openstack team mailing list archive

[Caitlin Bestler <Caitlin.Bestler@xxxxxxxxxxx>]

Mark Nottingham asked:

>Why not just use
>   Cache-Control: no-cache?

>That way, intervening caches will do the right thing too...


Even with no caching anywhere you still have N replicas (typically three) that will be updated in an arbitrary order,
and clients that read from any one of those replicas.

Unless  you implement a draconian global locking scheme there is nothing you can do to prevent a client from reading
a copy that has just been rendered obsolete by another client completing the edit of the (N+1)/2th replica.

If the goal is to validate with all N servers then this should be a special transaction. The benefits of caching should remain
In place for typical reads.