From a84d2270409cddb218875a2e010cea94f54574f5 Mon Sep 17 00:00:00 2001
From: Jordan Bracco <href@random.sh>
Date: Wed, 13 May 2020 11:44:25 +0200
Subject: [PATCH] NimblePool implementation WIP

---
 README.md                    | 13 ++++++++-
 lib/gen_magic/pool.ex        | 55 ++++++++++++++++++++++++++++++++++++
 mix.exs                      |  3 +-
 mix.lock                     |  1 +
 test/gen_magic/pool_test.exs |  9 ++++++
 5 files changed, 79 insertions(+), 2 deletions(-)
 create mode 100644 lib/gen_magic/pool.ex
 create mode 100644 test/gen_magic/pool_test.exs

diff --git a/README.md b/README.md
index d89e486..30bab53 100644
--- a/README.md
+++ b/README.md
@@ -78,7 +78,7 @@ iex(1)> GenMagic.Helpers.perform_once(Path.join(File.cwd!(), "Makefile"))
 
 ### Supervised Requests
 
-The Server should be run under a pool which provides concurrency *and* resiliency.
+The Server should be run under a supervisor which provides resiliency.
 
 Here we run it under a supervisor:
 
@@ -96,6 +96,17 @@ iex(2)> GenMagic.Server.perform(:gen_magic, Path.expand("~/.bash_history"))
 
 Note that in this case we have opted to use a named process.
 
+### Pool
+
+For concurrency *and* resiliency, you may start the `GenMagic.Pool`. By default, it will start a `GenMagic.Server`
+worker per online scheduler:
+
+```elixir
+iex(1)> GenMagic.Pool.start_link([])
+iex(2)> GenMagic.Pool.perform(GenMagic.Pool, Path.expand("~/.bash_history"))
+{:ok, [mime_type: "text/plain", encoding: "us-ascii", content: "ASCII text"]}
+```
+
 ### Check Uploaded Files
 
 If you use Phoenix, you can inspect the file from your controller:
diff --git a/lib/gen_magic/pool.ex b/lib/gen_magic/pool.ex
new file mode 100644
index 0000000..fac4cd6
--- /dev/null
+++ b/lib/gen_magic/pool.ex
@@ -0,0 +1,55 @@
+defmodule GenMagic.Pool do
+  @behaviour NimblePool
+
+  def start_link(options, pool_size \\ nil) do
+    pool_size = pool_size || System.schedulers_online()
+    NimblePool.start_link(worker: {__MODULE__, options}, pool_size: pool_size)
+  end
+
+  def perform(pool, path, opts \\ []) do
+    pool_timeout = Keyword.get(opts, :pool_timeout, 5000)
+    timeout = Keyword.get(opts, :timeout, 5000)
+
+    NimblePool.checkout!(pool, :checkout, fn _from, server ->
+      {GenMagic.perform(server, path, timeout), server}
+    end, pool_timeout)
+  end
+
+  @impl NimblePool
+  def init_pool(options) do
+    {name, options} = case Keyword.pop(options, :name) do
+      {name, options} when is_atom(name) -> {name, options}
+      {nil, options} -> {__MODULE__, options}
+      {_, options} -> {nil, options}
+    end
+    if name, do: Process.register(self(), atom)
+    {:ok, options}
+  end
+
+  @impl NimblePool
+  def init_worker(options) do
+    {:ok, server} = GenMagic.Server.start_link(options)
+    {:ok, server, nil}
+  end
+
+  @impl NimblePool
+  def handle_checkout(:checkout, _, server, state) do
+    {:ok, server, server, pool_state}
+  end
+
+  @impl NimblePool
+  def handle_checkin(server, _from, _old_server, state) do
+    {:ok, server, state}
+  end
+
+  @impl NimblePool
+  def terminate_worker(_reason, _worker, state) do
+    {:ok, state}
+  end
+
+  @impl NimblePool
+  def terminate(_reason, _conn, state) do
+    {:ok, state}
+  end
+
+end
diff --git a/mix.exs b/mix.exs
index 11ebdaf..83c1597 100644
--- a/mix.exs
+++ b/mix.exs
@@ -44,7 +44,8 @@ defmodule GenMagic.MixProject do
       {:credo, "~> 1.4.0", only: [:dev, :test], runtime: false},
       {:dialyxir, "~> 1.0.0-rc.6", only: :dev, runtime: false},
       {:ex_doc, ">= 0.0.0", only: :dev, runtime: false},
-      {:elixir_make, "~> 0.4", runtime: false}
+      {:elixir_make, "~> 0.4", runtime: false},
+      {:nimble_pool, "~> 0.1"}
     ]
   end
 
diff --git a/mix.lock b/mix.lock
index 3ebe0c6..3317183 100644
--- a/mix.lock
+++ b/mix.lock
@@ -12,4 +12,5 @@
   "makeup": {:hex, :makeup, "1.0.1", "82f332e461dc6c79dbd82fbe2a9c10d48ed07146f0a478286e590c83c52010b5", [:mix], [{:nimble_parsec, "~> 0.5.0", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "49736fe5b66a08d8575bf5321d716bac5da20c8e6b97714fec2bcd6febcfa1f8"},
   "makeup_elixir": {:hex, :makeup_elixir, "0.14.0", "cf8b7c66ad1cff4c14679698d532f0b5d45a3968ffbcbfd590339cb57742f1ae", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "d4b316c7222a85bbaa2fd7c6e90e37e953257ad196dc229505137c5e505e9eff"},
   "nimble_parsec": {:hex, :nimble_parsec, "0.5.3", "def21c10a9ed70ce22754fdeea0810dafd53c2db3219a0cd54cf5526377af1c6", [:mix], [], "hexpm", "589b5af56f4afca65217a1f3eb3fee7e79b09c40c742fddc1c312b3ac0b3399f"},
+  "nimble_pool": {:hex, :nimble_pool, "0.1.0", "ffa9d5be27eee2b00b0c634eb649aa27f97b39186fec3c493716c2a33e784ec6", [:mix], [], "hexpm", "343a1eaa620ddcf3430a83f39f2af499fe2370390d4f785cd475b4df5acaf3f9"},
 }
diff --git a/test/gen_magic/pool_test.exs b/test/gen_magic/pool_test.exs
new file mode 100644
index 0000000..f336e12
--- /dev/null
+++ b/test/gen_magic/pool_test.exs
@@ -0,0 +1,9 @@
+defmodule GenMagic.PoollTest do
+  use GenMagic.MagicCase
+
+  test "pool" do
+    {:ok, _} = GenMagic.Pool.start_link([name: TestPool])
+    assert {:ok, _} = GenMagic.Pool.perform(TestPool, absolute_path("Makefile"))
+  end
+
+end