The extension backend is organized into several different, largely independent services, each responsible for their own external communications and data persistence.
In contrast to the architecture preferred by simple web services — a single REST interface synchronously managing data per request — this architecture prefers services that are constantly monitoring, indexing, and caching data, pushing the results to data stores and UI asynchronously.
Grouping business rules and control flow into these services means
- Explicit dependencies provided via service constructors
- Consistent asynchronous startup and teardown procedures
- Namespacing and data migrations per service, rather than a single global data store. This pattern offers flexibility and resilience at the expense of more data management logic.
- Clear boundaries for testing system behavior in the future
Service APIs are designed to
- Expose emitted events to the rest of the system asynchronously via
Service().emitter - Expose common external requests via public methods on the
Serviceobject - Resolve inter-service dependencies with
Promises