Commit 74c45340 authored by alexpott's avatar alexpott

Issue #2541432 by Wim Leers: Follow-up for #2231595: Document why...

Issue #2541432 by Wim Leers: Follow-up for #2231595: Document why ChainedFastBackend cannot use BackendChain
parent 8f9ece97
......@@ -569,6 +569,9 @@
* $settings['cache']['default'] = 'cache.custom';
* @endcode
*
* Finally, you can chain multiple cache backends together, see
* \Drupal\Core\Cache\ChainedFastBackend and \Drupal\Core\Cache\BackendChain.
*
* @see https://www.drupal.org/node/1884796
* @}
*/
......
......@@ -20,6 +20,8 @@
* to ensure fast retrieval on the next request. On cache sets and deletes, both
* backends will be invoked to ensure consistency.
*
* @see \Drupal\Core\Cache\ChainedFastBackend
*
* @ingroup cache
*/
......
......@@ -39,6 +39,15 @@
* Because this backend will mark all the cache entries in a bin as out-dated
* for each write to a bin, it is best suited to bins with fewer changes.
*
* Note that this is designed specifically for combining a fast inconsistent
* cache backend with a slower consistent cache back-end. To still function
* correctly, it needs to do a consistency check (see the "last write timestamp"
* logic). This contrasts with \Drupal\Core\Cache\BackendChain, which assumes
* both chained cache backends are consistent, thus a consistency check being
* pointless.
*
* @see \Drupal\Core\Cache\BackendChain
*
* @ingroup cache
*/
class ChainedFastBackend implements CacheBackendInterface, CacheTagsInvalidatorInterface {
......
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