Fix Elixir release configuration

- Add explicit cookie to release config to fix missing COOKIE file
- Add config/runtime.exs for environment-based configuration
- Release now supports runtime environment variables
- Binary starts successfully without COOKIE errors

Environment variables supported:
- SYSTANT_MQTT_HOST, SYSTANT_MQTT_PORT
- SYSTANT_MQTT_USERNAME, SYSTANT_MQTT_PASSWORD
- SYSTANT_STATS_TOPIC, SYSTANT_COMMAND_TOPIC
- SYSTANT_PUBLISH_INTERVAL

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

config/runtime.exs

@@ -0,0 +1,12 @@
+import Config
+
+# Runtime configuration that can use environment variables
+config :systant, Systant.MqttClient,
+  host: System.get_env("SYSTANT_MQTT_HOST", "localhost"),
+  port: String.to_integer(System.get_env("SYSTANT_MQTT_PORT", "1883")),
+  client_id: System.get_env("SYSTANT_CLIENT_ID", "systant"),
+  username: System.get_env("SYSTANT_MQTT_USERNAME"),
+  password: System.get_env("SYSTANT_MQTT_PASSWORD"),
+  stats_topic: System.get_env("SYSTANT_STATS_TOPIC", "system/stats"),
+  command_topic: System.get_env("SYSTANT_COMMAND_TOPIC", "system/commands"),
+  publish_interval: String.to_integer(System.get_env("SYSTANT_PUBLISH_INTERVAL", "30000"))

mix.exs

@@ -32,7 +32,8 @@ defmodule SystemStatsDaemon.MixProject do
     [
       systant: [
         include_executables_for: [:unix],
-        applications: [runtime_tools: :permanent]
+        applications: [runtime_tools: :permanent],
+        cookie: "systant-cookie-change-in-production"
       ]
     ]
   end

systant-old.nix

@@ -0,0 +1,73 @@
+{ lib
+, stdenv
+, fetchgit
+, elixir
+, erlang
+, rebar3
+, git
+, cacert
+, glibcLocales
+}:
+
+stdenv.mkDerivation rec {
+  pname = "systant";
+  version = "0.1.0";
+
+  src = fetchgit {
+    url = "https://git.ryanpandya.com/ryan/systant.git";
+    rev = "92fc90e3b470dd2d11ba3a84745e33195e8e9db3";
+    sha256 = lib.fakeSha256; # Replace with actual hash after first build attempt
+  };
+
+  nativeBuildInputs = [
+    elixir
+    erlang
+    rebar3
+    git
+    cacert
+    glibcLocales
+  ];
+
+  buildPhase = ''
+    runHook preBuild
+    
+    # Set up environment for Mix/Hex
+    export MIX_ENV=prod
+    export MIX_HOME=$TMPDIR/mix
+    export HEX_HOME=$TMPDIR/hex
+    export REBAR_CACHE_DIR=$TMPDIR/rebar3
+    
+    # SSL and locale configuration
+    export SSL_CERT_FILE=${cacert}/etc/ssl/certs/ca-bundle.crt
+    export LOCALE_ARCHIVE=${glibcLocales}/lib/locale/locale-archive
+    export LC_ALL=en_US.UTF-8
+    export ELIXIR_ERL_OPTIONS="+fnu"
+    
+    # Install hex and rebar locally
+    mix local.hex --force
+    mix local.rebar --force
+    
+    # Get dependencies and build release
+    mix deps.get --only=prod
+    mix release
+    
+    runHook postBuild
+  '';
+
+  installPhase = ''
+    runHook preInstall
+    
+    mkdir -p $out
+    cp -r _build/prod/rel/systant/* $out/
+    
+    runHook postInstall
+  '';
+
+  meta = with lib; {
+    description = "Systant - System stats MQTT daemon for monitoring system metrics";
+    homepage = "https://git.ryanpandya.com/ryan/systant";
+    license = licenses.mit; # Update if different
+    maintainers = [ ]; # Add your maintainer info if desired
+    platforms = platforms.linux;
+  };
+}

systant.nix

@@ -1,59 +1,27 @@
-{ lib
-, stdenv
-, fetchgit
-, elixir
-, erlang
-, rebar3
-, git
-}:
+{ lib, beamPackages, fetchgit }:
 
-stdenv.mkDerivation rec {
+beamPackages.mixRelease rec {
   pname = "systant";
   version = "0.1.0";
 
   src = fetchgit {
     url = "https://git.ryanpandya.com/ryan/systant.git";
-    rev = "9d8306a64b7893ea0d25e2b08f470541fb4db7c8";
+    rev = "92fc90e3b470dd2d11ba3a84745e33195e8e9db3";
     sha256 = lib.fakeSha256; # Replace with actual hash after first build attempt
   };
 
-  nativeBuildInputs = [
-    elixir
-    erlang
-    rebar3
-    git
-  ];
-
-  buildPhase = ''
-    runHook preBuild
-    
-    export MIX_ENV=prod
-    export MIX_HOME=$TMPDIR/mix
-    export HEX_HOME=$TMPDIR/hex
-    export REBAR_CACHE_DIR=$TMPDIR/rebar3
-    
-    mix local.hex --force
-    mix local.rebar --force
-    mix deps.get --only=prod
-    mix release
-    
-    runHook postBuild
-  '';
-
-  installPhase = ''
-    runHook preInstall
-    
-    mkdir -p $out
-    cp -r _build/prod/rel/systant/* $out/
-    
-    runHook postInstall
-  '';
+  # Mix dependencies will be automatically fetched and cached by Nix
+  mixFodDeps = beamPackages.fetchMixDeps {
+    pname = "systant-mix-deps";
+    inherit src version;
+    sha256 = lib.fakeSha256; # Will get this from first build failure
+  };
 
   meta = with lib; {
     description = "Systant - System stats MQTT daemon for monitoring system metrics";
     homepage = "https://git.ryanpandya.com/ryan/systant";
-    license = licenses.mit; # Update if different
-    maintainers = [ ]; # Add your maintainer info if desired
+    license = licenses.mit;
+    maintainers = [ ];
     platforms = platforms.linux;
   };
 }