event-driven-microservices

Event-Driven Pipeline: Emit, Process, Project, Notify

In an event-driven architecture, an event is emitted, processed to update state, projected onto a read model, and fanned out to subscribers. This workflow makes that pipeline explicit: emit the event with a unique ID, process it (e.g. "order_updated"), update the read model projection, and notify subscribers (billing, shipping, analytics).

Workflow

eventType, payload, source
            |
            v
+------------------+     +---------------------+     +--------------------------+     +--------------------------+
| edm_emit_event   | --> | edm_process_event   | --> | edm_update_projection    | --> | edm_notify_subscribers   |
+------------------+     +---------------------+     +--------------------------+     +--------------------------+
  eventId generated        result: "order_updated"    projectionUpdated: true          count: 3
  timestamp set            subscribers: [billing,                                      (billing, shipping,
                           shipping, analytics]                                         analytics)

Workers

EmitEventWorker -- Emits an event of eventType from source. Returns a unique eventId and a timestamp.

ProcessEventWorker -- Processes the event. Returns result: "order_updated" and the subscribers list: ["billing", "shipping", "analytics"].

UpdateProjectionWorker -- Updates the read model. Returns projectionUpdated: true.

NotifySubscribersWorker -- Notifies all 3 subscribers. Returns count: 3.

Tests

8 unit tests cover event emission, processing, projection updates, and subscriber notification.

Running

See ../../RUNNING.md for setup and execution instructions.