hosts/nachtigall/apps/matrix/synapse.nix

@@ -55,7 +55,6 @@ in
               compress = false;
               names = [
                 "federation"
-                "metrics"
               ];
             }
           ];
@@ -63,6 +62,20 @@ in
           type = "http";
           x_forwarded = true;
         }
+        {
+          bind_addresses = [
+            "127.0.0.1"
+          ];
+          port = 8012;
+          resources = [
+            {
+              names = [
+                "metrics"
+              ];
+            }
+          ];
+          type = "metrics";
+        }
       ];
 
       account_threepid_delegates.msisdn = "";

hosts/nachtigall/apps/nginx-prometheus-exporters.nix

@@ -1,7 +1,14 @@
 { config, flake, lib, ... }:
 let
-  # Get port from first element in list of matrix-synapse listeners
+  # Find element in list config.services.matrix-synapse.settings.listeners
-  synapsePort = "${toString (lib.findFirst (listener: listener.port != null) "" config.services.matrix-synapse.settings.listeners).port}";
+  # that sets type = "metrics"
+  listenerWithMetrics = lib.findFirst
+    (listener:
+      listener.type == "metrics")
+    (throw "Found no matrix-synapse.settings.listeners.*.type containing string metrics")
+    config.services.matrix-synapse.settings.listeners
+  ;
+  synapseMetricsPort = "${toString listenerWithMetrics.port}";
 in
 {
   age.secrets.nachtigall-metrics-nginx-basic-auth = {
@@ -18,7 +25,7 @@ in
         proxyPass = "http://127.0.0.1:${toString(config.services.prometheus.exporters.node.port)}";
       };
       locations."/_synapse/metrics" = {
-        proxyPass = "http://127.0.0.1:${synapsePort}";
+        proxyPass = "http://127.0.0.1:${synapseMetricsPort}";
       };
     };
   };