Use a registry for nts clients

lib/chronoscope/application.ex

@@ -15,8 +15,9 @@ defmodule Chronoscope.Application do
       {Finch, name: Chronoscope.Finch},
       # Start a worker by calling: Chronoscope.Worker.start_link(arg)
       # {Chronoscope.Worker, arg},
-      {DynamicSupervisor, name: Chronoscope.DynamicSupervisor, strategy: :one_for_one},
-      {Task.Supervisor, name: Chronoscope.TaskSupervisor},
+      {DynamicSupervisor, name: Chronoscope.NTS.DynamicSupervisor, strategy: :one_for_one},
+      {Task.Supervisor, name: Chronoscope.NTS.TaskSupervisor},
+      {Registry, [keys: :unique, name: Chronoscope.NTS.Registry]},
       # Start to serve requests, typically the last entry
       ChronoscopeWeb.Endpoint
     ]

lib/chronoscope/nts.ex

@@ -14,19 +14,26 @@ defmodule Chronoscope.NTS do
   end
 
   def list() do
-    Chronoscope.DynamicSupervisor
+    NTS.DynamicSupervisor
     |> DynamicSupervisor.which_children()
     |> Enum.map(fn {_, pid, _, _} -> GenServer.call(pid, :list) end)
   end
 
   def key_establishment(host, port) do
-    # todo don't use atoms for this
-    name = String.to_atom("#{host}:#{port}")
+    name = "#{host}:#{port}"
 
-    if GenServer.whereis(name) == nil do
-      DynamicSupervisor.start_child(Chronoscope.DynamicSupervisor, {NTS.Client, host: host, port: port, name: name})
-    end
+    case Registry.lookup(NTS.Registry, name) do
+      [{pid, _}] ->
+        GenServer.call(pid, :key_establishment)
 
-    GenServer.call(name, :key_establishment)
+      [] ->
+        NTS.DynamicSupervisor
+        |> DynamicSupervisor.start_child({
+          NTS.Client,
+          host: host, port: port, name: {:via, Registry, {NTS.Registry, name}}
+        })
+
+        key_establishment(host, port)
+    end
   end
 end

lib/chronoscope/nts/client.ex

@@ -1,6 +1,7 @@
 defmodule Chronoscope.NTS.Client do
   use GenServer
 
+  alias Chronoscope.NTS
   alias Chronoscope.NTS.KeyEstablishmentClient
 
   @interval_in_seconds 30
@@ -54,7 +55,7 @@ defmodule Chronoscope.NTS.Client do
   defp server_response(state) do
     server = Map.take(state, [:host, :port])
 
-    Chronoscope.TaskSupervisor
+    NTS.TaskSupervisor
     |> Task.Supervisor.async(fn -> KeyEstablishmentClient.key_establishment(server) end)
     |> Task.await()
   end