Merge pull request #242365 from h7x4/add-mysqld-exporter

services/prometheus/exporters: add mysqld

nixos/doc/manual/release-notes/rl-2311.section.md

@@ -30,6 +30,8 @@
 
 - [Anuko Time Tracker](https://github.com/anuko/timetracker), a simple, easy to use, open source time tracking system. Available as [services.anuko-time-tracker](#opt-services.anuko-time-tracker.enable).
 
+- [Prometheus MySQL exporter](https://github.com/prometheus/mysqld_exporter), a MySQL server exporter for Prometheus. Available as [services.prometheus.exporters.mysqld](#opt-services.prometheus.exporters.mysqld.enable).
+
 - [sitespeed-io](https://sitespeed.io), a tool that can generate metrics (timings, diagnostics) for websites. Available as [services.sitespeed-io](#opt-services.sitespeed-io.enable).
 
 - [Jool](https://nicmx.github.io/Jool/en/index.html), an Open Source implementation of IPv4/IPv6 translation on Linux. Available as [networking.jool.enable](#opt-networking.jool.enable).

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

@@ -50,6 +50,7 @@ let
     "mikrotik"
     "minio"
     "modemmanager"
+    "mysqld"
     "nextcloud"
     "nginx"
     "nginxlog"
@@ -296,6 +297,12 @@ in
         Please specify either 'services.prometheus.exporters.mail.configuration'
           or 'services.prometheus.exporters.mail.configFile'.
       '';
+    } {
+      assertion = cfg.mysqld.runAsLocalSuperUser -> config.services.mysql.enable;
+      message = ''
+        The exporter is configured to run as 'services.mysql.user', but
+          'services.mysql.enable' is set to false.
+      '';
     } {
       assertion = cfg.sql.enable -> (
         (cfg.sql.configFile == null) != (cfg.sql.configuration == null)

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

@@ -0,0 +1,60 @@
+{ config, lib, pkgs, options }:
+let
+  cfg = config.services.prometheus.exporters.mysqld;
+  inherit (lib) types mkOption mdDoc mkIf mkForce cli concatStringsSep optionalString escapeShellArgs;
+in {
+  port = 9104;
+  extraOpts = {
+    telemetryPath = mkOption {
+      type = types.str;
+      default = "/metrics";
+      description = mdDoc ''
+        Path under which to expose metrics.
+      '';
+    };
+
+    runAsLocalSuperUser = mkOption {
+      type = types.bool;
+      default = false;
+      description = mdDoc ''
+        Whether to run the exporter as {option}`services.mysql.user`.
+      '';
+    };
+
+    configFile = mkOption {
+      type = types.path;
+      example = "/var/lib/prometheus-mysqld-exporter.cnf";
+      description = mdDoc ''
+        Path to the services config file.
+
+        See <https://github.com/prometheus/mysqld_exporter#running> for more information about
+        the available options.
+
+        ::: {.warn}
+        Please do not store this file in the nix store if you choose to include any credentials here,
+        as it would be world-readable.
+        :::
+      '';
+    };
+  };
+
+  serviceOpts = {
+    serviceConfig = {
+      DynamicUser = !cfg.runAsLocalSuperUser;
+      User = mkIf cfg.runAsLocalSuperUser (mkForce config.services.mysql.user);
+      LoadCredential = mkIf (cfg.configFile != null) (mkForce ("config:" + cfg.configFile));
+      ExecStart = concatStringsSep " " [
+        "${pkgs.prometheus-mysqld-exporter}/bin/mysqld_exporter"
+        "--web.listen-address=${cfg.listenAddress}:${toString cfg.port}"
+        "--web.telemetry-path=${cfg.telemetryPath}"
+        (optionalString (cfg.configFile != null) ''--config.my-cnf=''${CREDENTIALS_DIRECTORY}/config'')
+        (escapeShellArgs cfg.extraFlags)
+      ];
+      RestrictAddressFamilies = [
+        # The exporter can be configured to talk to a local mysql server via a unix socket.
+        "AF_UNIX"
+      ];
+    };
+  };
+}
+

nixos/tests/prometheus-exporters.nix

@@ -716,6 +716,41 @@ let
       '';
     };
 
+    mysqld = {
+      exporterConfig = {
+        enable = true;
+        runAsLocalSuperUser = true;
+        configFile = pkgs.writeText "test-prometheus-exporter-mysqld-config.my-cnf" ''
+          [client]
+          user = exporter
+          password = snakeoilpassword
+        '';
+      };
+      metricProvider = {
+        services.mysql = {
+          enable = true;
+          package = pkgs.mariadb;
+          initialScript = pkgs.writeText "mysql-init-script.sql" ''
+            CREATE USER 'exporter'@'localhost'
+            IDENTIFIED BY 'snakeoilpassword'
+            WITH MAX_USER_CONNECTIONS 3;
+            GRANT PROCESS, REPLICATION CLIENT, SLAVE MONITOR, SELECT ON *.* TO 'exporter'@'localhost';
+          '';
+        };
+      };
+      exporterTest = ''
+        wait_for_unit("prometheus-mysqld-exporter.service")
+        wait_for_open_port(9104)
+        wait_for_unit("mysql.service")
+        succeed("curl -sSf http://localhost:9104/metrics | grep 'mysql_up 1'")
+        systemctl("stop mysql.service")
+        succeed("curl -sSf http://localhost:9104/metrics | grep 'mysql_up 0'")
+        systemctl("start mysql.service")
+        wait_for_unit("mysql.service")
+        succeed("curl -sSf http://localhost:9104/metrics | grep 'mysql_up 1'")
+      '';
+    };
+
     nextcloud = {
       exporterConfig = {
         enable = true;