 'session') are considered poorly cacheable.

Automatic placeholdering is performed only on elements whose subtree was generated using a #lazy_builder callback and whose bubbled cacheability meets the auto-placeholdering conditions as configured in the renderer.config container parameter.

This RenderCache implementation automatically replaces an element with a placeholder:

• on render cache hit, i.e. ::get()
• on render cache miss, i.e. ::set() (in subsequent requests, it will be a cache hit)

In either case, the render cache is guaranteed to contain the to-be-rendered placeholder, so replacing (rendering) the placeholder will be very fast.

Finally, in case the render cache item disappears between the time it is decided to automatically placeholder the element and the time where the placeholder is replaced (rendered), that is guaranteed to not be problematic. Because this only automatically placeholders elements that have a #lazy_builder callback set, which means that in the worst case, it will need to be re-rendered.

Hierarchy

• class \Drupal\Core\Render\RenderCache implements RenderCacheInterface
  • class \Drupal\Core\Render\PlaceholderingRenderCache

See also

sites/default/default.services.yml

File

core/lib/Drupal/Core/Render/PlaceholderingRenderCache.php, line 40

Namespace

Drupal\Core\Render

Members