EventBlabla what?! So Many Event* services. This page disambiguates, and links to their more extensive documentation.
In all of the following, an 'event' is defined as a structured and schema-ed data object. The data object is usually serialized as JSON with the schema specified in and validated with JSONSchema.
EventLogging is the original event framework used by WMF. It consists of 3 main parts.
The EventLogging python codebase consists of various services that can be mixed and matched to consume, validate, transform, and produce streams of JSON events between different endpoints. EventLogging was originally created for Mediawiki analytics purposes, but was also used to support production streams of events via an HTTP eventlogging-service used for the EventBus service.
For the original analytics EventLogging use case, all schemas are maintained and stored on meta wiki. The default EventLogging validation logic looks for matching schemas in this online http/wiki repository.
The EventLogging Mediawiki extension is used by Mediawiki to send JSON data to EventLogging by sending a GET request with query parameter encoded JSON data to a special Varnish endpoint. Requests to this Varnish endpoint are logged (via varnishkafka), and make their way into downstream EventLogging services.
Like EventLogging, 'EventBus' refers to a few different pieces of infrastructure. More detail can be found on the EventBus documentation page.
This is the Mediawiki extension responsible for sending events from WMF Mediawiki installations to backend event intake service (EventGate).
As of 2019-09 eventlogging-service-eventbus has been decommissioned in favor of EventGate
This is a particular deployment of eventlogging-service that is used to accept internally produced events over HTTP. It is configured to use JSONSchemas from the mediawiki/event-schemas repository to validate incoming events.
Event Schema Repositories and HTTP Service
Our event schemas are available via an HTTP API at https://schema.wikimedia.org/. This site simply hosts up to date schemas stored in git repositories.
WMF has 2 event schema git repositories. schemas/event/primary is for production/tier 1 events. Schemas here are more tightly controlled (and bikeshed). schemas/event/secondary is for non critical and analytics focused events.
Previously, schemas also lived in the mediawiki/event-schemas repository, but this has been deprecated in favor of schemas/event/primary.
You can learn more about WMF's Event Schemas at Event_Platform/Schemas.
EventGate is the event service replacement for eventlogging-service-eventbus, a component of the Modern Event Platform program. This service has the same API as eventlogging-service-eventbus, with a few updated expectations for the event schemas it can process. Over 2019-2020, we will be replacing all eventlogging intake services with EventGate deployments.
While planning the Modern Event Platform program, product managers and engineers expressed a desire to be able to more dynamically configure the behavior of clients producing (and potentially consuming) event streams. EventGate also needs some dynamic configuration in order to enforce that specific event streams only include events of the same JSONSchema lineage. The EventBus extension (as well as other event producing clients) need a way to configure the destination event service (EventGate) instance where they should produce an event.
The EventStreamConfig MediaWiki extension was built to support these use cases. It uses MediaWiki's configuration to centralize the event stream configuration for all of these clients. It exposes both a PHP MediaWiki interface as well as a HTTP API to look up configs for event streams by name. The EventLogging extension uses the PHP API to load stream configuration to browser clients via ResourceLoader.
EventStreams is a public facing service. It exposes streams of events via HTTP SSE/EventSource. This service replaced the Mediawiki RecentChange specific service RCStream, and perhaps eventually will also deprecate irc.wikimedia.org.
Modern Event Platform
The Modern Event Platform Program is about unifying the our analytics and production event systems into a generic event stream intake, validation and processing systems.