The Common Event Infrastructure in WebSphere Process Server

This is an overview of the Common Event Infrastructure as it is implemented in WebSphere Process Server.

The Common Event Infrastructure provides facilities for generation, propagation, persistence, and consumption of events, but it does not define the actual events. Instead, application developers and administrators define event types, event groups, filtering criteria, and correlation criteria.

An event occurs when something significant happens in the IT system. For example, an application processing a new customer order or a failure occurring in a critical part of the system. Information about the event is captured in an event object. This event object describes an event type, indicates when the application generated the event, and identifies properties that are relevant to the event.

The Common Event Infrastructure in WebSphere Process Server has the following components:

Common base event
The common base event component supports the creation of events and access to the property data of these events. Event sources use the common base event APIs to create new events that conform to the Common Base Event model. Event consumers use the APIs to read property data from received events. In addition, applications can convert events to and from XML text format, supporting interchange with other tools. The common base event component is part of the Eclipse-based Hyades environment.
Emitter
The emitter component supports the sending of events. After an event source creates an event and populates it with data, the event source submits the event to an emitter. The emitter optionally performs automatic content completion and then validates the event to ensure that it conforms to the Common Base Event specification. It also compares the event to configurable filter criteria. If the event is valid and passes the filter criteria, the emitter sends the event to the event server. An emitter can send events to the event server either synchronously (using Enterprise JavaBeans calls) or asynchronously (using a Java Messaging Service queue).
Event correlation spheres
An event correlation sphere is the scope that allows an event consumer to correlate events. Each event includes the identifier of the correlation sphere to which it belongs and the identifier of its parent correlation sphere from the event hierarchy. An emitter is provided (ECSEmitter class) that adds correlation data automatically to events.
Event server
The event server is the conduit between event sources and event consumers. The event server receives events that are submitted to emitters by event sources, stores events them in a persistent data store, and then distributes them asynchronously to subscribed event consumers. In addition, the event server supports synchronous queries of historical events from the persistent store.
Event catalog
The event catalog is a repository of event metadata. Applications use the event catalog to retrieve information about classes of events and the content of these events.
Event catalog application
Any application that stores or retrieves event metadata in the event catalog. This might be a management or development tool; it might also be an event source or event consumer.
Event source
Any application that uses an emitter to send events to the event server.
Event consumer
Any application that receives events from the event server. Event consumers process events outside the environment of the event source. Typically, these event consumers process events from a number of event sources.

Parent topic: What are events?


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