Read Models

Read models are shared Chronicle concepts. Querying, snapshots, watching, and consistency are documented in the shared Chronicle section.

• Read models
• Getting a single read model
• Getting read model collections
• Elixir client setup

Watching for live changes

Chronicle.ReadModels.watch/2 subscribes the calling process to live changesets for a read model over the kernel’s server-streaming Watch RPC. Elixir has no IObservable/ async-iterable equivalent to the C# and TypeScript clients’ Watch<TReadModel>(), so this follows the same message-based idiom as Chronicle.Connections.Lifecycle.subscribe/1.

{:ok, watcher} = Chronicle.ReadModels.watch(MyApp.ReadModels.AccountInfo)

receive do
  {:chronicle_read_model_changed, MyApp.ReadModels.AccountInfo, changeset} ->
    # changeset is a %Chronicle.ReadModels.Changeset{} with :model_key, :read_model,
    # :change_type (:added | :modified | :removed), :event_sequence_number, and more.
    IO.inspect(changeset.read_model)

  {:chronicle_read_model_watch_error, MyApp.ReadModels.AccountInfo, reason} ->
    # The stream failed and the watch has ended — call watch/2 again to resume.
    IO.inspect(reason)
end

Chronicle.ReadModels.unwatch(watcher)

Dehydrating a session

A read-model session (created implicitly whenever you read with a :session_id) normally expires on its own. dehydrate_session/4 explicitly cleans one up once the caller is done with it, releasing the resources Chronicle held for it right away.

:ok =
  Chronicle.ReadModels.dehydrate_session(
    MyApp.ReadModels.AccountInfo,
    account_id,
    session_id
  )