Remove unused support for initial peers

.envrc

@@ -1,4 +1,4 @@
 use flake
 
-export RELEASE_NODE=frajtano-test@
+export RELEASE_NODE=frajtano-test@$(cat /etc/hostname)
 export FRAJTANO_DIR=$PWD/.frajtano_state

config/runtime.exs

@@ -1,6 +1,5 @@
 import Config
+
 config :frajtano,
-  listen_path: Path.expand(System.get_env("FRAJTANO_DIR")) |> Path.join("agent.sock"),
-  initial_peers: System.get_env("FRAJTANO_PEERS", "") |> String.split(":", trim: true) |> Enum.map(&Path.expand/1)
-                
+  listen_path: Path.expand(System.get_env("FRAJTANO_DIR")) |> Path.join("agent.sock")
 

default.nix

@@ -3,9 +3,10 @@
   pkgs,
   mixRelease,
   elixir,
+  fetchMixDeps,
 }: let
   pname = "frajtano";
-  pkg = mixRelease {
+  pkg = mixRelease rec {
     inherit pname;
     version = "0.0.1";
 
@@ -16,6 +17,18 @@
       filter = path: _type: baseNameOf path != "flake.nix" && baseNameOf path != "flake.lock";
     };
 
+    # Adapted from https://blog.eigenvalue.net/nix-rerunning-fixed-output-derivations/
+    # deps hash should change any time ./mix.lock changes, and not otherwise
+    mixFodDeps = let
+      deps = fetchMixDeps {
+        pname = "mix-deps-${pname}";
+        inherit version src;
+        sha256 = "sha256-4g5lUlr5+l+mNVp0InZkx6X31g2cckI8NNQp37QgBis=";
+      };
+      hash = builtins.substring 11 32 "${./mix.lock}";
+    in
+      deps.overrideAttrs (attrs: {name = "${deps.name}-${hash}";});
+
     ELIXIR_MAKE_CACHE_DIR = "/tmp/.elixir-make-cache";
     meta.mainProgram = pname;
   };
@@ -25,14 +38,24 @@
     file="$FRAJTANO_DIR/cookie"
     (umask 077; [ -f "$file" ] || ${pkgs.coreutils}/bin/head -c 128 /dev/urandom | ${pkgs.coreutils}/bin/base64 -w0 > "$file")
     export RELEASE_COOKIE=$(${pkgs.coreutils}/bin/cat "$file")
-    export RELEASE_NODE="frajtano-$(${pkgs.coreutils}/bin/whoami)@$(${pkgs.coreutils}/bin/cat /etc/hostname)"
+    [ -n $RELEASE_NODE ] || export RELEASE_NODE="frajtano-$(${pkgs.coreutils}/bin/whoami)@$(${pkgs.coreutils}/bin/cat /etc/hostname)"
     run() {
       exec ${lib.getExe pkg} "$@"
     }
 
+    list() {
+      for i in "$@"; do
+        echo "\"$i\", "
+      done
+    }
+
     case "''${1:-}" in
       assimilate)
-        run rpc ":ok = \"$(echo -n "$2" | ${pkgs.coreutils}/bin/base64)\" |> Base.decode64!() |> Frajtano.Agent.add_peer()"
+        run rpc ":ok = \"$(echo -n "$2" | ${pkgs.coreutils}/bin/base64)\" |> Base.decode64!() |> Frajtano.Agent.assimilate()"
+      ;;
+      spawn)
+        shift
+        run rpc ":ok = Frajtano.Agent.spawn_peer({\"/usr/bin/env\", [$(list "$@")]})"
       ;;
       socket)
         echo $FRAJTANO_DIR/agent.sock
@@ -42,4 +65,9 @@
       ;;
     esac
   '';
-in pkgs.symlinkJoin { name = pname; paths = [ script pkg ]; meta.mainProgram = pname; }
+in
+  pkgs.symlinkJoin {
+    name = pname;
+    paths = [script pkg];
+    meta.mainProgram = pname;
+  }

lib/agent.ex

@@ -11,16 +11,9 @@ defmodule Frajtano.Agent do
     {
       :ok,
       %{},
-      {:continue, :init_peers}
     }
   end
 
-  @impl true
-  def handle_continue(:init_peers, state) do
-    for peer <- Application.fetch_env!(:frajtano, :initial_peers), do: {:ok, _} = Peer.start(peer)
-    {:noreply, state}
-  end
-
   # select: list of specs, where specs are a tuple of match, guards, and outputs
   # match is {key, pid, value}, :"$1" is a match variable
   def peer_paths() do
@@ -56,9 +49,8 @@ defmodule Frajtano.Agent do
   end
 
