fix: Change example approach to use Docker Compose

Dockerfile

@@ -0,0 +1,17 @@
+FROM elixir as builder
+
+RUN apt-get update -y \
+  && apt-get install -y build-essential git \
+  && apt-get clean
+
+ENV MIX_ENV=prod
+
+RUN mix local.hex --force && mix local.rebar --force
+ADD ../../ /app
+
+WORKDIR /app
+RUN mix compile
+
+WORKDIR /app/example
+RUN mix release
+CMD [ "_build/prod/rel/example/bin/example", "start", "--sname", "service", "--no-halt" ]

README.md

@@ -2,8 +2,28 @@
 
 Postgres Strategy for [libcluster](https://hexdocs.pm/libcluster/) which is used by Supabase on the [realtime](https://github.com/supabase/realtime) and [supavisor](https://github.com/supabase/supavisor) projects.
 
-It uses Postgres `LISTEN` and `NOTIFICATION` to send the information from a given node and connects them using libcluster.
+You can test it out by running `docker compose up`
 
+![example.png](example.png)
+
+## Installation
+
+The package can be installed
+by adding `libcluster_postgres` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [{:libcluster_postgres, "~> 0.1"}]
+end
+```
+
+## How it works
+
+We connect to a Postgres instance using Postgrex. With the [Postgrex.Notifications](https://hexdocs.pm/postgrex/Postgrex.Notifications.html) module we will track for `LISTEN` events on the configured channel. We'll also use `NOTIFY` queries to send the node's information.
+
+## How to use it
+
+To use it, set your configuration file with the informations for your database:
 
 ```elixir
 config :libcluster,
@@ -22,17 +42,20 @@ config :libcluster,
     ]
   ]
 ```
-
-To see it in use run the script `./test.sh` in this folder and you will see that both nodes connected as expected and are able to list one another.
-
-
-## Installation
-
-The package can be installed
-by adding `libcluster_postgres` to your list of dependencies in `mix.exs`:
+Then add it to your supervision tree:
 
 ```elixir
-def deps do
-  [{:libcluster_postgres, "~> 0.1"}]
+defmodule MyApp do
+  use Application
+
+  def start(_type, _args) do
+    topologies = Application.get_env(:libcluster, :topologies)
+    children = [
+      # ...
+      {Cluster.Supervisor, [topologies]}
+      # ...
+    ]
+    Supervisor.start_link(children, strategy: :one_for_one)
+  end
 end
-```
+```

docker-compose.yml

@@ -1,10 +1,22 @@
 version: "3.8"
 
 services:
-  postgres:
+  db:
     image: postgres:latest
     ports:
       - 5432:5432
     environment:
       POSTGRES_PASSWORD: postgres
       POSTGRES_USER: postgres
+  service1:
+    depends_on:
+      - db
+    build: .
+  service2:
+    depends_on:
+      - db
+    build: .
+  service3:
+    depends_on:
+      - db
+    build: .

example/.formatter.exs

@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

example/.gitignore

@@ -0,0 +1,26 @@
+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+example-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

example/README.md

@@ -0,0 +1,21 @@
+# Example
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `example` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:example, "~> 0.1.0"}
+  ]
+end
+```
+
+Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
+and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
+be found at <https://hexdocs.pm/example>.
+

example/config/config.exs

@@ -0,0 +1,19 @@
+import Config
+
+config :logger, :console,
+  format: "[$level[node:$node] $message\n", metadata: [:node]
+
+config :libcluster, topologies: [
+  postgres: [
+    strategy: Cluster.Strategy.Postgres,
+    config: [
+      hostname: "db",
+      username: "postgres",
+      password: "postgres",
+      database: "postgres",
+      port: 5432,
+      parameters: [],
+      channel_name: "cluster"
+    ]
+  ]
+]

example/lib/example.ex

@@ -0,0 +1,8 @@
+defmodule Example do
+  use Application
+  def start(_type, _args) do
+    topologies = Application.get_env(:libcluster, :topologies)
+    children = [{Cluster.Supervisor, [topologies]}, NodeCheck]
+    Supervisor.start_link(children, strategy: :one_for_one)
+  end
+end

example/lib/node_check.ex

@@ -0,0 +1,16 @@
+defmodule NodeCheck do
+  use GenServer
+  require Logger
+  def start_link(_), do: GenServer.start_link(__MODULE__, [], name: __MODULE__)
+  def init(_) do
+    Process.send_after(self(), :check, 1_000)
+    {:ok, []}
+  end
+
+  def handle_info(:check, state) do
+    Logger.info("Connected nodes: #{inspect(Node.list())}", %{node: node()})
+    Process.send_after(self(), :check, 1_000)
+
+    {:noreply, state}
+  end
+end

example/mix.exs

@@ -0,0 +1,30 @@
+defmodule Example.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :example,
+      version: "0.1.0",
+      elixir: "~> 1.15",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger],
+      mod: {Example, []}
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      {:libcluster, "~> 3.3"},
+      {:postgrex, ">= 0.0.0"},
+      {:libcluster_postgres, path: "../"}
+    ]
+  end
+end

example/mix.lock

@@ -0,0 +1,8 @@
+%{
+  "db_connection": {:hex, :db_connection, "2.6.0", "77d835c472b5b67fc4f29556dee74bf511bbafecdcaf98c27d27fa5918152086", [:mix], [{:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "c2f992d15725e721ec7fbc1189d4ecdb8afef76648c746a8e1cad35e3b8a35f3"},
+  "decimal": {:hex, :decimal, "2.1.1", "5611dca5d4b2c3dd497dec8f68751f1f1a54755e8ed2a966c2633cf885973ad6", [:mix], [], "hexpm", "53cfe5f497ed0e7771ae1a475575603d77425099ba5faef9394932b35020ffcc"},
+  "jason": {:hex, :jason, "1.4.1", "af1504e35f629ddcdd6addb3513c3853991f694921b1b9368b0bd32beb9f1b63", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "fbb01ecdfd565b56261302f7e1fcc27c4fb8f32d56eab74db621fc154604a7a1"},
+  "libcluster": {:hex, :libcluster, "3.3.3", "a4f17721a19004cfc4467268e17cff8b1f951befe428975dd4f6f7b84d927fe0", [:mix], [{:jason, "~> 1.1", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "7c0a2275a0bb83c07acd17dab3c3bfb4897b145106750eeccc62d302e3bdfee5"},
+  "postgrex": {:hex, :postgrex, "0.17.3", "c92cda8de2033a7585dae8c61b1d420a1a1322421df84da9a82a6764580c503d", [:mix], [{:db_connection, "~> 2.1", [hex: :db_connection, repo: "hexpm", optional: false]}, {:decimal, "~> 1.5 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:table, "~> 0.1.0", [hex: :table, repo: "hexpm", optional: true]}], "hexpm", "946cf46935a4fdca7a81448be76ba3503cff082df42c6ec1ff16a4bdfbfb098d"},
+  "telemetry": {:hex, :telemetry, "1.2.1", "68fdfe8d8f05a8428483a97d7aab2f268aaff24b49e0f599faa091f1d4e7f61c", [:rebar3], [], "hexpm", "dad9ce9d8effc621708f99eac538ef1cbe05d6a874dd741de2e689c47feafed5"},
+}