Ceph » rgw

RGW is supposed to implement read-after-write consistency, but it often does not.

(03:19:57 PM) Tv: cmccabe: i think it goes like this; most of AWS docs are written before the read-after-write stuff came up; the spec is mostly silent about this
(03:20:22 PM) Tv: cmccabe: aws implementation routed write actions to master copy of data, others saw possibly laggy read-only replicas
(03:21:00 PM) Tv: cmccabe: huge customer demand made them add "read-after-write", that is cache invalidation, to you never see stale reads
(03:21:08 PM) Tv: cmccabe: that transition is complete for only some regions
(03:21:31 PM) Tv: cmccabe: they are definitely moving toward read-after-write, and that's what we should implement (that's already been agreed on)
(03:21:50 PM) Tv: cmccabe: but in this case, it seems our request routing is 100% random, that is, worse than aws ever was
(03:21:53 PM) Tv: cmccabe: or something
(03:22:07 PM) Tv: i don't actually know where if anywhere rgw has caching
(03:22:13 PM) Tv: or whether it touches non-primary replicas ever
(03:22:45 PM) Tv: cmccabe: let me explicit about this, one more time: we've already decided to go for "read-after-write"