Support mcrouter for broadcasting cross-DC purges.
There is gerrit repo, https://gerrit.wikimedia.org/r/#/admin/projects/mediawiki/services/python-cache-relay, which has the code that handles relaying purges for the WANObjectCache.
This should be ported to using Kafka and should support:
a) memcached purges
b) CDN (varnish) purges
MediaWiki should emit events as needed.