Token resolver now a GenServer with client methods that directly hit ETS

Author: hiett

lib/srh.ex

@@ -3,6 +3,7 @@ defmodule Srh do
 
   def start(_type, _args) do
     children = [
+      Srh.Auth.TokenResolver,
       {GenRegistry, worker_module: Srh.Redis.Client},
       {
         Plug.Cowboy,

lib/srh/auth/token_resolver.ex

@@ -1,30 +1,78 @@
 defmodule Srh.Auth.TokenResolver do
+  use GenServer
+
   @mode Application.fetch_env!(:srh, :mode)
   @file_path Application.fetch_env!(:srh, :file_path)
   @file_hard_reload Application.fetch_env!(:srh, :file_hard_reload)
 
-  @config_file_data nil
+  @ets_table_name :srh_token_resolver
+
+  def start_link() do
+    GenServer.start_link(__MODULE__, {}, [])
+  end
+
+  def child_spec(_opts) do
+    %{
+      id: :token_resolver,
+      start: {__MODULE__, :start_link, []},
+      type: :supervisor
+    }
+  end
+
+  def init(_arg) do
+    IO.puts("Token resolver started")
+
+    # Create the ETS table
+    table = :ets.new(@ets_table_name, [:named_table, read_concurrency: true])
+
+    # Populate the ETS table with data from storage
+    do_init_load(@mode)
+
+    {
+      :ok,
+      %{
+        table: table
+      }
+    }
+  end
 
   def resolve(token) do
     IO.puts("Resolving token: #{token}")
 
     do_resolve(@mode, token)
   end
 
-  defp do_resolve("file", token) do
-    #    if @config_file_data == nil || @file_hard_reload do
-    #      @config_file_data = Jason.decode!(File.read!(@file_path))
-    #      IO.puts("Reloaded config file from disk. #{Jason.encode!(@config_file_data)}")
-    #    end
+  # Server methods
+  def handle_call(_msg, _from, state) do
+    {:reply, :ok, state}
+  end
+
+  def handle_cast(_msg, state) do
+    {:noreply, state}
+  end
 
+  # Internal server
+  defp do_init_load("file") do
     config_file_data = Jason.decode!(File.read!(@file_path))
-    IO.puts("Reloaded config file from disk. #{Jason.encode!(config_file_data)}")
+    IO.puts("Loaded config file from disk. #{map_size(config_file_data)} entries.")
+    # Load this into ETS
+    Enum.each(
+      config_file_data,
+      &(:ets.insert(@ets_table_name, &1))
+    )
+  end
+
+  defp do_init_load(_), do: :ok
+
+  # Internal, but client side, methods. These are client side to prevent GenServer lockup
+  defp do_resolve("file", token) do
+    #    if @hard_file_reload do
+    #      do_init_load("file")
+    #    end
 
-    case Map.get(config_file_data, token) do
-      nil ->
-        {:error, "Invalid token"}
-      connection_info ->
-        {:ok, connection_info}
+    case :ets.lookup(@ets_table_name, token) do
+      [{^token, connection_info}] -> {:ok, connection_info}
+      [] -> {:error, "Invalid token"}
     end
   end