Cluster Gigalixir Apps Using Custom Libcluster Strategy

.gitignore

@@ -9,6 +9,7 @@ erl_crash.dump
 
 # Static artifacts
 /node_modules
+/assets/node_modules
 
 # Since we are building assets from web/static,
 # we ignore priv/static. You may want to comment

config/prod.exs

@@ -73,6 +73,12 @@ config :gigalixir_getting_started, GigalixirGettingStarted.Repo,
 
 config :libcluster,
   topologies: [
+    gigalixir_example: [
+      strategy: GigalixirGettingStarted.Libcluster.Strategy,
+      config: [
+        url: "https://bar.gigalixirapp.com/nodes"
+      ]
+    ],
     k8s_example: [
       strategy: Cluster.Strategy.Kubernetes,
       config: [

lib/gigalixir_getting_started/libcluster/strategy.ex

@@ -0,0 +1,64 @@
+defmodule GigalixirGettingStarted.Libcluster.Strategy do
+  use GenServer
+  use Cluster.Strategy
+  import Cluster.Logger
+
+  alias Cluster.Strategy.State
+
+  @default_polling_interval 5_000
+
+  def start_link(opts), do: GenServer.start_link(__MODULE__, opts)
+  def init(opts) do
+    state = %State{
+      topology: Keyword.fetch!(opts, :topology),
+      connect: Keyword.fetch!(opts, :connect),
+      disconnect: Keyword.fetch!(opts, :disconnect),
+      config: Keyword.fetch!(opts, :config),
+      meta: MapSet.new([])
+    }
+    {:ok, state, 0}
+  end
+
+  def handle_info(:timeout, state) do
+    handle_info(:load, state)
+  end
+  def handle_info(:load, %State{topology: topology, connect: connect, disconnect: disconnect} = state) do
+    new_nodelist = MapSet.new(get_nodes(state))
+    added        = MapSet.difference(new_nodelist, state.meta)
+    removed      = MapSet.difference(state.meta, new_nodelist)
+    new_nodelist = case Cluster.Strategy.disconnect_nodes(topology, disconnect, MapSet.to_list(removed)) do
+                :ok ->
+                  new_nodelist
+                {:error, bad_nodes} ->
+                  # Add back the nodes which should have been removed, but which couldn't be for some reason
+                  Enum.reduce(bad_nodes, new_nodelist, fn {n, _}, acc ->
+                    MapSet.put(acc, n)
+                  end)
+              end
+    new_nodelist = case Cluster.Strategy.connect_nodes(topology, connect, MapSet.to_list(added)) do
+              :ok ->
+                new_nodelist
+              {:error, bad_nodes} ->
+                # Remove the nodes which should have been added, but couldn't be for some reason
+                Enum.reduce(bad_nodes, new_nodelist, fn {n, _}, acc ->
+                  MapSet.delete(acc, n)
+                end)
+            end
+    Process.send_after(self(), :load, Keyword.get(state.config, :polling_interval, @default_polling_interval))
+    {:noreply, %{state | :meta => new_nodelist}}
+  end
+  def handle_info(_, state) do
+    {:noreply, state}
+  end
+
+  @spec get_nodes(State.t) :: [atom()]
+  defp get_nodes(%State{topology: topology, config: config}) do
+    config
+    |> Keyword.get(:url)
+    |> HTTPoison.get!
+    |> Map.get(:body)
+    |> Poison.decode!
+    |> Map.get("data")
+    |> Enum.map(&String.to_atom/1)
+  end
+end

mix.exs

@@ -19,7 +19,7 @@ defmodule GigalixirGettingStarted.Mixfile do
   def application do
     [mod: {GigalixirGettingStarted, []},
      applications: [:phoenix, :phoenix_pubsub, :phoenix_html, :cowboy, :logger, :gettext,
-                    :phoenix_ecto, :postgrex, :libcluster, :ssl, :runtime_tools]]
+                    :phoenix_ecto, :postgrex, :libcluster, :ssl, :runtime_tools, :httpoison]]
   end
 