   @impl true
-  def handle_call({:add_peer, path}, _from, state) do
-    # TODO: deduplicate peers by socket path
-    case Peer.start(path) do
+  def handle_call({:add_peer, spec}, _from, state) do
+    case Peer.start(spec) do
       {:ok, _} -> {:reply, :ok, state}
       {:error, error} -> {:reply, {:error, error}, state}
     end
@@ -73,7 +65,11 @@ defmodule Frajtano.Agent do
     GenServer.call(__MODULE__, {:sign, request}, :infinity)
   end
 
-  def add_peer(path) do
-    GenServer.call(__MODULE__, {:add_peer, path})
+  def assimilate(path) do
+    GenServer.call(__MODULE__, {:add_peer, {:socket, path}})
+  end
+
+  def spawn_peer(spec) do
+    GenServer.call(__MODULE__, {:add_peer, {:spawn, spec}}) 
   end
 end

lib/peer.ex

@@ -3,20 +3,59 @@ defmodule Frajtano.Peer do
   require Logger
   use GenServer, restart: :temporary
 
-  def start(path) do
-    DynamicSupervisor.start_child(Frajtano.PeerSupervisor, {__MODULE__, path})
+  defmodule Spawner do
+    use Supervisor, restart: :permanent
+
+    def start_link(spec) do
+      Supervisor.start_link(__MODULE__, spec, [])
+    end
+
+    @impl true
+    def init({executable, args}) do
+      Temp.track!()
+      path = Path.join(Temp.mkdir!(), "agent.sock")
+
+      children = [
+        Supervisor.child_spec({MuonTrap.Daemon, [executable, args ++ [path]]}, restart: :temporary, significant: true),
+        Supervisor.child_spec({Frajtano.Peer, {path, :spawned, {executable, args}}}, restart: :permanent)
+      ]
+
+      Supervisor.init(children, strategy: :one_for_all, auto_shutdown: :any_significant)
+    end
   end
 
-  def start_link(path) do
-    GenServer.start_link(__MODULE__, path, name: {:via, Registry, {Frajtano.Peers, path}})
+  def start({:socket, path}) do
+    DynamicSupervisor.start_child(Frajtano.PeerSupervisor, {__MODULE__, {path}})
+  end
+
+  def start({:spawn, spec}) do
+    DynamicSupervisor.start_child(Frajtano.PeerSupervisor, {Spawner, spec})
+  end
+
+  def start_link({path}) do
+    GenServer.start_link(__MODULE__, {path}, name: {:via, Registry, {Frajtano.Peers, path}})
+  end
+  def start_link({_, _, _} = spec) do
+    GenServer.start_link(__MODULE__, spec, name: {:via, Registry, {Frajtano.Peers, spec}})
   end
 
   @impl true
-  def init(path) do
+  def init({path}) do
     {:ok, conn} = :gen_tcp.connect({:local, path}, 0, [:binary, active: :once])
     {:ok, %{conn: conn, clients: :queue.new(), buffer: <<>>}}
   end
 
+  @impl true
+  def init({path, :spawned, _}) do
+    if File.exists?(path) do
+      {:ok, conn} = :gen_tcp.connect({:local, path}, 0, [:binary, active: :once])
+      {:ok, %{conn: conn, clients: :queue.new(), buffer: <<>>}}
+    else
+      Process.sleep(100)
+      init({path, :spawned, nil})
+    end
+  end
+
   def reply({client, ref}, msg) do
     send(client, {ref, msg})
   end

mix.exs

@@ -19,6 +19,9 @@ defmodule Frajtano.MixProject do
   end
 
   defp deps do
-    []
+    [
+      {:muontrap, "~> 1.0"},
+      {:temp, "~> 0.4"},
+    ]
   end
 end

mix.lock

@@ -1 +1,5 @@
-
+%{
+  "elixir_make": {:hex, :elixir_make, "0.8.4", "4960a03ce79081dee8fe119d80ad372c4e7badb84c493cc75983f9d3bc8bde0f", [:mix], [{:castore, "~> 0.1 or ~> 1.0", [hex: :castore, repo: "hexpm", optional: true]}, {:certifi, "~> 2.0", [hex: :certifi, repo: "hexpm", optional: true]}], "hexpm", "6e7f1d619b5f61dfabd0a20aa268e575572b542ac31723293a4c1a567d5ef040"},
+  "muontrap": {:hex, :muontrap, "1.5.0", "bf5c273872379968615a39974458328209ac97fa1f588396192131ff973d1ca2", [:make, :mix], [{:elixir_make, "~> 0.6", [hex: :elixir_make, repo: "hexpm", optional: false]}], "hexpm", "daf605e877f60b5be9215e3420d7971fc468677b29921e40915b15fd928273d4"},
+  "temp": {:hex, :temp, "0.4.9", "eb6355bfa7925a568b3d9eb3bb57e89aa6d2b78bfe8dfb6b698e090631b7f41f", [:mix], [], "hexpm", "bc8bf7b27d9105bef933ef4bf4ba37ac6b899dbeba329deaa88c60b62d6b4b6d"},
+}