Arc.Watch behaviour (cratis_arc v0.1.0)

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A source of change notifications for observable queries.

@observe watch: [...] accepts Chronicle read model modules, and {module, target} pairs where module implements this behaviour. Persistence packages use it to re-run a query when their data changes, for example ArcMongo.watch/1 over a MongoDB change stream.

subscribe/3 runs when the subscription starts, with the context of the caller (so a watcher can follow the caller's tenant), and must arrange for {:arc_notify, target} to be sent to owner whenever the watched data may have changed. Arc debounces bursts and re-runs the query. unsubscribe/1 is called with the returned handle when the subscription ends.

Summary

Callbacks

subscribe(target, ctx, owner)
unsubscribe(handle)

Callbacks

subscribe(target, ctx, owner)

@callback subscribe(target :: term(), ctx :: Arc.Context.t(), owner :: pid()) ::
  {:ok, handle :: term()} | {:error, term()}

unsubscribe(handle)

@callback unsubscribe(handle :: term()) :: :ok