nixos: add prometheus_nginxlog_exporter module + test

nixos/modules/services/monitoring/prometheus/exporters.nix

@@ -37,6 +37,7 @@ let
     "modemmanager"
     "nextcloud"
     "nginx"
+    "nginxlog"
     "node"
     "openvpn"
     "postfix"

nixos/modules/services/monitoring/prometheus/exporters/nginxlog.nix

@@ -0,0 +1,51 @@
+{ config, lib, pkgs, options }:
+
+with lib;
+
+let
+  cfg = config.services.prometheus.exporters.nginxlog;
+in {
+  port = 9117;
+  extraOpts = {
+    settings = mkOption {
+      type = types.attrs;
+      default = {};
+      description = ''
+        All settings of nginxlog expressed as an Nix attrset.
+
+        Check the official documentation for the corresponding YAML
+        settings that can all be used here: https://github.com/martin-helmich/prometheus-nginxlog-exporter
+
+        The `listen` object is already generated by `port`, `listenAddress` and `metricsEndpoint` and
+        will be merged with the value of `settings` before writting it as JSON.
+      '';
+    };
+
+    metricsEndpoint = mkOption {
+      type = types.str;
+      default = "/metrics";
+      description = ''
+        Path under which to expose metrics.
+      '';
+    };
+  };
+
+  serviceOpts = let
+    listenConfig = {
+      listen = {
+        port = cfg.port;
+        address = cfg.listenAddress;
+        metrics_endpoint = cfg.metricsEndpoint;
+      };
+    };
+    completeConfig = pkgs.writeText "nginxlog-exporter.yaml" (builtins.toJSON (lib.recursiveUpdate listenConfig cfg.settings));
+  in {
+    serviceConfig = {
+      ExecStart = ''
+        ${pkgs.prometheus-nginxlog-exporter}/bin/prometheus-nginxlog-exporter -config-file ${completeConfig}
+      '';
+      Restart="always";
+      ProtectSystem="full";
+    };
+  };
+}

nixos/tests/prometheus-exporters.nix

@@ -444,6 +444,67 @@ let
       '';
     };
 
+    nginxlog = {
+      exporterConfig = {
+        enable = true;
+        group = "nginx";
+        settings = {
+          namespaces = [
+            {
+              name = "filelogger";
+              source = {
+                files = [ "/var/log/nginx/filelogger.access.log" ];
+              };
+            }
+            {
+              name = "syslogger";
+              source = {
+                syslog = {
+                  listen_address = "udp://127.0.0.1:10000";
+                  format = "rfc3164";
+                  tags = ["nginx"];
+                };
+              };
+            }
+          ];
+        };
+      };
+      metricProvider = {
+        services.nginx = {
+          enable = true;
+          httpConfig = ''
+            server {
+              listen 80;
+              server_name filelogger.local;
+              access_log /var/log/nginx/filelogger.access.log;
+            }
+            server {
+              listen 81;
+              server_name syslogger.local;
+              access_log syslog:server=127.0.0.1:10000,tag=nginx,severity=info;
+            }
+          '';
+        };
+      };
+      exporterTest = ''
+        wait_for_unit("nginx.service")
+        wait_for_unit("prometheus-nginxlog-exporter.service")
+        wait_for_open_port(9117)
+        wait_for_open_port(80)
+        wait_for_open_port(81)
+        succeed("curl http://localhost")
+        execute("sleep 1")
+        succeed(
+            "curl -sSf http://localhost:9117/metrics | grep 'filelogger_http_response_count_total' | grep -q 1"
+        )
+        succeed("curl http://localhost:81")
+        execute("sleep 1")
+        succeed(
+            "curl -sSf http://localhost:9117/metrics | grep 'syslogger_http_response_count_total' | grep -q 1"
+        )
+      '';
+    };
+
     node = {
       exporterConfig = {
         enable = true;

pkgs/servers/monitoring/prometheus/nginxlog-exporter.nix

@@ -1,4 +1,4 @@
-{ stdenv, buildGoModule, fetchFromGitHub }:
+{ stdenv, buildGoModule, fetchFromGitHub, nixosTests }:
 
 buildGoModule rec {
   pname = "nginxlog_exporter";
@@ -17,6 +17,8 @@ buildGoModule rec {
 
   runVend = true;
 
+  passthru.tests = { inherit (nixosTests.prometheus-exporters) nginxlog; };
+
   meta = with stdenv.lib; {
     description = "Export metrics from Nginx access log files to Prometheus";
     homepage = "https://github.com/martin-helmich/prometheus-nginxlog-exporter";