nixos/prometheus-sql-exporter: new module

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

@@ -44,6 +44,7 @@ let
     "redis"
     "rspamd"
     "snmp"
+    "sql"
     "surfboard"
     "tor"
     "unifi"
@@ -217,6 +218,14 @@ in
         Please specify either 'services.prometheus.exporters.mail.configuration'
           or 'services.prometheus.exporters.mail.configFile'.
       '';
+    } {
+      assertion = cfg.sql.enable -> (
+        (cfg.sql.configFile == null) != (cfg.sql.configuration == null)
+      );
+      message = ''
+        Please specify either 'services.prometheus.exporters.sql.configuration' or
+          'services.prometheus.exporters.sql.configFile'
+      '';
     } ];
   }] ++ [(mkIf config.services.minio.enable {
     services.prometheus.exporters.minio.minioAddress  = mkDefault "http://localhost:9000";

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

@@ -0,0 +1,104 @@
+{ config, lib, pkgs, options }:
+with lib;
+let
+  cfg = config.services.prometheus.exporters.sql;
+  cfgOptions = {
+    options = with types; {
+      jobs = mkOption {
+        type = attrsOf (submodule jobOptions);
+        default = { };
+        description = "An attrset of metrics scraping jobs to run.";
+      };
+    };
+  };
+  jobOptions = {
+    options = with types; {
+      interval = mkOption {
+        type = str;
+        description = ''
+          How often to run this job, specified in
+          <link xlink:href="https://golang.org/pkg/time/#ParseDuration">Go duration</link> format.
+        '';
+      };
+      connections = mkOption {
+        type = listOf str;
+        description = "A list of connection strings of the SQL servers to scrape metrics from";
+      };
+      startupSql = mkOption {
+        type = listOf str;
+        default = [];
+        description = "A list of SQL statements to execute once after making a connection.";
+      };
+      queries = mkOption {
+        type = attrsOf (submodule queryOptions);
+        description = "SQL queries to run.";
+      };
+    };
+  };
+  queryOptions = {
+    options = with types; {
+      help = mkOption {
+        type = nullOr str;
+        default = null;
+        description = "A human-readable description of this metric.";
+      };
+      labels = mkOption {
+        type = listOf str;
+        default = [ ];
+        description = "A set of columns that will be used as Prometheus labels.";
+      };
+      query = mkOption {
+        type = str;
+        description = "The SQL query to run.";
+      };
+      values = mkOption {
+        type = listOf str;
+        description = "A set of columns that will be used as values of this metric.";
+      };
+    };
+  };
+
+  configFile =
+    if cfg.configFile != null
+    then cfg.configFile
+    else
+      let
+        nameInline = mapAttrsToList (k: v: v // { name = k; });
+        renameStartupSql = j: removeAttrs (j // { startup_sql = j.startupSql; }) [ "startupSql" ];
+        configuration = {
+          jobs = map renameStartupSql
+            (nameInline (mapAttrs (k: v: (v // { queries = nameInline v.queries; })) cfg.configuration.jobs));
+        };
+      in
+      builtins.toFile "config.yaml" (builtins.toJSON configuration);
+in
+{
+  extraOpts = {
+    configFile = mkOption {
+      type = with types; nullOr path;
+      default = null;
+      description = ''
+        Path to configuration file.
+      '';
+    };
+    configuration = mkOption {
+      type = with types; nullOr (submodule cfgOptions);
+      default = null;
+      description = ''
+        Exporter configuration as nix attribute set. Mutually exclusive with 'configFile' option.
+      '';
+    };
+  };
+
+  port = 9237;
+  serviceOpts = {
+    serviceConfig = {
+      ExecStart = ''
+        ${pkgs.prometheus-sql-exporter}/bin/sql_exporter \
+          -web.listen-address ${cfg.listenAddress}:${toString cfg.port} \
+          -config.file ${configFile} \
+          ${concatStringsSep " \\\n  " cfg.extraFlags}
+      '';
+    };
+  };
+}

nixos/tests/prometheus-exporters.nix

@@ -578,6 +578,50 @@ let
       '';
     };
 
+    sql = {
+      exporterConfig = {
+        configuration.jobs.points = {
+          interval = "1m";
+          connections = [
+            "postgres://prometheus-sql-exporter@/data?host=/run/postgresql&sslmode=disable"
+          ];
+          queries = {
+            points = {
+              labels = [ "name" ];
+              help = "Amount of points accumulated per person";
+              values = [ "amount" ];
+              query = "SELECT SUM(amount) as amount, name FROM points GROUP BY name";
+            };
+          };
+        };
+        enable = true;
+        user = "postgres";
+      };
+      metricProvider = {
+        services.postgresql = {
+          enable = true;
+          initialScript = builtins.toFile "init.sql" ''
+            CREATE DATABASE data;
+            \c data;
+            CREATE TABLE points (amount INT, name TEXT);
+            INSERT INTO points(amount, name) VALUES (1, 'jack');
+            INSERT INTO points(amount, name) VALUES (2, 'jill');
+            INSERT INTO points(amount, name) VALUES (3, 'jack');
+
+            CREATE USER "prometheus-sql-exporter";
+            GRANT ALL PRIVILEGES ON DATABASE data TO "prometheus-sql-exporter";
+            GRANT SELECT ON points TO "prometheus-sql-exporter";
+          '';
+        };
+        systemd.services.prometheus-sql-exporter.after = [ "postgresql.service" ];
+      };
+      exporterTest = ''
+        wait_for_unit("prometheus-sql-exporter.service")
+        wait_for_open_port(9237)
+        succeed("curl http://localhost:9237/metrics | grep -c 'sql_points{' | grep -q 2")
+      '';
+    };
+
     surfboard = {
       exporterConfig = {
         enable = true;