feat: added clustering for spawn monitor

Author: Adriano Santos

spawn_monitor/.formatter.exs

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

spawn_monitor/.gitignore

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+# 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/
+
+# 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").
+spawn_monitor-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

spawn_monitor/README.md

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+# SpawnMonitor
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `spawn_monitor` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:spawn_monitor, "~> 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/spawn_monitor>.
+

spawn_monitor/config/config.exs

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+import Config
+
+config :spawn_monitor,
+  halt_on_abort: true,
+  namespace: SpawnMonitor
+
+# Configures the endpoint
+config :spawn_monitor, SpawnMonitorWeb.Endpoint,
+  url: [host: "localhost"],
+  render_errors: [view: SpawnMonitorWeb.ErrorView, accepts: ~w(json), layout: false],
+  pubsub_server: SpawnMonitor.PubSub,
+  live_view: [signing_salt: "kA47bW1N"]
+
+# Configures Elixir's Logger
+config :logger, :console,
+  format: "$time $metadata[$level] $message\n",
+  metadata: [:request_id]
+
+# Use Jason for JSON parsing in Phoenix
+config :phoenix, :json_library, Jason
+
+# Import environment specific config. This must remain at the bottom
+# of this file so it overrides the configuration defined above.
+import_config "#{config_env()}.exs"

spawn_monitor/config/dev.exs

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+import Config
+
+# For development, we disable any cache and enable
+# debugging and code reloading.
+#
+# The watchers configuration can be used to run external
+# watchers to your application. For example, we use it
+# with esbuild to bundle .js and .css sources.
+config :spawn_monitor, SpawnMonitorWeb.Endpoint,
+  debug_errors: true,
+  code_reloader: true,
+  check_origin: false,
+  secret_key_base: "1lFra0dpD7ayAn4I3NANdZTKZyd2ecunwvTQzKw+dIBsDZElo3i4cvRLhee3F/VL",
+  watchers: []
+
+config :spawn_monitor, :cookie, :my_cookie
+
+# Do not include metadata nor timestamps in development logs
+config :logger, :console, format: "[$level] $message\n"
+
+# Set a higher stacktrace during development. Avoid configuring such
+# in production as building large stacktraces may be expensive.
+config :phoenix, :stacktrace_depth, 20
+
+# Initialize plugs at runtime for faster development compilation
+config :phoenix, :plug_init_mode, :runtime

spawn_monitor/config/prod.exs

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+import Config
+
+# For production, don't forget to configure the url host
+# to something meaningful, Phoenix uses this information
+# when generating URLs.
+#
+# Note we also include the path to a cache manifest
+# containing the digested version of static files. This
+# manifest is generated by the `mix phx.digest` task,
+# which you should run after static files are built and
+# before starting your production server.
+config :spawn_monitor, SpawnMonitorWeb.Endpoint, server: true
+
+config :logger, level: :info

spawn_monitor/config/runtime.exs

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+import Config
+
+# config/runtime.exs is executed for all environments, including
+# during releases. It is executed after compilation and before the
+# system starts, so it is typically used to load production configuration
+# and secrets from environment variables or elsewhere. Do not define
+# any compile-time configuration in here, as it won't be applied.
+# The block below contains prod specific runtime configuration.
+if config_env() == :prod do
+  secret_key_base =
+    System.get_env("SPAWN_MONITOR_SECRET_KEY_BASE") ||
+      Base.encode64(:crypto.strong_rand_bytes(48))
+
+  config :spawn_monitor, SpawnMonitorWeb.Endpoint,
+    http: [
+      # Enable IPv6 and bind on all interfaces.
+      # Set it to  {0, 0, 0, 0, 0, 0, 0, 1} for local network only access.
+      # See the documentation on https://hexdocs.pm/plug_cowboy/Plug.Cowboy.html
+      # for details about using IPv6 vs IPv4 and loopback vs public addresses.
+      ip: {0, 0, 0, 0, 0, 0, 0, 0},
+      port: 8090
+    ],
+    secret_key_base: secret_key_base
+
+  # ## Using releases
+  #
+  # If you are doing OTP releases, you need to instruct Phoenix
+  # to start each relevant endpoint:
+  #
+  #     config :spawn_monitor, SpawnMonitorWeb.Endpoint, server: true
+  #
+  # Then you can assemble a release by calling `mix release`.
+  # See `mix help release` for more information.
+end

spawn_monitor/config/test.exs

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+import Config
+
+# We don't run a server during test. If one is required,
+# you can enable the server option below.
+config :spawn_monitor, SpawnMonitorWeb.Endpoint,
+  http: [ip: {127, 0, 0, 1}, port: 4002],
+  secret_key_base: "4uFwNlOnyppVcDWeVcNUgGPOYQD+y7F4mTkconBPSqAleqXvd2wmmcLCqXJanfon",
+  server: false
+
+config :spawn_monitor,
+  cookie: :"my-plds-test-cookie",
+  ensure_distribution?: false,
+  halt_on_abort: false
+
+# Print only warnings and errors during test
+config :logger, level: :warning
+
+# Initialize plugs at runtime for faster test compilation
+config :phoenix, :plug_init_mode, :runtime

spawn_monitor/lib/spawn_monitor.ex

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+defmodule SpawnMonitor do
+end

spawn_monitor/lib/spawn_monitor/application.ex

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+defmodule SpawnMonitor.Application do
+  @moduledoc false
+  use Application
+  require Logger
+
+  @impl true
+  def start(_type, _args) do
+    children = [
+      SpawnMonitor.Cluster.get_spec(),
+      {Phoenix.PubSub, name: SpawnMonitor.PubSub},
+      SpawnMonitorWeb.Endpoint
+    ]
+
+    opts = [strategy: :one_for_one, name: SpawnMonitor.Supervisor]
+    Supervisor.start_link(children, opts)
+  end
+
+  @impl true
+  def config_change(changed, _new, removed) do
+    SpawnMonitorWeb.Endpoint.config_change(changed, removed)
+    :ok
+  end
+end

