From 75c5a703ab06d9267cd3aa8938c9e4b0706a9125 Mon Sep 17 00:00:00 2001
From: Maximilian Bosch <maximilian@mbosch.me>
Date: Mon, 3 May 2021 17:01:13 +0200
Subject: [PATCH] prometheus-knot-exporter: add patch to fix stats

This is a patch I filed against upstream[1] a while ago. As it isn't
merged yet and fixes configurations with all stats enabled in knot
(otherwise it'd crash when sending a request to `localhost:9433`), I
decided that it makes sense to add it to the package directly.

I extended the test to make sure that it only passes with this patch.

[1] https://github.com/ghedo/knot_exporter/pull/6
---
 nixos/tests/prometheus-exporters.nix          | 37 ++++++++++++++++++-
 .../monitoring/prometheus/knot-exporter.nix   | 11 +++++-
 2 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/nixos/tests/prometheus-exporters.nix b/nixos/tests/prometheus-exporters.nix
index 21419c0d081..2b17d0ff78f 100644
--- a/nixos/tests/prometheus-exporters.nix
+++ b/nixos/tests/prometheus-exporters.nix
@@ -334,13 +334,48 @@ let
         services.knot = {
           enable = true;
           extraArgs = [ "-v" ];
+          extraConfig = ''
+            server:
+              listen: 127.0.0.1@53
+
+            template:
+              - id: default
+                global-module: mod-stats
+                dnssec-signing: off
+                zonefile-sync: -1
+                journal-db: /var/lib/knot/journal
+                kasp-db: /var/lib/knot/kasp
+                timer-db: /var/lib/knot/timer
+                zonefile-load: difference
+                storage: ${pkgs.buildEnv {
+                  name = "foo";
+                  paths = [
+                    (pkgs.writeTextDir "test.zone" ''
+                      @ SOA ns.example.com. noc.example.com. 2019031301 86400 7200 3600000 172800
+                      @       NS      ns1
+                      @       NS      ns2
+                      ns1     A       192.168.0.1
+                    '')
+                  ];
+                }}
+
+            mod-stats:
+              - id: custom
+                edns-presence: on
+                query-type: on
+
+            zone:
+              - domain: test
+                file: test.zone
+                module: mod-stats/custom
+          '';
         };
       };
       exporterTest = ''
         wait_for_unit("knot.service")
         wait_for_unit("prometheus-knot-exporter.service")
         wait_for_open_port(9433)
-        succeed("curl -sSf 'localhost:9433' | grep -q 'knot_server_zone_count 0.0'")
+        succeed("curl -sSf 'localhost:9433' | grep -q 'knot_server_zone_count 1.0'")
       '';
     };
 
diff --git a/pkgs/servers/monitoring/prometheus/knot-exporter.nix b/pkgs/servers/monitoring/prometheus/knot-exporter.nix
index 9d99685b569..42b6047d3d4 100644
--- a/pkgs/servers/monitoring/prometheus/knot-exporter.nix
+++ b/pkgs/servers/monitoring/prometheus/knot-exporter.nix
@@ -1,4 +1,4 @@
-{ stdenv, fetchFromGitHub, lib, python3, nixosTests }:
+{ stdenv, fetchFromGitHub, lib, python3, nixosTests, fetchpatch }:
 
 stdenv.mkDerivation rec {
   pname = "knot-exporter";
@@ -11,6 +11,15 @@ stdenv.mkDerivation rec {
     sha256 = "sha256-4au4lpaq3jcqC2JXdCcf8h+YN8Nmm4eE0kZwA+1rWlc=";
   };
 
+  patches = [
+    # Fixes a crash with all metrics enabled. See
+    # https://github.com/ghedo/knot_exporter/pull/6 for further context.
+    (fetchpatch {
+      url = "https://github.com/ghedo/knot_exporter/commit/2317476e080369450ae51a707ccd30d4b89d680f.patch";
+      sha256 = "sha256-yEPu8EE1V/draNx9DeMrPj+bMfJRxauweo33dITl4AA=";
+    })
+  ];
+
   dontBuild = true;
 
   nativeBuildInputs = [ python3.pkgs.wrapPython ];