   # Specifies which paths to compile per environment.
@@ -36,6 +36,7 @@ defmodule GigalixirGettingStarted.Mixfile do
      {:postgrex, ">= 0.13.3"},
      {:phoenix_html, "~> 2.6"},
      {:phoenix_live_reload, "~> 1.0", only: :dev},
+     {:httpoison, "~> 0.13"},
      {:gettext, "~> 0.11"},
      {:cowboy, "~> 1.0"},
      {:libcluster, "~> 2.0.3"},

mix.lock

@@ -1,4 +1,5 @@
-%{"connection": {:hex, :connection, "1.0.4", "a1cae72211f0eef17705aaededacac3eb30e6625b04a6117c1b2db6ace7d5976", [:mix], []},
+%{"certifi": {:hex, :certifi, "2.0.0", "a0c0e475107135f76b8c1d5bc7efb33cd3815cb3cf3dea7aefdd174dabead064", [], [], "hexpm"},
+  "connection": {:hex, :connection, "1.0.4", "a1cae72211f0eef17705aaededacac3eb30e6625b04a6117c1b2db6ace7d5976", [:mix], []},
   "cowboy": {:hex, :cowboy, "1.0.4", "a324a8df9f2316c833a470d918aaf73ae894278b8aa6226ce7a9bf699388f878", [:make, :rebar], [{:cowlib, "~> 1.0.0", [hex: :cowlib, optional: false]}, {:ranch, "~> 1.0", [hex: :ranch, optional: false]}]},
   "cowlib": {:hex, :cowlib, "1.0.2", "9d769a1d062c9c3ac753096f868ca121e2730b9a377de23dec0f7e08b1df84ee", [:make], []},
   "db_connection": {:hex, :db_connection, "1.1.2", "2865c2a4bae0714e2213a0ce60a1b12d76a6efba0c51fbda59c9ab8d1accc7a8", [], [{:connection, "~> 1.0.2", [hex: :connection, repo: "hexpm", optional: false]}, {:poolboy, "~> 1.5", [hex: :poolboy, repo: "hexpm", optional: true]}, {:sbroker, "~> 1.0", [hex: :sbroker, repo: "hexpm", optional: true]}], "hexpm"},
@@ -7,8 +8,13 @@
   "ecto": {:hex, :ecto, "2.1.2", "8d7bde4170b33e1049850a5dbe0112bfd232824e63c73ee63383df4c6ffd4064", [:mix], [{:db_connection, "~> 1.1", [hex: :db_connection, optional: true]}, {:decimal, "~> 1.2", [hex: :decimal, optional: false]}, {:mariaex, "~> 0.8.0", [hex: :mariaex, optional: true]}, {:poison, "~> 2.2 or ~> 3.0", [hex: :poison, optional: true]}, {:poolboy, "~> 1.5", [hex: :poolboy, optional: false]}, {:postgrex, "~> 0.13.0", [hex: :postgrex, optional: true]}, {:sbroker, "~> 1.0", [hex: :sbroker, optional: true]}]},
   "fs": {:hex, :fs, "0.9.2", "ed17036c26c3f70ac49781ed9220a50c36775c6ca2cf8182d123b6566e49ec59", [:rebar], []},
   "gettext": {:hex, :gettext, "0.13.0", "daafbddc5cda12738bb93b01d84105fe75b916a302f1c50ab9fb066b95ec9db4", [:mix], []},
+  "hackney": {:hex, :hackney, "1.9.0", "51c506afc0a365868469dcfc79a9d0b94d896ec741cfd5bd338f49a5ec515bfe", [], [{:certifi, "2.0.0", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "5.1.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "1.0.1", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "1.0.2", [hex: :mimerl, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "1.1.1", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}], "hexpm"},
+  "httpoison": {:hex, :httpoison, "0.13.0", "bfaf44d9f133a6599886720f3937a7699466d23bb0cd7a88b6ba011f53c6f562", [], [{:hackney, "~> 1.8", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm"},
+  "idna": {:hex, :idna, "5.1.0", "d72b4effeb324ad5da3cab1767cb16b17939004e789d8c0ad5b70f3cea20c89a", [], [{:unicode_util_compat, "0.3.1", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm"},
   "libcluster": {:hex, :libcluster, "2.0.3", "be2b31161f14ff95c092431acfa5259d8e5d98be31dab634591f0033caca0848", [:mix], [{:poison, "~> 2.2", [hex: :poison, optional: false]}]},
