ExternalService

Interface to an external service.

External services must be carefully managed in reactive Skip services to make sure that dependencies are properly tracked and data from external systems is kept up to date.

Context.useExternalResource accepts the name of an external service, which must be associated to an instance of this ExternalService interface by SkipService.externalServices.

Custom implementations of the ExternalService interface can be defined as needed, and the Skip framework provides several out of the box: SkipExternalService and PolledExternalService in the @skipruntime/helpers package, and integrations with other systems such as PostgreSQL and Kafka in @skip-adapter/* packages.

If it is a Skip service, then SkipExternalService can be used, specifying an entrypoint. The external Skip service will update its resources reactively and those changes will propagate through this service.

If it is not a Skip service, then PolledExternalService can be used to specify the external source and desired polling frequency.

Methods

shutdown()

shutdown(): Promise<void>

Shutdown the external service.

Returns

Promise<void>

---

subscribe()

subscribe(
   instance, 
   resource, 
   params, 
   callbacks): Promise<void>

Subscribe to a resource provided by the external service.

Parameters

Parameter	Type	Description
instance	string	Instance identifier of the external resource.
resource	string	Name of the external resource.
params	Json	Parameters of the external resource.
callbacks	{ error: (error) => void; update: (updates, isInit) => Promise<void>; }	Callbacks to react on error/update.
callbacks.error	(error) => void	Error callback to log the error that prevent an idermetiate update.
callbacks.update	(updates, isInit) => Promise<void>	Update callback.

Returns

Promise<void>

---

unsubscribe()

unsubscribe(instance): void

Unsubscribe from a resource provided by the external service.

Parameters

Parameter	Type	Description
instance	string	Instance identifier of the external resource.

Returns

void