add node exporter

flake.nix

@@ -25,6 +25,12 @@
     in
     {
       formatter.${system} = pkgs.nixfmt-tree;
+      apps.${system}.connect = {
+        type = "app";
+        program = "${pkgs.writeShellScript "connect.sh" ''
+          ${pkgs.openssh}/bin/ssh root@matrix.berlin.ccc.de -L 3000:[::1]:3000 -L 9090:[::1]:9090 -N
+        ''}";
+      };
       devShells.${system}.default = pkgs.mkShell {
         packages = [
           (agenix.packages.${system}.default)

services/prometheus.nix

@@ -1,4 +1,4 @@
-{ pkgs, ... }:
+{ pkgs, lib, ... }:
 
 {
   services.prometheus = {
@@ -6,7 +6,10 @@
     retentionTime = "14d";
     listenAddress = "[::1]";
     exporters = {
-      #node = {};
+      node = {
+        enable = true;
+        listenAddress = services.prometheus.listenAddress;
+      };
       #nginx = {};
       #postgres = {};
     };
@@ -16,10 +19,21 @@
         scrape_interval = "15s";
         static_configs = [
           {
-            targets = [ "[::1]:9009" ];
+            target = lib.pipe config.services.matrix-synapse.settings.listeners [
+              (lib.filter (l: l.type == "metrics"))
+              builtins.head
+              (l: "[${l.listenAddress}]:${l.port}")
+            ];
           }
         ];
       }
+      {
+        job_name = "node";
+        scrape_interval = "15s";
+        static_configs = [
+          { targets = [ "${config.services.prometheus.exporters.node.listenAddress}:${toString config.services.prometheus.exporters.node.port}" ]; }
+        ];
+      }
     ];
     ruleFiles = [
       # https://github.com/element-hq/synapse/tree/master/contrib/prometheus