From 9bae951c555f9c25876968fa98853253b7007a0f Mon Sep 17 00:00:00 2001
From: kballou <kballou@devnulllabs.io>
Date: Fri, 24 Nov 2017 10:16:06 -0700
Subject: Level up the Echo Server

This should enable the upgrade process to retain connections

- Replace our simple task supervisor with a custom `simple_one_for_one`
  supervisor

- Upgrade the echo server to use a `GenServer` behaviour
---
 lib/octonetcat/accepter.ex          |  6 +-----
 lib/octonetcat/server_supervisor.ex | 23 +++++++++++++++++++++++
 lib/octonetcat/servers/echo.ex      | 28 ++++++++++++++++------------
 lib/octonetcat/supervisor.ex        |  2 +-
 mix.exs                             |  2 +-
 5 files changed, 42 insertions(+), 19 deletions(-)
 create mode 100644 lib/octonetcat/server_supervisor.ex

diff --git a/lib/octonetcat/accepter.ex b/lib/octonetcat/accepter.ex
index a398676..9a570c1 100644
--- a/lib/octonetcat/accepter.ex
+++ b/lib/octonetcat/accepter.ex
@@ -18,11 +18,7 @@ defmodule Octonetcat.Accepter do
     {:ok, client} = :gen_tcp.accept(socket)
     Logger.info("Accepted connection")
     Logger.info("Passing to Echo Server")
-    {:ok, pid} = Task.Supervisor.start_child(
-      Octonetcat.TaskSupervisor,
-      Octonetcat.Echo,
-      :serve,
-      [client])
+    {:ok, pid} = Octonetcat.ServerSupervisor.start_server(client)
     :ok = :gen_tcp.controlling_process(client, pid)
     loop_accepter(socket)
   end
diff --git a/lib/octonetcat/server_supervisor.ex b/lib/octonetcat/server_supervisor.ex
new file mode 100644
index 0000000..7aa8e37
--- /dev/null
+++ b/lib/octonetcat/server_supervisor.ex
@@ -0,0 +1,23 @@
+defmodule Octonetcat.ServerSupervisor do
+  @moduledoc """
+  Simple One-for-One Supervisor for Socket servers
+  """
+
+  use Supervisor
+
+  def start_link do
+    Supervisor.start_link(__MODULE__, :ok, name: __MODULE__)
+  end
+
+  def init(:ok) do
+    children = [
+      worker(Octonetcat.Echo, [], restart: :temporary)
+    ]
+
+    supervise(children, strategy: :simple_one_for_one)
+  end
+
+  def start_server(socket) do
+    Supervisor.start_child(__MODULE__, [socket])
+  end
+end
diff --git a/lib/octonetcat/servers/echo.ex b/lib/octonetcat/servers/echo.ex
index e416d9d..8ad6aff 100644
--- a/lib/octonetcat/servers/echo.ex
+++ b/lib/octonetcat/servers/echo.ex
@@ -6,23 +6,27 @@ defmodule Octonetcat.Echo do
   dies on failure or disconnect.
   """
 
+  use GenServer
   require Logger
 
-  def serve(socket) do
-    socket
-    |> read_line()
-    |> write_line!(socket)
+  def start_link(socket) do
+    GenServer.start_link(__MODULE__, socket)
+  end
 
-    serve(socket)
+  def init(socket) do
+    :ok = :inet.setopts(socket, active: true)
+    {:ok, %{socket: socket}}
+  end
+
+  def handle_info({:tcp, _, msg}, state = %{socket: socket}) do
+    msg
+    |> write_line!(socket)
+    {:noreply, state}
   end
 
-  def read_line(socket) do
-    case :gen_tcp.recv(socket, 0) do
-      {:ok, line} -> line
-      {:error, reason} ->
-        Logger.error(reason)
-        Process.exit(self(), :normal)
-    end
+  def handle_info({:tcp_closed, _}, _state) do
+    Logger.info("#{__MODULE__}: Connection closing...")
+    {:stop, :normal, %{}}
   end
 
   def write_line!(line, socket) do
diff --git a/lib/octonetcat/supervisor.ex b/lib/octonetcat/supervisor.ex
index 50a5f66..64bc27c 100644
--- a/lib/octonetcat/supervisor.ex
+++ b/lib/octonetcat/supervisor.ex
@@ -11,7 +11,7 @@ defmodule Octonetcat.Supervisor do
 
   def init(_) do
     children = [
-      supervisor(Task.Supervisor, [[name: Octonetcat.TaskSupervisor]]),
+      supervisor(Octonetcat.ServerSupervisor, []),
       worker(Task, [Octonetcat.Accepter, :accept, []])
     ]
 
diff --git a/mix.exs b/mix.exs
index e96830b..954f1ec 100644
--- a/mix.exs
+++ b/mix.exs
@@ -6,7 +6,7 @@ defmodule Octonetcat.Mixfile do
       app: :octonetcat,
       description: "Demo Echo Server Application",
       package: package(),
-      version: "0.2.1",
+      version: "0.3.0",
       elixir: "~> 1.5",
       start_permanent: Mix.env == :prod,
       docs: docs(),
-- 
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