tl;dr
Ignore this email if you do not use MediaWiki event streams.
On Monday December 11 2023, all MediaWiki related event streams will
have artificial
canary events
<https://wikitech.wikimedia.org/wiki/Event_Platform/EventStreams#Canary_Events>
injected into them. If you use any of these streams, you should discard
these canary events.
*Add code to your consumers that discards events where* meta.domain ==
"canary".
Canary Events
At WMF, we use artificial 'canary' AKA 'heartbeat' events
<https://wikitech.wikimedia.org/wiki/Event_Platform/Stream_Configuration#canary_events_enabled>
to differentiate between a broken event stream and an empty event stream.
Canary events should be produced at least once an hour. If there are no
events in a stream for an hour, then something is likely broken with that
stream.
These artificial canary events can be identified by the fact that their
meta.domain field is set to "canary". If you use any of the streams listed
below, you will need to add code that discards any events where meta.domain
== "canary".
Back in 2020, we began producing canary events into all new streams, but we
never got around to enabling these for streams that already existed. We
needed to ensure that all consumers of these streams filtered out the
canary events. We're just finally getting around to enabling canary events
for all streams.
We will enable canary event production
<https://phabricator.wikimedia.org/T266798> for the following streams on
Monday, December 11th, 2023:
- mediawiki.recentchange
- mediawiki.page-create
- mediawiki.page-delete
- mediawiki.page-links-change
- mediawiki.page-move
- mediawiki.page-properties-change
- mediawiki.page-restrictions-change
- mediawiki.page-suppress
- mediawiki.page-undelete
- mediawiki.revision-create
- mediawiki.revision-visibility-change
- mediawiki.user-blocks-change
- mediawiki.centralnotice.campaign-change
- mediawiki.centralnotice.campaign-create
- mediawiki.centralnotice.campaign-delete
If you consume any of these streams, either external to WMF networks using
EventStreams, or internally using Kafka, please ensure that your consumer
logic discards events where meta.domain == "canary" before this date. (Note
that not all of these streams are exposed publicly at
stream.wikimedia.org
<https://stream.wikimedia.org/?doc#/streams>.)
Thank you,
-Andrew Otto & the WMF Data Engineering team
<https://wikitech.wikimedia.org/wiki/Data_Engineering>
References
- T266798 - Enable canary events for all MediaWiki streams
<https://phabricator.wikimedia.org/T266798>
- T251609 - Automate ingestion and refinement into Hive of event data from
Kafka using stream configs and canary/heartbeat events
<https://phabricator.wikimedia.org/T251609>