This patchset implements caching lookup and reverse-lookup
functions to allow for much faster retrieval of encrypted data
from Barbican, which doesn't currently support batched
requests in its Secrets API.
This behavior is necessary since Deckhand has to potentially
retrieve and store up to dozens of secrets per request. Note
that data for both lookup functions are invalidated
together, as they are tied to the same cache.
This change implements caching around arguably the most
expensive operation in Deckhand: encryption. By
caching encryption itself, the performance of rendering
documents thereby increases in a meaningful way, without
having to implement much logic to pull it off.
A follow up patch set here: https://review.openstack.org/#/c/585842
focuses on caching rendered documents themselves.
Change-Id: I0d330690a3c5e899b763ddcaa00d356007aa23fb
3af01d63d5