From 9dd18e2cdc6ebafd8f0a27d513d54fe9fefa0067 Mon Sep 17 00:00:00 2001
From: Luke Granger-Brown <hg@lukegb.com>
Date: Mon, 11 Jan 2021 17:44:23 +0000
Subject: [PATCH] ops/nixos/lib/common: add
 nixos_running_system/nixos_booted_system node metrics

---
 ops/nixos/lib/common.nix | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/ops/nixos/lib/common.nix b/ops/nixos/lib/common.nix
index 43b79c56ae..1fbcbf4330 100644
--- a/ops/nixos/lib/common.nix
+++ b/ops/nixos/lib/common.nix
@@ -149,7 +149,26 @@ in
 
     services.prometheus.exporters.node = {
       enable = true;
-      enabledCollectors = [ "systemd" ];
+      enabledCollectors = [ "systemd" "textfile" ];
+      extraFlags = [
+        "--collector.textfile.directory=/run/prometheus-textfile-exports"
+      ];
     };
+    system.activationScripts.node-exporter = {
+      text = ''
+        test -d /run/prometheus-textfile-exports || mkdir /run/prometheus-textfile-exports
+        my_version_string="$(cat "$systemConfig/nixos-version")"
+        echo "nixos_running_system{version=\"$my_version_string\"} 1" > /run/prometheus-textfile-exports/running_system.prom
+      '';
+    };
+    boot.postBootCommands = lib.mkAfter ''
+      test -d /run/prometheus-textfile-exports || mkdir /run/prometheus-textfile-exports
+      my_version_string="$(cat "/run/booted-system/nixos-version")"
+      echo "nixos_booted_system{version=\"$my_version_string\"} 1" > /run/prometheus-textfile-exports/booted_system.prom
+    '';
+
+    system.nixos.tags = lib.mkBefore [
+      depot.version
+    ];
   };
 }