From 0a5bba0f15bea325bf5d316da979b126e645da67 Mon Sep 17 00:00:00 2001
From: Bouke van der Bijl <i@bou.ke>
Date: Mon, 24 Mar 2025 11:27:15 +0100
Subject: [PATCH] nixos/opentelemetry-collector: validate config

---
 .../manual/release-notes/rl-2511.section.md   |  2 +
 .../monitoring/opentelemetry-collector.nix    | 56 +++++++++++--------
 2 files changed, 36 insertions(+), 22 deletions(-)

diff --git a/nixos/doc/manual/release-notes/rl-2511.section.md b/nixos/doc/manual/release-notes/rl-2511.section.md
index 848fa1eb9b52..8dc6829d7182 100644
--- a/nixos/doc/manual/release-notes/rl-2511.section.md
+++ b/nixos/doc/manual/release-notes/rl-2511.section.md
@@ -435,3 +435,5 @@
 - The `open-webui` package's postgres support have been moved to optional dependencies to comply with upstream changes in 0.6.26.
 
 - `prl-tools` has been moved out of `linuxPackages` because Parallels Guest Tools become driverless since 26.1.0.
+
+- `services.opentelemetry-collector` has a new option `validateConfigFile` option that checks the configuration file during build. It is enabled by default if the configuration file is in the Nix store.
diff --git a/nixos/modules/services/monitoring/opentelemetry-collector.nix b/nixos/modules/services/monitoring/opentelemetry-collector.nix
index 125dec00b6cf..a722c7a88b5f 100644
--- a/nixos/modules/services/monitoring/opentelemetry-collector.nix
+++ b/nixos/modules/services/monitoring/opentelemetry-collector.nix
@@ -13,12 +13,27 @@ let
     mkOption
     types
     getExe
+    isStorePath
+    literalMD
     ;
 
   cfg = config.services.opentelemetry-collector;
   opentelemetry-collector = cfg.package;
 
   settingsFormat = pkgs.formats.yaml { };
+  generatedConf =
+    if cfg.configFile == null then
+      settingsFormat.generate "config.yaml" cfg.settings
+    else
+      cfg.configFile;
+  conf =
+    if cfg.validateConfigFile then
+      pkgs.runCommandLocal "config.yaml" { inherit generatedConf; } ''
+        cp $generatedConf $out
+        ${getExe opentelemetry-collector} validate --config=file:$out
+      ''
+    else
+      generatedConf;
 in
 {
   options.services.opentelemetry-collector = {
@@ -43,6 +58,11 @@ in
         Specify a path to a configuration file that Opentelemetry Collector should use.
       '';
     };
+
+    validateConfigFile = lib.mkEnableOption "Validate configuration file" // {
+      defaultText = literalMD "`true` if `configFile` is a store path";
+      default = isStorePath cfg.configFile;
+    };
   };
 
   config = mkIf cfg.enable {
@@ -61,28 +81,20 @@ in
       description = "Opentelemetry Collector Service Daemon";
       wantedBy = [ "multi-user.target" ];
 
-      serviceConfig =
-        let
-          conf =
-            if cfg.configFile == null then
-              settingsFormat.generate "config.yaml" cfg.settings
-            else
-              cfg.configFile;
-        in
-        {
-          ExecStart = "${getExe opentelemetry-collector} --config=file:${conf}";
-          DynamicUser = true;
-          Restart = "always";
-          ProtectSystem = "full";
-          DevicePolicy = "closed";
-          NoNewPrivileges = true;
-          WorkingDirectory = "%S/opentelemetry-collector";
-          StateDirectory = "opentelemetry-collector";
-          SupplementaryGroups = [
-            # allow to read the systemd journal for opentelemetry-collector
-            "systemd-journal"
-          ];
-        };
+      serviceConfig = {
+        ExecStart = "${getExe opentelemetry-collector} --config=file:${conf}";
+        DynamicUser = true;
+        Restart = "always";
+        ProtectSystem = "full";
+        DevicePolicy = "closed";
+        NoNewPrivileges = true;
+        WorkingDirectory = "%S/opentelemetry-collector";
+        StateDirectory = "opentelemetry-collector";
+        SupplementaryGroups = [
+          # allow to read the systemd journal for opentelemetry-collector
+          "systemd-journal"
+        ];
+      };
     };
   };
 }