Our memcache install recently started removing keys, and we're not sure why. Large groups of keys vanish at the same time.
Memcache reports that evictions are low to non-existent, and our app has no way to clear memcache (it can only delete specific keys). Even keys of which the app has no knowledge get deleted, so we're pretty convinced they're getting expired. However, our memcache configuration hasn't been touched in some time.
Has anyone debugged an issue like this before, and if so, are there any steps you'd recommend we take? How flexible is memcache's expiration policy - is it possible that we're suddenly running into a criterion based on (say) write frequency to a key?