See the email today from Yun Mao. This is a proposal to have a pluggable
framework for integration services that maintain memberships. This was
originally desiged to replace the MySQL heartbeats in Nova, although there will
be a mysql-heartbeat backend by default as a drop-in replacement. There is a
zookeeper backend in the works, and we've discussed the possibility of building
a backend that can poll RabbitMQ's list_consumers.

This is useful for more than just Nova's heartbeats, however. This will largely
supplant the requirement for the matchmaker to build these backends in itself,
which had been my original plan (the matchmaker is already in openstack-common).
As such, it had already been my intent to have a MySQL-backed matchmaker. The
only thing new is that someone has actually written the code.

In the first pass, the intention is to leave the matchmaker in and introduce the
membership modules. Then, the matchmaker would either use the new membership
modules as a backend, or even replaced entirely.