Code for step 8

lib/book_store/application.ex

@@ -17,6 +17,8 @@ defmodule BookStore.Application do
       BookStore.BookRegistry.child_spec(),
       # Start the Book DynamicSupervisor
       BookStore.BookDynamicSupervisor,
+      # Hydrate process state
+      BookStore.BookStateHydrator,
       # Start the Endpoint (http/https)
       BookStoreWeb.Endpoint
       # Start a worker by calling: BookStore.Worker.start_link(arg)

lib/book_store/book_state_hydrator.ex

@@ -0,0 +1,26 @@
+defmodule BookStore.BookStateHydrator do
+  use GenServer, restart: :transient
+
+  require Logger
+
+  alias BookStore.Books.Book
+  alias BookStore.BookDynamicSupervisor
+
+  def start_link(state) do
+    GenServer.start_link(__MODULE__, state, name: __MODULE__, timeout: 10_000)
+  end
+
+  @impl true
+  def init(_) do
+    Logger.info("#{inspect(Time.utc_now())} Starting Books process hydration")
+
+    BookStore.Books.all()
+    |> Enum.each(fn %Book{} = book ->
+      BookDynamicSupervisor.add_book_to_supervisor(book)
+    end)
+
+    Logger.info("#{inspect(Time.utc_now())} Completed Books process hydration")
+
+    :ignore
+  end
+end