ISO knowledge of zone.detached()

[tgrecojs]

I'm currently utilizing the zone API to establish a durable zone that I can refer to when creating a setStore, mapStore, etc. This method of store creation seemingly matches my use-case—at least, that's the assumption I've made. Upon encountering the use of detached in the router implementation found in @agoric/network, I realized my knowledge regarding the use of zone.detached() was nonexistent, thus leading me to open this discussion.

Below is the code from the @agoric/network that led me to create this.

agoric-sdk/packages/network/src/router.js

Lines 108 to 138 in c74c628

	export const prepareRouterProtocol = (zone, powers, E = defaultE) => {
	const detached = zone.detached();
	const makeRouter = prepareRouter(zone);
	const makeNetworkProtocol = prepareNetworkProtocol(zone, powers);
	const makeRouterProtocol = zone.exoClass(
	'RouterProtocol',
	M.interface('RouterProtocol', {
	registerProtocolHandler: M.call(
	M.arrayOf(M.string()),
	M.remotable(),
	).returns(),
	unregisterProtocolHandler: M.call(M.string(), M.remotable()).returns(),
	bind: M.callWhen(Shape.Endpoint).returns(Shape.Vow$(Shape.Port)),
	}),
	() => {
	/** @type {Router<Protocol>} */
	const router = makeRouter();
	/** @type {MapStore<string, Protocol>} */
	const protocols = detached.mapStore('prefix');
	/** @type {MapStore<string, Remote<ProtocolHandler>>} */
	const protocolHandlers = detached.mapStore('prefix');
	return {
	router,
	protocolHandlers,
	protocols,
	};

I'm curious to understand more about zone.detached(), how stores cultivated with detached zones differ from those shaped with the top-level setStore, mapStore, and the circumstances in which it would be apt to opt for one technique over the other.

Keywords: zone, setStore, mapStore, storage

[dckc]

@michaelfig help me out here? what does detached() do?

[michaelfig]

Using the top-level mapStore, etc, creates a singleton store that is assigned to the label (here 'prefix') in the backing store (such as the durable baggage), and preserved in future incarnations.

A detached().mapStore, on the other hand, does not reserve the label, nor populate it automatically, so it is essentially anonymous. So, to preserve it, you need to connect it to the backing store some other way, like putting it in another store or in an exo object's state.

detached() was created to avoid having to manage a dynamic set of reserved labels, leaving the organization to the programmer instead of the default guard rails that zones (and their underlying makeOnce) give you.