prometheus service: add

This is based on @benleys work: https://github.com/NixOS/nixpkgs/pull/8216
I updated changed the user and group ids.

nixos/modules/misc/ids.nix

@@ -275,6 +275,7 @@
       gocd-server = 252;
       terraria = 253;
       mattermost = 254;
+      prometheus = 255;
 
       # When adding a uid, make sure it doesn't match an existing gid. And don't use uids above 399!
 
@@ -520,6 +521,7 @@
       gocd-server = 252;
       terraria = 253;
       mattermost = 254;
+      prometheus = 255;
 
       # When adding a gid, make sure it doesn't match an existing
       # uid. Users and groups with the same name should have equal

nixos/modules/module-list.nix

@@ -286,6 +286,7 @@
   ./services/monitoring/monit.nix
   ./services/monitoring/munin.nix
   ./services/monitoring/nagios.nix
+  ./services/monitoring/prometheus.nix
   ./services/monitoring/riemann.nix
   ./services/monitoring/riemann-dash.nix
   ./services/monitoring/riemann-tools.nix

nixos/modules/services/monitoring/prometheus.nix

@@ -0,0 +1,418 @@
+{ config, pkgs, lib, ... }:
+
+with lib;
+
+let
+  cfg = config.services.prometheus;
+  promUser = "prometheus";
+  promGroup = "prometheus";
+
+  # Get a submodule without any embedded metadata:
+  _filter = x: filterAttrs (k: v: k != "_module") x;
+
+  # Pretty-print JSON to a file
+  writePrettyJSON = name: x:
+    pkgs.runCommand name { } ''
+      echo '${builtins.toJSON x}' | ${pkgs.jq}/bin/jq . > $out
+    '';
+
+  # This becomes the main config file
+  promConfig = {
+    global = cfg.globalConfig;
+    rule_files = cfg.ruleFiles ++ [
+      (pkgs.writeText "prometheus.rules" (concatStringsSep "\n" cfg.rules))
+    ];
+    scrape_configs = cfg.scrapeConfigs;
+  };
+
+  cmdlineArgs = cfg.extraFlags ++ [
+    "-storage.local.path=${cfg.dataDir}/metrics"
+    "-config.file=${writePrettyJSON "prometheus.yml" promConfig}"
+    "-web.listen-address=${cfg.listenAddress}"
+  ];
+
+  promTypes.globalConfig = types.submodule {
+    options = {
+      scrape_interval = mkOption {
+        type = types.str;
+        default = "1m";
+        description = ''
+          How frequently to scrape targets by default.
+        '';
+      };
+
+      scrape_timeout = mkOption {
+        type = types.str;
+        default = "10s";
+        description = ''
+          How long until a scrape request times out.
+        '';
+      };
+
+      evaluation_interval = mkOption {
+        type = types.str;
+        default = "1m";
+        description = ''
+          How frequently to evaluate rules by default.
+        '';
+      };
+
+      labels = mkOption {
+        type = types.attrsOf types.str;
+        default = {};
+        description = ''
+          The labels to add to any timeseries that this Prometheus instance
+          scrapes.
+        '';
+      };
+    };
+  };
+
+  promTypes.scrape_config = types.submodule {
+    options = {
+      job_name = mkOption {
+        type = types.str;
+        description = ''
+          The job name assigned to scraped metrics by default.
+        '';
+      };
+      scrape_interval = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = ''
+          How frequently to scrape targets from this job. Defaults to the
+          globally configured default.
+        '';
+      };
+      scrape_timeout = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = ''
+          Per-target timeout when scraping this job. Defaults to the
+          globally configured default.
+        '';
+      };
+      metrics_path = mkOption {
+        type = types.str;
+        default = "/metrics";
+        description = ''
+          The HTTP resource path on which to fetch metrics from targets.
+        '';
+      };
+      scheme = mkOption {
+        type = types.enum ["http" "https"];
+        default = "http";
+        description = ''
+          The URL scheme with which to fetch metrics from targets.
+        '';
+      };
+      basic_auth = mkOption {
+        type = types.nullOr (types.submodule {
+          options = {
+            username = mkOption {
+              type = types.str;
+              description = ''
+                HTTP username
+              '';
+            };
+            password = mkOption {
+              type = types.str;
+              description = ''
+                HTTP password
+              '';
+            };
+          };
+        });
