This should prevent having issues with hot key paths on entities that
experience a heavy WHOIS volume (e.g. contacts that registrars reuse on
many domains).
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=191506124
After investigating common domain create/update command usage
patterns by registrars, we noticed that it is frequent for a
given registrar to reuse both hosts (using a standardized set of
nameservers) as well as contacts (e.g. for privacy/proxy
services). With these usage patterns, potential per-registrar
throughput during high volume scenarios (i.e. first moments of
General Availability) suffers from hitting hot keys in Datastore.
The solution, implemented in this CL, is to add short-term
in-memory caching for contacts and hosts, analogous to how we are
already caching Registry and Registrar entities. These new
cached paths are only used inside domain flows to determine
existence and deleted/pending delete status of contacts and
hosts. This is a potential loss of transactional consistency, but
in practice it's hard to imagine this having negative effects, as
contacts or hosts that are in use cannot be deleted, and caching
would primarily affect widely used contacts and hosts.
Note that this caching can be turned on or off through a
configuration option, and by default would be off. We'd only want
it on when we really needed it, i.e. during a big launch.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=187093378
