New creates a new provider engine, operating on the provided network channel, and accepting requests for entities from a node within the set obtained by applying the provided selector filter.

DefaultEntityRequestCacheSize is the default max message queue size for the provider engine.

DefaultRequestProviderWorkers is the default number of workers used to process entity requests.

Engine is a generic provider engine, handling the fulfillment of entity requests on the flow network.

RetrieveFunc is a function provided to the provider engine upon construction.