service/jellyfin: enable metrics

modules/services/jellyfin/default.nix

@@ -4,6 +4,11 @@ let
   cfg = config.my.services.jellyfin;
   domain = config.networking.domain;
   port = 8096;
+  # enable monitoring
+  jellyfin-with-metrics = pkgs.jellyfin.overrideAttrs (attrs: {
+    # with this patch the default setting for metrics is changed
+    patches = attrs.patches ++ [ ./enable-metrics.patch ];
+  });
 in
 {
   options.my.services.jellyfin = with lib; {
@@ -13,8 +18,26 @@ in
   config = lib.mkIf cfg.enable {
     services.jellyfin = {
       enable = true;
+      package = jellyfin-with-metrics;
     };
 
+    services.prometheus = {
+      scrapeConfigs = [
+        {
+          job_name = "jellyfin";
+          static_configs = [
+            {
+              targets = [ "127.0.0.1:${toString cfg.port}" ];
+              labels = {
+                instance = config.networking.hostName;
+              };
+            }
+          ];
+        }
+      ];
+    };
+    # sadly the metrics do not contain application specific metrics, only c# -> no dashboard
+
     my.services.nginx.virtualHosts = [
       {
         subdomain = "media";

modules/services/jellyfin/enable-metrics.patch

@@ -0,0 +1,13 @@
+diff --git a/MediaBrowser.Model/Configuration/ServerConfiguration.cs b/MediaBrowser.Model/Configuration/ServerConfiguration.cs
+index 07f02d1879..0f1c2e0cb8 100644
+--- a/MediaBrowser.Model/Configuration/ServerConfiguration.cs
++++ b/MediaBrowser.Model/Configuration/ServerConfiguration.cs
+@@ -66,7 +66,7 @@ namespace MediaBrowser.Model.Configuration
+         /// <summary>
+         /// Gets or sets a value indicating whether to enable prometheus metrics exporting.
+         /// </summary>
+-        public bool EnableMetrics { get; set; } = false;
++        public bool EnableMetrics { get; set; } = true;
+ 
+         public bool EnableNormalizedItemByNameIds { get; set; } = true;
+