Wikimedia is releasing a new service: EventStreams[1].  This service allows us to publish arbitrary streams of JSON event data to the public.  (Psssst: we’re looking for cool new uses[2] to put on an upcoming blog post.)

Initially, the only stream available will be good ol’ RecentChanges.  This event stream overlaps functionality already provided by irc.wikimedia.org and RCStream.  However, this new service has advantages over these (now deprecated) services.

1. We can expose more than just RecentChanges.

2. Events are delivered over streaming HTTP (chunked transfer) instead of IRC or socket.io.  This requires less client side code and fewer special routing cases on the server side.

3. Streams can be resumed from the past.  By using EventSource, a disconnected client will automatically resume the stream from where it left off, as long as it resumes within one week.  In the future, we would like to allow users to specify historical timestamps from which they would like to begin consuming, if this proves safe and tractable.

I did say deprecated!  Okay okay, we may never be able to fully deprecate irc.wikimedia.org.  It’s used by too many (probably sentient by now) bots out there.  We do plan to obsolete RCStream, and to turn it off in a reasonable amount of time.  The deadline iiiiiis July 7th, 2017.  All services that rely on RCStream should migrate to the HTTP based EventStreams service by this date.  We are committed to assisting you in this transition, so let us know how we can help.

Unfortunately, unlike RCStream, EventStreams does not have server side event filtering (e.g. by wiki) quite yet.  How and if this should be done is still under discussion.

The RecentChanges data you are used to remains the same, and is available at https://stream.wikimedia.org/v2/stream/recentchange. However, we may have something different for you, if you find it useful. We have been internally producing new Mediawiki specific events[3] for a while now, and could expose these via EventStreams as well.

Take a look at these events, and tell us what you think.  Would you find them useful?  How would you like to subscribe to them?  Individually as separate streams, or would you like to be able to compose multiple event types into a single stream via an API?  These things are all possible.

I asked for a lot of feedback in the above paragraphs.  Let’s try and centralize this discussion over on the mediawiki.org EventStreams talk page[4].   In summary, the questions are:

• What RCStream clients do you maintain, and how can we help you migrate to EventStreams?

• Is server side filtering, by wiki or arbitrary event field, useful to you?

• Would you like to consume streams other than RecentChanges?  (Currently available events are described the event-schemas repository.)