Architecture
Fiori’s architecture connects a browser-based UI5 front-end to the SAP backend through OData services, usually via a Fiori front-end server (embedded or hub). Understanding this stack explains how apps work and where issues arise.
A user opens an app in the launchpad; the UI5 app calls its OData service (through the gateway) which runs the backend logic/CDS and returns JSON; the app renders it.
- In an embedded deployment the front-end server runs on the S/4HANA system itself (common, simpler).
- UI (SAPUI5/Fiori): the app running in the browser.
- Fiori launchpad & front-end server: hosts the launchpad, apps and the Gateway/OData layer.
- Watch out: Confusing embedded and hub setups.
The layers
- UI (SAPUI5/Fiori): the app running in the browser.
- Fiori launchpad & front-end server: hosts the launchpad, apps and the Gateway/OData layer.
- OData services: the RESTful interface exposing backend data.
- Backend (S/4HANA/ABAP + CDS): the business logic and data.
Embedded vs hub
In an embedded deployment the front-end server runs on the S/4HANA system itself (common, simpler). In a hub deployment a separate front-end server serves Fiori for one or more backends (better isolation and for multi-system landscapes). The choice affects setup, upgrades and security.
How a request flows
A user opens an app in the launchpad; the UI5 app calls its OData service (through the gateway) which runs the backend logic/CDS and returns JSON; the app renders it. Most Fiori issues, missing tiles, "service not available", no data, map to a specific layer in this chain.
Common pitfalls
- Confusing embedded and hub setups.
- Inactive OData service breaking an app.
- Not tracing the request layer when debugging.