spawn_monitor/lib/spawn_monitor/cluster.ex

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+defmodule SpawnMonitor.Cluster do
+  @moduledoc false
+  require Logger
+
+  import SpawnMonitor.Utils
+
+  def get_spec() do
+    cluster_strategy = env("PROXY_CLUSTER_STRATEGY", "gossip")
+
+    topologies =
+      case cluster_strategy do
+        "epmd" ->
+          get_epmd_strategy()
+
+        "gossip" ->
+          get_gossip_strategy()
+
+        "kubernetes-dns" ->
+          get_k8s_dns_strategy()
+
+        _ ->
+          Logger.warning("Invalid Topology")
+      end
+
+    if topologies && Code.ensure_compiled(Cluster.Supervisor) do
+      Logger.debug("Cluster topology #{inspect(topologies)}")
+
+      {Cluster.Supervisor,
+       [
+         topologies,
+         [name: String.to_atom("#{__MODULE__}.Cluster")]
+       ]}
+    end
+  end
+
+  defp get_epmd_strategy() do
+    [
+      proxy: [
+        strategy: Cluster.Strategy.Epmd
+      ]
+    ]
+  end
+
+  defp get_gossip_strategy() do
+    reuseaddr =
+      env("PROXY_CLUSTER_GOSSIP_REUSE_ADDRESS", "true")
+      |> to_bool()
+
+    broadcast_only =
+      env("PROXY_CLUSTER_GOSSIP_BROADCAST_ONLY", "true")
+      |> to_bool()
+
+    [
+      proxy: [
+        strategy: Cluster.Strategy.Gossip,
+        config: [
+          reuseaddr: reuseaddr,
+          multicast_addr: env("PROXY_CLUSTER_GOSSIP_MULTICAST_ADDRESS", "255.255.255.255"),
+          broadcast_only: broadcast_only
+        ]
+      ]
+    ]
+  end
+
+  defp get_k8s_dns_strategy() do
+    polling_interval =
+      env("PROXY_CLUSTER_POLLING", "3000")
+      |> String.to_integer()
+
+    [
+      proxy: [
+        strategy: Cluster.Strategy.Kubernetes.DNS,
+        config: [
+          service: env("PROXY_HEADLESS_SERVICE", "proxy-headless"),
+          application_name: "proxy",
+          polling_interval: polling_interval
+        ]
+      ]
+    ]
+  end
+end

spawn_monitor/lib/spawn_monitor/utils.ex

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+defmodule SpawnMonitor.Utils do
+  @moduledoc false
+
+  def env(key, default) when is_binary(key), do: System.get_env(key, default)
+
+  def to_bool("false"), do: false
+  def to_bool("true"), do: true
+  def to_bool(_), do: false
+end

spawn_monitor/lib/spawn_monitor_web.ex

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+defmodule SpawnMonitorWeb do
+  @moduledoc false
+
+  def controller do
+    quote do
+      use Phoenix.Controller, namespace: SpawnMonitorWeb
+      import Plug.Conn
+    end
+  end
+
+  def view do
+    quote do
+      use Phoenix.View,
+        root: "lib/spawn_monitor_web/templates",
+        namespace: SpawnMonitorWeb
+
+      import Phoenix.Controller,
+        only: [get_flash: 1, get_flash: 2, view_module: 1, view_template: 1]
+
+      unquote(view_helpers())
+    end
+  end
+
+  def router do
+    quote do
+      use Phoenix.Router
+
+      import Plug.Conn
+      import Phoenix.Controller
+    end
+  end
+
+  defp view_helpers do
+    quote do
+      import Phoenix.View
+    end
+  end
+
+  @doc """
+  When used, dispatch to the appropriate controller/view/etc.
+  """
+  defmacro __using__(which) when is_atom(which) do
+    apply(__MODULE__, which, [])
+  end
+end

spawn_monitor/lib/spawn_monitor_web/controllers/health_controller.ex

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+defmodule SpawnMonitorWeb.HealthController do
+  @moduledoc false
+  use SpawnMonitorWeb, :controller
+
+  def index(conn, _) do
+    version = Application.spec(:spawn_monitor, :vsn) |> List.to_string()
+
+    json(conn, %{
+      "application" => "spawn_monitor",
+      "version" => version
+    })
+  end
+end

spawn_monitor/lib/spawn_monitor_web/endpoint.ex

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+defmodule SpawnMonitorWeb.Endpoint do
+  @moduledoc false
+  use Phoenix.Endpoint, otp_app: :spawn_monitor
+
+  @session_options [
+    store: :cookie,
+    key: "_spawn_monitor_key",
+    signing_salt: "LVKEVz/+"
+  ]
+
+  socket("/live", Phoenix.LiveView.Socket,
+    # Don't check the origin as we don't know how the web app is gonna be accessed.
+    # It runs locally, but may be exposed via IP or domain name.
+    # The WebSocket connection is already protected from CSWSH by using CSRF token.
+    websocket: [check_origin: false, connect_info: [:user_agent, session: @session_options]]
+  )
+
+  if code_reloading? do
+    plug(Phoenix.CodeReloader)
+  end
+
+  plug(Phoenix.LiveDashboard.RequestLogger,
+    param_key: "request_logger",
+    cookie_key: "request_logger"
+  )
+
+  plug(Plug.MethodOverride)
+  plug(Plug.Head)
+  plug(Plug.Session, @session_options)
+  plug(SpawnMonitorWeb.Router)
+end