modules/monitoring: Extract metrics from nginx logs

hosts/monitoring-3/prometheus.nix

@@ -52,6 +52,12 @@ let
     attrByPath ["clerie" "monitoring" "blackbox"] false host.config)
     monitoringHosts);
 
+  nginxlogMonitoringTargets = mapAttrsToList (name: host:
+    "${host.config.networking.hostName}.mon.clerie.de:9117")
+    (filterAttrs (name: host:
+    attrByPath ["services" "prometheus" "exporters" "nginxlog" "enable"] false host.config)
+    monitoringHosts);
+
   eachWithEachOther = (f: x: y: lib.lists.flatten (lib.lists.forEach x (a: lib.lists.forEach y (b: f a b))));
 
 in {
@@ -536,6 +542,18 @@ in {
           }
         ];
       }
+      {
+        job_name = "nginxlog-exporter";
+        scrape_interval = "20s";
+        static_configs = [
+          {
+            targets = nginxlogMonitoringTargets;
+          }
+        ];
+        relabel_configs = [
+          relabelAddressToInstance
+        ];
+      }
     ];
     alertmanagers = [
       {