nixos/prometheus-keylight-exporter: new module

Signed-off-by: Matt Layher <mdlayher@gmail.com>

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

@@ -28,6 +28,7 @@ let
     "dovecot"
     "fritzbox"
     "json"
+    "keylight"
     "mail"
     "mikrotik"
     "minio"

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

@@ -0,0 +1,19 @@
+{ config, lib, pkgs, options }:
+
+with lib;
+
+let
+  cfg = config.services.prometheus.exporters.keylight;
+in
+{
+  port = 9288;
+  serviceOpts = {
+    serviceConfig = {
+      ExecStart = ''
+        ${pkgs.prometheus-keylight-exporter}/bin/keylight_exporter \
+          -metrics.addr ${cfg.listenAddress}:${toString cfg.port} \
+          ${concatStringsSep " \\\n  " cfg.extraFlags}
+      '';
+    };
+  };
+}

nixos/tests/prometheus-exporters.nix

@@ -202,6 +202,25 @@ let
       '';
     };
 
+    keylight = {
+      # A hardware device is required to properly test this exporter, so just
+      # perform a couple of basic sanity checks that the exporter is running
+      # and requires a target, but cannot reach a specified target.
+      exporterConfig = {
+        enable = true;
+      };
+      exporterTest = ''
+        wait_for_unit("prometheus-keylight-exporter.service")
+        wait_for_open_port(9288)
+        succeed(
+            "curl -sS --write-out '%{http_code}' -o /dev/null http://localhost:9288/metrics | grep -q '400'"
+        )
+        succeed(
+            "curl -sS --write-out '%{http_code}' -o /dev/null http://localhost:9288/metrics?target=nosuchdevice | grep -q '500'"
+        )
+      '';
+    };
+
     mail = {
       exporterConfig = {
         enable = true;