modules/monitoring: Extract metrics from nginx logs

modules/monitoring/default.nix

@@ -102,6 +102,33 @@ in
       listen = "[::]:9152";
     };
 
+    services.prometheus.exporters.nginxlog = mkIf config.services.nginx.enable {
+      enable = true;
+      settings = {
+        namespaces = [
+          {
+            name = "nginxlog";
+            format = ''$host: $remote_addr - $remote_user [$time_local] "$request" $status $body_bytes_sent "$http_referer" "$http_user_agent" "$server_name" rt="$request_time" uct="$upstream_connect_time" uht="$upstream_header_time" urt="$upstream_response_time"'';
+            source = {
+              files = [
+                "/var/log/nginx/access.log"
+              ];
+            };
+            relabel_configs = [
+              {
+                target_label = "server_name";
+                from = "server_name";
+              }
+            ];
+          }
+        ];
+      };
+    };
+
+    systemd.services."prometheus-nginxlog-exporter".serviceConfig = {
+      SupplementaryGroups = "nginx";
+    };
+
     networking.firewall.interfaces."wg-monitoring".allowedTCPPorts = [
       9100 # node-exporter
       9152 # nixos-exporter
@@ -109,6 +136,8 @@ in
       9324 # bird-exporter
     ] else []) ++ (if cfg.blackbox then [
       9115 # blackbox-exporter
+    ] else []) ++ (if config.services.prometheus.exporters.nginxlog.enable then [
+      config.services.prometheus.exporters.nginxlog.port
     ] else []);
   };
 }