Effe (pr. e-ff-y) connects your frontend javascript applications to your backend Event Driven Architecture (EDA). Effe is a framework-agnostic event hub providing a familiar event bus interface for your front-end components combined with an extensible connector interface to enable events to flow between your backend hosted server components and the front-end EventHub.
The implementation is a pure EventHub implementation with clear responsibilities. EventHub has a single purpose - to transmit events to subscribed callbacks for each channel when a message is published. A Subscriber may subscribe to ALL messages published on the EventHub by subscribing to the wildcard channel "*".
The Connector participates in the EventHub pub/sub mechanism by subscribing to one or more channels to receive events, it may also use the wildcard channel "*" to receive all events published on the EventHub. The EventHub has no knowledge the connector exists and you can have as many connectors as you wish participating in the Pub/Sub eco-system to build complex connected apps which deliver events via different channels. Connectors have a simple responsibility - for each event received via the subscribed callback or callbacks (there may be many) package up the event data and transmit it to its Connection. Likewise the connector may also publish events to the EventHub when data is received (if the connector is a bi-directional style connector). In this way the Connector is the Bridge between the pub/sub EventHub and the external event source.
We like to think of this setup as EventBridge for your FrontEnd Web Apps.
This implementation maintains a clear separation of responsibilities. Connectors are simply Pub/Sub participants who have a special job - to connect the EventHub to an external server or source. This could be anything at all - WebSockets, Momento Topics, an API, AWS EventBridge, Kafka Topics, event other EventHubs! - anywhere you need to connect your events. You can create multiple connectors to handle events from your EventHub in many different ways. We love the Pub/Sub model and think it simplifies your Front-End to no end.
GO wild - connect your events to everything!
- WebUI subscribes to a channel to receive events from the EventHub using a callback function.
- EventHub calls subscriber callbacks for any channel for each event that is published
- Connector is connected to the EventHub and subscribes to one or more channels (implementation dependent).
- WebSocket connector also connects to a websocket server and is responsible for reformatting the EventHub events to the correct format for the WebSocket protocol being used.
- WebSocket Connector also listens to the websocket for messages coming back and for each message will reformat them into a compatible EventHub message.
- The WebSocket Connector will publish the reformatted event to the channel identified in the message completing the end to end communication loop.
Important Note: Websockets do not implement publish/subscribe patterns, they enable transportation of data from a client to the server using a negotiated Sub-protocol which determines the data which flows between them. This is why we have created the IConnector Interface - to enable connections to servers using any kind of transport mechanism you need - like WebSockets - these are a Connector. You can implement the connectors any way you like - it's up to you how you connect your EventHubs.