From 4d1a5423840774fe02fa6ff17199c8206ffb4879 Mon Sep 17 00:00:00 2001
From: arcnmx <git@git.arcn.mx>
Date: Thu, 30 May 2024 13:41:24 -0700
Subject: [PATCH] refactor(monitoring): static exporter discovery

---
 .../nixos/monitoring/ingest/prometheus.nix    | 43 +++++++----
 modules/system/exports/monitoring.nix         | 74 ++++++++++++++++++-
 2 files changed, 97 insertions(+), 20 deletions(-)

diff --git a/modules/nixos/monitoring/ingest/prometheus.nix b/modules/nixos/monitoring/ingest/prometheus.nix
index 6092433a..8a53b683 100644
--- a/modules/nixos/monitoring/ingest/prometheus.nix
+++ b/modules/nixos/monitoring/ingest/prometheus.nix
@@ -5,26 +5,37 @@
   ...
 }: let
   inherit (gensokyo-zone) systems;
-  inherit (lib.attrsets) filterAttrs mapAttrsToList;
+  inherit (lib.modules) mkDefault;
+  inherit (lib.attrsets) attrValues;
+  inherit (lib.lists) filter concatMap;
   nodeExporterSystems =
-    filterAttrs (
-      _: system:
+    filter (
+      system:
         system.config.access.online.enable &&
-        system.config.exports.services.prometheus-exporters-node.enable
+        system.config.exports.prometheus.exporter.services != [ ]
     )
-    systems;
+    (attrValues systems);
+  mkPortTarget = { system, service, portName }: let
+    port = service.ports.${portName};
+  in "${access.getAddressFor system.config.name "lan"}:${toString port.port}";
+  mkServiceConfig = system: serviceName: let
+    service = system.config.exports.services.${serviceName};
+    targets = map (portName: mkPortTarget {
+      inherit system service portName;
+    }) service.prometheus.exporter.ports;
+  in {
+    job_name = "${system.config.name}-${service.id}";
+    static_configs = [
+      {
+        inherit targets;
+        labels = mkDefault service.prometheus.exporter.labels;
+      }
+    ];
+  };
+  mapSystem = system: map (mkServiceConfig system) system.config.exports.prometheus.exporter.services;
 in {
   services.prometheus = {
-    port = 9090;
-    scrapeConfigs =
-      mapAttrsToList (_: system: {
-        job_name = "${system.config.name}-node-exporter";
-        static_configs = [ {
-          targets = [
-            "${access.getAddressFor system.config.name "local"}:${toString system.config.exports.services.prometheus-exporters-node.ports.default.port}"
-          ];
-        } ];
-      })
-      nodeExporterSystems;
+    port = mkDefault 9090;
+    scrapeConfigs = concatMap mapSystem nodeExporterSystems;
   };
 }
diff --git a/modules/system/exports/monitoring.nix b/modules/system/exports/monitoring.nix
index fd9cda5c..36620d00 100644
--- a/modules/system/exports/monitoring.nix
+++ b/modules/system/exports/monitoring.nix
@@ -1,11 +1,56 @@
-{
-  lib,
+let
+  portModule = {
+    lib,
+    ...
+  }: let
+    inherit (lib.options) mkEnableOption;
+  in {
+    options.prometheus = with lib.types; {
+      exporter.enable = mkEnableOption "prometheus metrics endpoint";
+    };
+  };
+  serviceModule = {
+    config,
+    lib,
+    ...
+  }: let
+    inherit (lib.options) mkOption;
+    inherit (lib.modules) mkOptionDefault;
+    inherit (lib.attrsets) attrNames filterAttrs;
+    exporterPorts = filterAttrs (_: port: port.enable && port.prometheus.exporter.enable) config.ports;
+  in {
+    options = with lib.types; {
+      prometheus = {
+        exporter = {
+          ports = mkOption {
+            type = listOf str;
+          };
+          labels = mkOption {
+            type = attrsOf str;
+            default = { };
+          };
+        };
+      };
+      ports = mkOption {
+        type = attrsOf (submoduleWith {
+          modules = [portModule];
+        });
+      };
+    };
+    config.prometheus = {
+      exporter.ports = mkOptionDefault (attrNames exporterPorts);
+    };
+  };
+in {
+  config,
   gensokyo-zone,
+  lib,
   ...
 }: let
   inherit (gensokyo-zone.lib) mapListToAttrs mapAlmostOptionDefaults mkAlmostOptionDefault;
-  inherit (lib.modules) mkIf;
-  inherit (lib.attrsets) nameValuePair;
+  inherit (lib.options) mkOption;
+  inherit (lib.modules) mkIf mkOptionDefault;
+  inherit (lib.attrsets) attrNames filterAttrs nameValuePair;
   mkExporter = { name, port }: nameValuePair "prometheus-exporters-${name}" ({config, ...}: {
     nixos = {
       serviceAttrPath = ["services" "prometheus" "exporters" name];
@@ -19,12 +64,31 @@
     ports.default = mapAlmostOptionDefaults {
       inherit port;
       protocol = "http";
+    } // {
+      prometheus.exporter.enable = true;
     };
   });
   exporters = mapListToAttrs mkExporter [
     { name = "node"; port = 9091; }
   ];
 in {
+  options.exports = with lib.types; {
+    prometheus = {
+      exporter.services = mkOption {
+        type = listOf str;
+      };
+    };
+    services = mkOption {
+      type = attrsOf (submoduleWith {
+        modules = [serviceModule];
+      });
+    };
+  };
+  config.exports.prometheus = let
+    exporterServices = filterAttrs (_: service: service.enable && service.prometheus.exporter.ports != [ ]) config.exports.services;
+  in {
+    exporter.services = mkOptionDefault (attrNames exporterServices);
+  };
   config.exports.services = {
     prometheus = {config, ...}: {
       id = mkAlmostOptionDefault "prometheus";
@@ -88,6 +152,8 @@ in {
       ports.default = mapAlmostOptionDefaults {
         port = 9094;
         protocol = "http";
+      } // {
+        prometheus.exporter.enable = true;
       };
     };
   } // exporters;