feat: prometheus nixos module & test-container

for testing grafana in container
export QEMU_NET_OPTS="hostfwd=tcp::3000-:3000"
 nixos-rebuild build-vm --flake .#test-container
and then run the container, login is test/test

and the grafana port is forwarded to host machine, yay

.gitignore

@@ -4,3 +4,4 @@
 /result
 /routes/static/out.css
 /nixos.qcow2
+/data/

flake.nix

@@ -70,15 +70,33 @@
                   host = "some-automoderation.sunshine.industries";
                   useNginx = false;
                   port = 9090;
+                  metricsPort = 9091;
                   redisPort = 9999;
+                  enablePrometheus = true;
+                };
+                services.prometheus = {
+                  enable = true;
+                  port = 9998;
+                  # scrape config will be set up by the module
+                };
+                services.grafana = {
+                  enable = true;
+                  settings.server.http_port = 3000;
+                  settings.server.http_addr = "0.0.0.0";
+                  provision.datasources = {
+                    settings.datasources = [{
+                      name = "local-prometheus";
+                      type = "prometheus";
+                      url = "http://localhost:9998";
+                    }];
+                  };
                 };
               })
             ];
           };
         };
         nixosModules.some-automoderation-module = { lib, pkgs, config, ... }:
-          let
-            cfg = config.services.${pname};
+          let cfg = config.services.${pname};
           in {
             options.services.${pname} = {
               enable =
@@ -91,8 +109,7 @@
               useNginx = lib.mkOption {
                 type = lib.types.bool;
                 default = true;
-                description =
-                  "Whether to set up nginx reverse proxy";
+                description = "Whether to set up nginx reverse proxy";
               };
               port = lib.mkOption {
                 type = lib.types.int;
@@ -105,6 +122,16 @@
                 default = 7777;
                 description = "Port on which to connect to redis database.";
               };
+              metricsPort = lib.mkOption {
+                type = lib.types.int;
+                default = 8091;
+                description = "Port on which server exposes metrics.";
+              };
+              enablePrometheus = lib.mkOption {
+                type = lib.types.bool;
+                default = false;
+                description = "Whether to add scrape rules to prometheus";
+              };
               useHostTls = lib.mkOption {
                 type = lib.types.bool;
                 default = false;
@@ -112,12 +139,10 @@
                   "Whether virtual host should enable NixOS ACME certs";
               };
             };
-            config =
-              let
+            config = let
               username = "${pname}";
               groupname = "${pname}";
-            in
-              lib.mkIf cfg.enable {
+            in lib.mkIf cfg.enable {
               users.groups."${groupname}" = { };
               users.users."${username}" = {
                 isNormalUser = true; # needed to allow for home dir
@@ -131,8 +156,9 @@
                 startLimitBurst = 10;
                 serviceConfig = {
                   ExecStart = let
-                    serveCliArg =
-                      "--port ${toString cfg.port} --redisPort ${toString cfg.redisPort}";
+                    serveCliArg = "--port ${toString cfg.port} --redisPort ${
+                        toString cfg.redisPort
+                      } --metricsPort ${toString cfg.metricsPort}";
                   in "${packages.some-automoderation}/bin/${pname} ${serveCliArg}";
                   Restart = "on-failure";
                   User = "${username}";
@@ -157,10 +183,15 @@
                 enable = true;
                 user = "${username}";
                 port = cfg.redisPort;
-                settings = {
-                    notify-keyspace-events = "KEA";
-                  }
-                ;
+                settings = { notify-keyspace-events = "KEA"; };
+              };
+              services.prometheus = lib.mkIf cfg.enablePrometheus {
+                scrapeConfigs = [{
+                  job_name = "some-automoderation";
+                  static_configs = [{
+                    targets = [ "localhost:${toString cfg.metricsPort}" ];
+                  }];
+                }];
               };
             };
           };