nixos/prometheus-nextcloud-exporter: add module

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

@@ -30,6 +30,7 @@ let
     "json"
     "mail"
     "minio"
+    "nextcloud"
     "nginx"
     "node"
     "postfix"

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

@@ -0,0 +1,58 @@
+{ config, lib, pkgs, options }:
+
+with lib;
+
+let
+  cfg = config.services.prometheus.exporters.nextcloud;
+in
+{
+  port = 9205;
+  extraOpts = {
+    url = mkOption {
+      type = types.str;
+      example = "https://domain.tld";
+      description = ''
+        URL to the Nextcloud serverinfo page.
+        Adding the path to the serverinfo API is optional, it defaults
+        to <literal>/ocs/v2.php/apps/serverinfo/api/v1/info</literal>.
+      '';
+    };
+    username = mkOption {
+      type = types.str;
+      default = "nextcloud-exporter";
+      description = ''
+        Username for connecting to Nextcloud.
+        Note that this account needs to have admin privileges in Nextcloud.
+      '';
+    };
+    passwordFile = mkOption {
+      type = types.path;
+      example = "/path/to/password-file";
+      description = ''
+        File containing the password for connecting to Nextcloud.
+        Make sure that this file is readable by the exporter user.
+      '';
+    };
+    timeout = mkOption {
+      type = types.str;
+      default = "5s";
+      description = ''
+        Timeout for getting server info document.
+      '';
+    };
+  };
+  serviceOpts = {
+    serviceConfig = {
+      DynamicUser = false;
+      ExecStart = ''
+        ${pkgs.prometheus-nextcloud-exporter}/bin/nextcloud-exporter \
+          -a ${cfg.listenAddress}:${toString cfg.port} \
+          -u ${cfg.username} \
+          -t ${cfg.timeout} \
+          -l ${cfg.url} \
+          -p @${cfg.passwordFile} \
+          ${concatStringsSep " \\\n  " cfg.extraFlags}
+      '';
+    };
+  };
+}