+  "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [], [], "hexpm"},
   "mime": {:hex, :mime, "1.0.1", "05c393850524767d13a53627df71beeebb016205eb43bfbd92d14d24ec7a1b51", [:mix], []},
+  "mimerl": {:hex, :mimerl, "1.0.2", "993f9b0e084083405ed8252b99460c4f0563e41729ab42d9074fd5e52439be88", [], [], "hexpm"},
   "phoenix": {:hex, :phoenix, "1.2.1", "6dc592249ab73c67575769765b66ad164ad25d83defa3492dc6ae269bd2a68ab", [:mix], [{:cowboy, "~> 1.0", [hex: :cowboy, optional: true]}, {:phoenix_pubsub, "~> 1.0", [hex: :phoenix_pubsub, optional: false]}, {:plug, "~> 1.1", [hex: :plug, optional: false]}, {:poison, "~> 1.5 or ~> 2.0", [hex: :poison, optional: false]}]},
   "phoenix_ecto": {:hex, :phoenix_ecto, "3.2.1", "6cf11d590c61977f50fcb98ad8a10ee90ba8670a82cbf5eaf49cfaee2e95e8b7", [:mix], [{:ecto, "~> 2.1", [hex: :ecto, optional: false]}, {:phoenix_html, "~> 2.9", [hex: :phoenix_html, optional: false]}, {:plug, "~> 1.0", [hex: :plug, optional: false]}]},
   "phoenix_html": {:hex, :phoenix_html, "2.9.2", "371160b30cf4e10443b015efce6f03e1f19aae98ff6487620477b13a5b2ef660", [:mix], [{:plug, "~> 1.0", [hex: :plug, optional: false]}]},
@@ -18,4 +24,6 @@
   "poison": {:hex, :poison, "2.2.0", "4763b69a8a77bd77d26f477d196428b741261a761257ff1cf92753a0d4d24a63", [:mix], []},
   "poolboy": {:hex, :poolboy, "1.5.1", "6b46163901cfd0a1b43d692657ed9d7e599853b3b21b95ae5ae0a777cf9b6ca8", [:rebar], []},
   "postgrex": {:hex, :postgrex, "0.13.3", "c277cfb2a9c5034d445a722494c13359e361d344ef6f25d604c2353185682bfc", [], [{:connection, "~> 1.0", [hex: :connection, repo: "hexpm", optional: false]}, {:db_connection, "~> 1.1", [hex: :db_connection, repo: "hexpm", optional: false]}, {:decimal, "~> 1.0", [hex: :decimal, repo: "hexpm", optional: false]}], "hexpm"},
-  "ranch": {:hex, :ranch, "1.2.1", "a6fb992c10f2187b46ffd17ce398ddf8a54f691b81768f9ef5f461ea7e28c762", [:make], []}}
+  "ranch": {:hex, :ranch, "1.2.1", "a6fb992c10f2187b46ffd17ce398ddf8a54f691b81768f9ef5f461ea7e28c762", [:make], []},
+  "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.1", "28a4d65b7f59893bc2c7de786dec1e1555bd742d336043fe644ae956c3497fbe", [], [], "hexpm"},
+  "unicode_util_compat": {:hex, :unicode_util_compat, "0.3.1", "a1f612a7b512638634a603c8f401892afbf99b8ce93a45041f8aaca99cadb85e", [], [], "hexpm"}}

web/controllers/page_controller.ex

@@ -4,4 +4,25 @@ defmodule GigalixirGettingStarted.PageController do
   def index(conn, _params) do
     render conn, "index.html"
   end
+
+  def nodes(conn, params) do
+    json conn, %{
+      data: Node.list ++ [Node.self]
+    }
+  end
+
+  def connect(conn, params) do
+    result = params
+    |> Map.get("url")
+    |> HTTPoison.get!
+    |> Map.get(:body)
+    |> Poison.decode!
+    |> Map.get("data")
+    |> Enum.map(&String.to_atom/1)
+    |> Enum.map(&Node.connect/1)
+
+    json conn, %{
+      data: result
+    }
+  end
 end

web/router.ex

@@ -17,6 +17,8 @@ defmodule GigalixirGettingStarted.Router do
     pipe_through :browser # Use the default browser stack
 
     get "/", PageController, :index
+    get "/nodes", PageController, :nodes
+    get "/connect", PageController, :connect
   end
 
   # Other scopes may use custom stacks.