consistent naming

Author: bigardone

03_global_background_job/lib/background_job/application.ex

@@ -9,12 +9,7 @@ defmodule GlobalBackgroundJob.Application do
   def start(_type, _args) do
     children = [
       {Cluster.Supervisor, [topologies(), [name: GlobalBackgroundJob.ClusterSupervisor]]},
-      {GlobalBackgroundJob.Singleton,
-       [
-         mod: GlobalBackgroundJob.DatabaseCleaner,
-         args: [timeout: :timer.seconds(5)],
-         name: DatabaseCleaner
-       ]}
+      {GlobalBackgroundJob.DatabaseCleaner.Starter, [timeout: :timer.seconds(2)]}
     ]
 
     opts = [strategy: :one_for_one, name: GlobalBackgroundJob.Supervisor]

03_global_background_job/lib/background_job/database_cleaner/starter.ex

@@ -0,0 +1,53 @@
+defmodule GlobalBackgroundJob.DatabaseCleaner.Starter do
+  @moduledoc """
+  GenServer which starts and monitors another process, restarting
+  it when it goes down.
+  """
+
+  use GenServer
+  require Logger
+
+  alias GlobalBackgroundJob.DatabaseCleaner
+
+  def start_link(opts) do
+    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
+  end
+
+  @impl GenServer
+  def init(opts) do
+    pid = start_and_monitor(opts)
+
+    {:ok, {pid, opts}}
+  end
+
+  @impl GenServer
+  def handle_info({:DOWN, _, :process, pid, _reason}, {pid, opts} = state) do
+    log("process down, restarting... #{inspect(state)}")
+
+    {:noreply, {start_and_monitor(opts), opts}}
+  end
+
+  defp start_and_monitor(opts) do
+    log("restarting #{inspect(opts)}...")
+
+    pid =
+      case GenServer.start_link(DatabaseCleaner, opts, name: {:global, DatabaseCleaner}) do
+        {:ok, pid} ->
+          pid
+
+        {:error, {:already_started, pid}} ->
+          log("...already started!")
+          pid
+      end
+
+    Process.monitor(pid)
+
+    log("monitoring #{inspect(pid)}...")
+
+    pid
+  end
+
+  defp log(text) do
+    Logger.info("----[#{node()}] #{__MODULE__} #{text}")
+  end
+end