nixos/prometheus: add script exporter

nixos/modules/services/monitoring/prometheus/exporters.nix

@@ -55,6 +55,7 @@ let
     "redis"
     "rspamd"
     "rtl_433"
+    "script"
     "snmp"
     "smokeping"
     "sql"

nixos/modules/services/monitoring/prometheus/exporters/script.nix

@@ -0,0 +1,64 @@
+{ config, lib, pkgs, options }:
+
+with lib;
+
+let
+  cfg = config.services.prometheus.exporters.script;
+  configFile = pkgs.writeText "script-exporter.yaml" (builtins.toJSON cfg.settings);
+in
+{
+  port = 9172;
+  extraOpts = {
+    settings.scripts = mkOption {
+      type = with types; listOf (submodule {
+        options = {
+          name = mkOption {
+            type = str;
+            example = "sleep";
+            description = "Name of the script.";
+          };
+          script = mkOption {
+            type = str;
+            example = "sleep 5";
+            description = "Shell script to execute when metrics are requested.";
+          };
+          timeout = mkOption {
+            type = nullOr int;
+            default = null;
+            example = 60;
+            description = "Optional timeout for the script in seconds.";
+          };
+        };
+      });
+      example = literalExample ''
+        {
+          scripts = [
+            { name = "sleep"; script = "sleep 5"; }
+          ];
+        }
+      '';
+      description = ''
+        All settings expressed as an Nix attrset.
+
+        Check the official documentation for the corresponding YAML
+        settings that can all be used here: <link xlink:href="https://github.com/adhocteam/script_exporter#sample-configuration" />
+      '';
+    };
+  };
+  serviceOpts = {
+    serviceConfig = {
+      ExecStart = ''
+        ${pkgs.prometheus-script-exporter}/bin/script_exporter \
+          --web.listen-address ${cfg.listenAddress}:${toString cfg.port} \
+          --config.file ${configFile} \
+          ${concatStringsSep " \\\n  " cfg.extraFlags}
+      '';
+      NoNewPrivileges = true;
+      ProtectHome = true;
+      ProtectSystem = "strict";
+      ProtectKernelTunables = true;
+      ProtectKernelModules = true;
+      ProtectControlGroups = true;
+    };
+  };
+}

nixos/tests/prometheus-exporters.nix

@@ -945,6 +945,24 @@ let
       '';
     };
 
+    script = {
+      exporterConfig = {
+        enable = true;
+        settings.scripts = [
+          { name = "success"; script = "sleep 1"; }
+        ];
+      };
+      exporterTest = ''
+        wait_for_unit("prometheus-script-exporter.service")
+        wait_for_open_port(9172)
+        wait_until_succeeds(
+            "curl -sSf 'localhost:9172/probe?name=success' | grep -q '{}'".format(
+                'script_success{script="success"} 1'
+            )
+        )
+      '';
+    };
+
     smokeping = {
       exporterConfig = {
         enable = true;