On 2018-01-09 the wikidatawiki database will move from its current home on the "s5" slice to a brand new "s8" slice. The wikidatawiki.{analytics,web}.db.svc.eqiad.wmflabs and wikidatawiki.labsdb DNS service names will be updated to point to the new slice host by system administrators. This change should not affect most users of the Wiki Replica servers.
Only applications that are connecting to s5.{analytics,web}.db.svc.eqiad.wmflabs or s5.labsdb and expecting the wikidatawiki_p database to be present will be affected. These applications should update their configuration to connect to the new "s8" slice instead.
This is the end point (or nearly so) of a large amount of work that has been done by Wikimedia's fabulous DBA team of Jamie and Manuel to improve the health of the Wikidata wiki. See https://phabricator.wikimedia.org/T177208 for more details.
Bryan