Wikimedia Bugzilla is closed!

Proposed solution for bug 38972:

pollForChanges should access the repo's wb_changes table using the "foreign wiki" facility implemented by mediawiki's LBFactory_multi. This is the way cross cluster database access is implemented for GlobalUsage, CentralAuth, etc.

(Tangent: the same mechanism could perhaps later be used to push changes to the job queue of multiple wikis).

The implementation is simple enough, once I261a2a31 is merged, there's hardly anything left to do. But the required setup of the load balancer is pretty complex and needs some investigation.