nixos/prometheus: add process exporter

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

···
     "pihole"
     "postfix"
     "postgres"
+    "process"
     "py-air-control"
     "redis"
     "rspamd"

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

···
+{ config, lib, pkgs, options }:
+
+with lib;
+
+let
+  cfg = config.services.prometheus.exporters.process;
+  configFile = pkgs.writeText "process-exporter.yaml" (builtins.toJSON cfg.settings);
+in
+{
+  port = 9256;
+  extraOpts = {
+    settings.process_names = mkOption {
+      type = types.listOf types.anything;
+      default = {};
+      example = literalExample ''
+        {
+          process_names = [
+            # Remove nix store path from process name
+            { name = "{{.Matches.Wrapped}} {{ .Matches.Args }}"; cmdline = [ "^/nix/store[^ ]*/(?P<Wrapped>[^ /]*) (?P<Args>.*)" ]; }
+          ];
+        }
+      '';
+      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/ncabatoff/process-exporter" />
+      '';
+    };
+  };
+  serviceOpts = {
+    serviceConfig = {
+      DynamicUser = false;
+      ExecStart = ''
+        ${pkgs.prometheus-process-exporter}/bin/process-exporter \
+          --web.listen-address ${cfg.listenAddress}:${toString cfg.port} \
+          --config.path ${configFile} \
+          ${concatStringsSep " \\\n  " cfg.extraFlags}
+      '';
+      NoNewPrivileges = true;
+      ProtectHome = true;
+      ProtectSystem = true;
+      ProtectKernelTunables = true;
+      ProtectKernelModules = true;
+      ProtectControlGroups = true;
+    };
+  };
+}

nixos/tests/prometheus-exporters.nix

···
       '';
     };
 
+    process = {
+      exporterConfig = {
+        enable = true;
+        settings.process_names = [
+          # Remove nix store path from process name
+          { name = "{{.Matches.Wrapped}} {{ .Matches.Args }}"; cmdline = [ "^/nix/store[^ ]*/(?P<Wrapped>[^ /]*) (?P<Args>.*)" ]; }
+        ];
+      };
+      exporterTest = ''
+        wait_for_unit("prometheus-process-exporter.service")
+        wait_for_open_port(9256)
+        wait_until_succeeds(
+            "curl -sSf localhost:9256/metrics | grep -q '{}'".format(
+                'namedprocess_namegroup_cpu_seconds_total{groupname="process-exporter '
+            )
+        )
+      '';
+    };
+
     py-air-control = {
       nodeName = "py_air_control";
       exporterConfig = {

pkgs/servers/monitoring/prometheus/process-exporter.nix

···
-{ lib, buildGoModule, fetchFromGitHub }:
+{ lib, buildGoModule, fetchFromGitHub, nixosTests }:
 
 buildGoModule rec {
   pname = "process-exporter";
···
   '';
 
   doCheck = true;
+
+  passthru.tests = { inherit (nixosTests.prometheus-exporters) process; };
 
   meta = with lib; {
     description = "Prometheus exporter that mines /proc to report on selected processes";