Chuck Norris! (or: Added code for chapter 9)

chapter_9/chucky/README.md

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+# Chucky - A Distributed and Fault-Tolerant Chuck Norris Facts Disher
+
+![Chuck](http://i.imgur.com/wwFsWiA.jpg)
+
+## Step 1: Figure out your hostname
+
+```
+% hostname -s
+imac
+```
+
+## Step 2: Configure `config/NODE_NAME.config`
+
+Here's an example:
+
+```elixir
+[{kernel,
+  [{distributed, 
+    [{chucky,
+      5000,
+      ['a@imac', {'b@imac', 'c@imac'}]}]},
+   {sync_nodes_mandatory, ['b@imac', 'c@imac']},
+   {sync_nodes_timeout, 30000}
+  ]}].
+```
+
+## Step 3: Compile
+
+
+```
+% mix compile
+```
+
+## Step 4: Run it!
+
+Open 3 different terminals, and on each of them, run these commands:
+
+```
+% iex --sname a -pa _build/dev/lib/chucky/ebin --app chucky --erl "-config config/a.config"
+
+% iex --sname b -pa _build/dev/lib/chucky/ebin --app chucky --erl "-config config/b.config"
+
+% iex --sname c -pa _build/dev/lib/chucky/ebin --app chucky --erl "-config config/c.config"
+```
+
+In each terminal, run:
+
+```elixir
+iex > Chucky.fact
+"In a fight between Batman and Darth Vader, the winner would be Chuck Norris."
+```
+
+You can also use `Application.started_applications/1` to see where the application is being run on.
+
+## Step 5: Watching failover in action
+
+Kill the first session (`a@HOSTNAME`), then watch `b@HOSTNAME` get started:
+
+```
+07:33:04.831 [info]  b@manticore starting distributed
+
+07:33:12.025 [info]  Application chucky exited: :stopped
+
+07:33:42.300 [info]  b@manticore starting distributed
+```
+
+## Step 6: Watching takeover in action
+
+Start `a@HOSTNAME` again:
+
+```
+% iex --sname a -pa _build/dev/lib/chucky/ebin --app chucky --erl "-config config/a.config"
+```
+
+Watch `a@HOSTNAME` take over `b@HOSTNAME`:
+
+```
+07:39:49.820 [info]  a@manticore is taking over b@manticore
+```
+

chapter_9/chucky/config/a.config

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+[{kernel,
+  [{distributed, 
+    [{chucky,
+      5000,
+      [a@manticore, {b@manticore, c@manticore}]}]},
+   {sync_nodes_mandatory, [b@manticore, c@manticore]},
+   {sync_nodes_timeout, 30000}
+  ]}].

chapter_9/chucky/config/b.config

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+[{kernel,
+  [{distributed, 
+    [{chucky,
+      5000,
+      [a@manticore, {b@manticore, c@manticore}]}]},
+   {sync_nodes_mandatory, [a@manticore, c@manticore]},
+   {sync_nodes_timeout, 30000}
+  ]}].

chapter_9/chucky/config/c.config

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+[{kernel, 
+  [{distributed, 
+    [{chucky,
+      5000,
+      [a@manticore, {b@manticore, c@manticore}]}]},
+   {sync_nodes_mandatory, [a@manticore, b@manticore]},
+   {sync_nodes_timeout, 30000} 
+  ]}].

chapter_9/chucky/config/config.exs

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+# This file is responsible for configuring your application
+# and its dependencies with the aid of the Mix.Config module.
+use Mix.Config
+
+# This configuration is loaded before any dependency and is restricted
+# to this project. If another project depends on this project, this
+# file won't be loaded nor affect the parent project. For this reason,
+# if you want to provide default values for your application for
+# 3rd-party users, it should be done in your "mix.exs" file.
+
+# You can configure for your application as:
+#
+#     config :chucky, key: :value
+#
+# And access this configuration in your application as:
+#
+#     Application.get_env(:chucky, :key)
+#
+# Or configure a 3rd-party app:
+#
+#     config :logger, level: :info
+#
+
+# It is also possible to import configuration files, relative to this
+# directory. For example, you can emulate configuration per environment
+# by uncommenting the line below and defining dev.exs, test.exs and such.
+# Configuration from the imported file will override the ones defined
+# here (which is why it is important to import them last).
+#
+#     import_config "#{Mix.env}.exs"

chapter_9/chucky/lib/chucky.ex

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+defmodule Chucky do
+  use Application
+  require Logger
+
+  def start(type, _args) do
+    import Supervisor.Spec
+    children = [
+      worker(Chucky.Server, [])
+    ]
+
+  case type do
+    :normal ->
+      Logger.info("Application is started on #{node}")
+
+    {:takeover, old_node} ->
+      Logger.info("#{node} is taking over #{old_node}")
+
+    {:failover, old_node} ->
+      Logger.info("#{old_node} is failing over to #{node}")
+  end
+
+  opts = [strategy: :one_for_one, name: {:global, Chucky.Supervisor}]
+  Supervisor.start_link(children, opts)
+  end
+
+  def fact do
+    Chucky.Server.fact
+  end
+
+end

chapter_9/chucky/lib/server.ex

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+defmodule Chucky.Server do
+  use GenServer
+
+  #######
+  # API #
+  #######
+
+  def start_link do
+    GenServer.start_link(__MODULE__, [], [name: {:global, __MODULE__}])
+  end
+
+  def fact do
+    GenServer.call({:global, __MODULE__}, :fact)
+  end
+
+  #############
+  # Callbacks #
+  #############
+
+  def init([]) do
+    :random.seed(:os.timestamp)
+    facts = "facts.txt"
+             |> File.read!
+             |> String.split("\n")
+
+    {:ok, facts}
+  end
+
+  def handle_call(:fact, _from, facts) do
+    random_fact = facts 
+                  |> Enum.shuffle 
+                  |> List.first
+
+    {:reply, random_fact, facts}
+  end
+
+end

chapter_9/chucky/mix.exs

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+defmodule Chucky.Mixfile do
+  use Mix.Project
+
+  def project do
+    [app: :chucky,
+     version: "0.0.1",
+     elixir: "~> 1.1",
+     build_embedded: Mix.env == :prod,
+     start_permanent: Mix.env == :prod,
+     deps: deps]
+  end
+
+  def application do
+    [applications: [:logger],
+       # registered: [Chucky, Chucky.Supervisor, Chucky.Server],
+              mod: {Chucky, []}]
+  end
+
+  defp deps do
+    []
+  end
+
+end

chapter_9/chucky/test/chucky_test.exs

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+defmodule ChuckyTest do
+  use ExUnit.Case
+  doctest Chucky
+
+  test "the truth" do
+    assert 1 + 1 == 2
+  end
+end

chapter_9/chucky/test/test_helper.exs

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+ExUnit.start()