id	summary	reporter	owner	description	type	status	priority	milestone	component	version	severity	resolution	keywords	cc
23448	Passive invalidation via last_changed should use timestamps	westi	ryan	"For #23173 we are switching lots of things over to passive invalidation via cache incrementors and last_changed.

This includes switching the oldest thing we had using this method of invalidation over to using {{{wp_cache_incr}}}.

This ticket is a petition to use {{{time()}}} still as the initial value so as to avoid race conditions with cache evictions and cache incrementors.

Currently with a 1 based last_changed key the following is possible with a persistent object cache backend like memcache:

 * last_changed is set to 1
 * list of pages is cached with 2 pages being the result of a get_pages call
 * last_changed is evicted from the memcache server
 * Another page is added
 * A call to get_pages happens, sets last_changed to 1 and returns the old data

Confusion the reigns for a bit until other things are evicted or another change is made.

If we start with {{{last_changed = time()}}} then we have no danger of using stale cache entries."	defect (bug)	closed	high	3.6	Cache	trunk	major	fixed	has-patch