around 11:30 UTC Nov 23 2018, wdqs updater crashed on all wdqs nodes. The updater is restarted by systemd a few times, but enters failed state once start limit is reached. The logs don't provide much information (see below).
Restarting the updater manually does not solve the issue, it goes back to failed after a number of attempts.
11:40:15.580 [update 8] INFO o.wikidata.query.rdf.tool.rdf.Munger - Weird reference http://www.wikidata.org/reference/5ff5d1308dcd060222a9dcea0a29de7f5828ed2c: unknown value http://www.wikidata.org/value/7e281616976c7de150357c18e76abfd1 for http://www.wikidata.org/entity/Q22089547 #logback.classic pattern: %d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n 11:40:39.662 [main] INFO o.w.q.r.t.change.ChangeSourceContext - Checking where we left off 11:40:39.666 [main] INFO o.w.query.rdf.tool.rdf.RdfRepository - Checking for left off time from the updater 11:40:40.070 [main] INFO o.w.query.rdf.tool.rdf.RdfRepository - Found left off time from the updater 11:40:40.071 [main] INFO o.w.q.r.t.change.ChangeSourceContext - Found start time in the RDF store: 2018-11-23T11:25:15Z 11:40:40.144 [main] INFO o.w.q.rdf.tool.change.KafkaPoller - Creating consumer wdqs1005 11:40:40.729 [main] INFO o.w.q.rdf.tool.change.KafkaPoller - Subscribed to 6 topics 11:40:40.730 [main] INFO o.w.q.rdf.tool.change.KafkaPoller - Set topic eqiad.mediawiki.page-undelete-0 to (timestamp=1542972315000, offset=140144) 11:40:40.730 [main] INFO o.w.q.rdf.tool.change.KafkaPoller - Set topic codfw.mediawiki.revision-create-0 to (timestamp=1542972315000, offset=56945679) 11:40:40.730 [main] INFO o.w.q.rdf.tool.change.KafkaPoller - Set topic codfw.mediawiki.page-undelete-0 to (timestamp=1542972315000, offset=6575) 11:40:40.730 [main] INFO o.w.q.rdf.tool.change.KafkaPoller - Set topic eqiad.mediawiki.revision-create-0 to (timestamp=1542972315000, offset=982852035) 11:40:40.730 [main] INFO o.w.q.rdf.tool.change.KafkaPoller - Set topic codfw.mediawiki.page-delete-0 to (timestamp=1542972315000, offset=409711) 11:40:40.731 [main] INFO o.w.q.rdf.tool.change.KafkaPoller - Set topic eqiad.mediawiki.page-delete-0 to (timestamp=1542972315000, offset=7485389) 11:40:42.883 [main] INFO o.w.q.rdf.tool.change.KafkaPoller - Found 927 changes 11:41:04.045 [update 0] INFO o.wikidata.query.rdf.tool.rdf.Munger - Weird reference http://www.wikidata.org/reference/f0241d2920c31202a1c72a60f2e154b44ffb7447: unknown value http://www.wikidata.org/value/054f90e140d6e4478605edbffbcb192e for http://www.wikidata.org/entity/Q2841515 11:41:04.434 [update 6] INFO o.wikidata.query.rdf.tool.rdf.Munger - Weird reference http://www.wikidata.org/reference/290275f5e6979162473e25b67ddf983812d47fc5: unknown value http://www.wikidata.org/value/054f90e140d6e4478605edbffbcb192e for http://www.wikidata.org/entity/Q388110