+        default = null;
+        description = ''
+          Optional http login credentials for metrics scraping.
+        '';
+      };
+      dns_sd_configs = mkOption {
+        type = types.listOf promTypes.dns_sd_config;
+        default = [];
+        apply = x: map _filter x;
+        description = ''
+          List of DNS service discovery configurations.
+        '';
+      };
+      consul_sd_configs = mkOption {
+        type = types.listOf promTypes.consul_sd_config;
+        default = [];
+        apply = x: map _filter x;
+        description = ''
+          List of Consul service discovery configurations.
+        '';
+      };
+      file_sd_configs = mkOption {
+        type = types.listOf promTypes.file_sd_config;
+        default = [];
+        apply = x: map _filter x;
+        description = ''
+          List of file service discovery configurations.
+        '';
+      };
+      target_groups = mkOption {
+        type = types.listOf promTypes.target_group;
+        default = [];
+        apply = x: map _filter x;
+        description = ''
+          List of labeled target groups for this job.
+        '';
+      };
+      relabel_configs = mkOption {
+        type = types.listOf promTypes.relabel_config;
+        default = [];
+        apply = x: map _filter x;
+        description = ''
+          List of relabel configurations.
+        '';
+      };
+    };
+  };
+
+  promTypes.target_group = types.submodule {
+    options = {
+      targets = mkOption {
+        type = types.listOf types.str;
+        description = ''
+          The targets specified by the target group.
+        '';
+      };
+      labels = mkOption {
+        type = types.attrsOf types.str;
+        description = ''
+          Labels assigned to all metrics scraped from the targets.
+        '';
+      };
+    };
+  };
+
+  promTypes.dns_sd_config = types.submodule {
+    options = {
+      names = mkOption {
+        type = types.listOf types.str;
+        description = ''
+          A list of DNS SRV record names to be queried.
+        '';
+      };
+      refresh_interval = mkOption {
+        type = types.str;
+        default = "30s";
+        description = ''
+          The time after which the provided names are refreshed.
+        '';
+      };
+    };
+  };
+
+  promTypes.consul_sd_config = types.submodule {
+    options = {
+      server = mkOption {
+        type = types.str;
+        description = "Consul server to query.";
+      };
+      token = mkOption {
+        type = types.nullOr types.str;
+        description = "Consul token";
+      };
+      datacenter = mkOption {
+        type = types.nullOr types.str;
+        description = "Consul datacenter";
+      };
+      scheme = mkOption {
+        type = types.nullOr types.str;
+        description = "Consul scheme";
+      };
+      username = mkOption {
+        type = types.nullOr types.str;
+        description = "Consul username";
+      };
+      password = mkOption {
+        type = types.nullOr types.str;
+        description = "Consul password";
+      };
+
+      services = mkOption {
+        type = types.listOf types.str;
+        description = ''
+          A list of services for which targets are retrieved.
+        '';
+      };
+      tag_separator = mkOption {
+        type = types.str;
+        default = ",";
+        description = ''
+          The string by which Consul tags are joined into the tag label.
+        '';
+      };
+    };
+  };
+
+  promTypes.file_sd_config = types.submodule {
+    options = {
+      names = mkOption {
+        type = types.listOf types.str;
+        description = ''
+          Patterns for files from which target groups are extracted. Refer
+          to the Prometheus documentation for permitted filename patterns
+          and formats.
+
+        '';
+      };
+      refresh_interval = mkOption {
+        type = types.str;
+        default = "30s";
+        description = ''
+          Refresh interval to re-read the files.
+        '';
+      };
+    };
+  };
+
+  promTypes.relabel_config = types.submodule {
+    options = {
+      source_labels = mkOption {
+        type = types.listOf types.str;
+        description = ''
+          The source labels select values from existing labels. Their content
+          is concatenated using the configured separator and matched against
+          the configured regular expression.
