Private update status cache system

Functions to manage the update status cache.

We specifically do NOT use the core cache API for saving the fetched data about available updates. It is vitally important that this cache is only cleared when we're populating it after successfully fetching new available update data. Usage of the core cache API results in all sorts of potential problems that would result in attempting to fetch available update data all the time, including if a site has a "minimum cache lifetime" (which is both a minimum and a maximum) defined, or if a site uses memcache or another pluggable cache system that assumes volatile caches.

The Update Manager module still uses the {cache_update} table, but instead of using cache_set(), cache_get(), and cache_clear_all(), there are private helper functions that implement these same basic tasks but ensure that the cache is not prematurely cleared, and that the data is always stored in the database, even if memcache or another cache backend is in use.

File

core/modules/update/update.module, line 580

Handles update checking for Backdrop core and contributed projects.

Functions

Name	Location	Description
_update_cache_set	core/modules/update/update.module	Stores data in the private update status cache table.
_update_cache_get	core/modules/update/update.module	Retrieves data from the private update status cache table.
_update_get_cache_multiple	core/modules/update/update.module	Returns an array of cache items with a given cache ID prefix.
_update_cache_clear	core/modules/update/update.module	Invalidates cached data relating to update status.
update_flush_caches	core/modules/update/update.module	Implements hook_flush_caches().
update_admin_bar_cache_info	core/modules/update/update.module	Implements hook_admin_bar_cache_info().
update_config_info	core/modules/update/update.module	Implements hook_config_info().