Prometheus unbound exporter

[SuperSandro2000]

Motivation for this change

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[Ma27]

A VM test under nixos/tests/prometheus-exporters.nix would be appreciated as well :)

[WilliButz]

As @Ma27 already stated, a new exporter module should come with a VM test, validating at the very least the compatibility of module and package. To test the PR I wrote a small test case, feel free to apply the patch:

Basic VM Test

commit 2890a3dd15ae57865e7922f6dfd7f2e698cda3fd
Author: WilliButz <willibutz@posteo.de>
Date:   Tue Apr 27 18:00:55 2021 +0200

    nixos/tests/prometheus-exporters: add unbound test

diff --git a/nixos/tests/prometheus-exporters.nix b/nixos/tests/prometheus-exporters.nix
index 62c0080dd51..1afb49c9cf8 100644
--- a/nixos/tests/prometheus-exporters.nix
+++ b/nixos/tests/prometheus-exporters.nix
@@ -1000,6 +1000,29 @@ let
       '';
     };
 
+    unbound = {
+      exporterConfig = {
+        enable = true;
+        fetchType = "uds";
+        socketPath = "/run/unbound/unbound.ctl";
+      };
+      metricProvider = {
+        services.unbound = {
+          enable = true;
+          localControlSocketPath = "/run/unbound/unbound.ctl";
+        };
+        systemd.services.prometheus-unbound-exporter.serviceConfig = {
+          SupplementaryGroups = [ "unbound" ];
+        };
+      };
+      exporterTest = ''
+        wait_for_unit("unbound.service")
+        wait_for_unit("prometheus-unbound-exporter.service")
+        wait_for_open_port(9167)
+        succeed("curl -sSf localhost:9167/metrics | grep -q 'unbound_up 1'")
+      '';
+    };
+
     varnish = {
       exporterConfig = {
         enable = true;
diff --git a/pkgs/servers/monitoring/prometheus/unbound-exporter.nix b/pkgs/servers/monitoring/prometheus/unbound-exporter.nix
index c085226d909..fbe530ac22c 100644
--- a/pkgs/servers/monitoring/prometheus/unbound-exporter.nix
+++ b/pkgs/servers/monitoring/prometheus/unbound-exporter.nix
@@ -1,4 +1,4 @@
-{ lib, rustPlatform, fetchFromGitHub, openssl, pkg-config }:
+{ lib, rustPlatform, fetchFromGitHub, openssl, pkg-config, nixosTests }:
 
 rustPlatform.buildRustPackage rec {
   pname = "unbound-telemetry";
@@ -17,6 +17,8 @@ rustPlatform.buildRustPackage rec {
 
   buildInputs = [ openssl ];
 
+  passthru.tests = { inherit (nixosTests.prometheus-exporters) unbound; };
+
   meta = with lib; {
     description = "Prometheus exporter for Unbound DNS resolver";
     homepage = "https://github.com/svartalf/unbound-telemetry";