config option update_file now contains updated json of working instances after sync

lib/farside.ex

@@ -92,4 +92,17 @@ defmodule Farside do
         instance
     end
   end
+
+
+  def save_results(file, data) do
+    {:ok, file} = File.open(file, [:append])
+    bin = :erlang.term_to_binary(data)
+    IO.binwrite(file, bin)
+    File.close(file)
+  end
+
+  def restore_term(file) do
+    {:ok,bin} = File.read(file)
+    :erlang.binary_to_term(bin)
+  end
 end

lib/farside/application.ex

@@ -13,7 +13,7 @@ defmodule Farside.Application do
   def start(_type, _args) do
     port =
       case Application.fetch_env!(:farside, :port) do
-        nil -> System.get_env("PORT")
+        nil -> System.get_env("PORT", "4001")
         port -> port
       end
 

lib/farside/instance.ex

@@ -6,7 +6,7 @@ defmodule Farside.Instance do
   alias Farside.Http
 
   @registry_name :servers
-  @update_file Application.fetch_env!(:farside, :update_file)
+  @update_file Application.fetch_env!(:farside, :update_file) <> ".json"
 
   def child_spec(args) do
     %{
@@ -69,7 +69,9 @@ defmodule Farside.Instance do
 
     :ets.insert(state.ref, {:data, service})
 
-    File.write(@update_file, service.fallback)
+    encoded = service |> Map.from_struct() |> Jason.encode!()
+
+    Farside.save_results(@update_file, encoded)
 
     {:noreply, state}
   end

lib/farside/instances.ex

@@ -3,15 +3,13 @@ defmodule Farside.Instances do
 
   def sync() do
     update_file = Application.fetch_env!(:farside, :update_file)
+    update_json = update_file <> ".json"
 
-    File.rm("#{update_file}-prev")
+    File.rename(update_json, "#{update_file}-#{to_string(DateTime.utc_now()) <> ".json"}")
 
-    File.rename(update_file, "#{update_file}-prev")
-
-    File.write(update_file, "")
+    File.write(update_json, "")
 
     LastUpdated.value(DateTime.utc_now())
-
     Farside.Instance.Supervisor.update_children()
   end
 end