+        '';
+      };
+      separator = mkOption {
+        type = types.str;
+        default = ";";
+        description = ''
+          Separator placed between concatenated source label values.
+        '';
+      };
+      target_label = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = ''
+          Label to which the resulting value is written in a replace action.
+          It is mandatory for replace actions.
+        '';
+      };
+      regex = mkOption {
+        type = types.str;
+        description = ''
+          Regular expression against which the extracted value is matched.
+        '';
+      };
+      replacement = mkOption {
+        type = types.str;
+        default = "";
+        description = ''
+          Replacement value against which a regex replace is performed if the
+          regular expression matches.
+        '';
+      };
+      action = mkOption {
+        type = types.enum ["replace" "keep" "drop"];
+        description = ''
+          Action to perform based on regex matching.
+        '';
+      };
+    };
+  };
+
+in {
+  options = {
+    services.prometheus = {
+
+      enable = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Enable the Prometheus monitoring daemon.
+        '';
+      };
+
+      listenAddress = mkOption {
+        type = types.str;
+        default = "0.0.0.0:9090";
+        description = ''
+          Address to listen on for the web interface, API, and telemetry.
+        '';
+      };
+
+      dataDir = mkOption {
+        type = types.path;
+        default = "/var/lib/prometheus";
+        description = ''
+          Directory to store Prometheus metrics data.
+        '';
+      };
+
+      extraFlags = mkOption {
+        type = types.listOf types.str;
+        default = [];
+        description = ''
+          Extra commandline options when launching Prometheus.
+        '';
+      };
+
+      globalConfig = mkOption {
+        type = promTypes.globalConfig;
+        default = {};
+        apply = _filter;
+        description = ''
+          Parameters that are valid in all  configuration contexts. They
+          also serve as defaults for other configuration sections
+        '';
+      };
+
+      rules = mkOption {
+        type = types.listOf types.str;
+        default = [];
+        description = ''
+          Alerting and/or Recording rules to evaluate at runtime.
+        '';
+      };
+
+      ruleFiles = mkOption {
+        type = types.listOf types.path;
+        default = [];
+        description = ''
+          Any additional rules files to include in this configuration.
+        '';
+      };
+
+      scrapeConfigs = mkOption {
+        type = types.listOf promTypes.scrape_config;
+        default = [];
+        apply = x: map _filter x;
+        description = ''
+          A list of scrape configurations.
+        '';
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    users.extraGroups.${promGroup}.gid = config.ids.gids.prometheus;
+    users.extraUsers.${promUser} = {
+      description = "Prometheus daemon user";
+      uid = config.ids.uids.prometheus;
+      group = promGroup;
+      home = cfg.dataDir;
+      createHome = true;
+    };
+    systemd.services.prometheus = {
+      wantedBy = [ "multi-user.target" ];
+      after    = [ "network.target" ];
+      script = ''
+        #!/bin/sh
+        exec ${pkgs.prometheus}/bin/prometheus \
+          ${concatStringsSep " \\\n  " cmdlineArgs}
+      '';
+      serviceConfig = {
+        User = promUser;
+        Restart  = "always";
+        WorkingDirectory = cfg.dataDir;
+      };
+    };
+  };
+}

nixos/tests/prometheus.nix

@@ -0,0 +1,29 @@
+import ./make-test.nix {
+  name = "prometheus";
+
+  nodes = {
+    one = { config, pkgs, ... }: {
+      services.prometheus = {
+        enable = true;
+        globalConfig = {
+          labels = { foo = "bar"; };
+        };
+        scrapeConfigs = [{
+          job_name = "prometheus";
+          target_groups = [{
+            targets = [ "127.0.0.1:9090" ];
+            labels = { instance = "localhost"; };
+          }];
+        }];
+        rules = [ ''testrule = count(up{job="prometheus"})'' ];
+      };
+    };
+  };
+
+  testScript = ''
+    startAll;
+    $one->waitForUnit("prometheus.service");
+    $one->waitForOpenPort(9090);
+    $one->succeed("curl -s http://127.0.0.1:9090/metrics");
+  '';
+}