nixos/prometheus-snmp-exporter: add config check

This is introduced and enabled by default because the config syntax for
the exporter changed with release 0.23.0.

This should make the breaking config change obvious before services are
deployed with an incompatible old config.

The check is based on the check present in the blackbox-exporter module.
This commit is contained in:
WilliButz 2024-01-12 18:42:37 +01:00
parent a8ea9fe492
commit bb9c7762bc
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2 changed files with 40 additions and 3 deletions

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@ -124,6 +124,10 @@ The pre-existing [services.ankisyncd](#opt-services.ankisyncd.enable) has been m
- `security.pam.enableSSHAgentAuth` now requires `services.openssh.authorizedKeysFiles` to be non-empty,
which is the case when `services.openssh.enable` is true. Previously, `pam_ssh_agent_auth` silently failed to work.
- The configuration format for `services.prometheus.exporters.snmp` changed with release 0.23.0.
The module now includes an optional config check, that is enabled by default, to make the change obvious before any deployment.
More information about the configuration syntax change is available in the [upstream repository](https://github.com/prometheus/snmp_exporter/blob/b75fc6b839ee3f3ccbee68bee55f1ae99555084a/auth-split-migration.md).
## Other Notable Changes {#sec-release-24.05-notable-changes}
<!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->

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@ -4,6 +4,25 @@ with lib;
let
cfg = config.services.prometheus.exporters.snmp;
# This ensures that we can deal with string paths, path types and
# store-path strings with context.
coerceConfigFile = file:
if (builtins.isPath file) || (lib.isStorePath file) then
file
else
(lib.warn ''
${logPrefix}: configuration file "${file}" is being copied to the nix-store.
If you would like to avoid that, please set enableConfigCheck to false.
'' /. + file);
checkConfig = file:
pkgs.runCommandLocal "checked-snmp-exporter-config.yml" {
nativeBuildInputs = [ pkgs.buildPackages.prometheus-snmp-exporter ];
} ''
ln -s ${coerceConfigFile file} $out
snmp_exporter --dry-run --config.file $out
'';
in
{
port = 9116;
@ -31,6 +50,16 @@ in
};
};
enableConfigCheck = mkOption {
type = types.bool;
default = true;
description = lib.mdDoc ''
Whether to run a correctness check for the configuration file. This depends
on the configuration file residing in the nix-store. Paths passed as string will
be copied to the store.
'';
};
logFormat = mkOption {
type = types.enum ["logfmt" "json"];
default = "logfmt";
@ -48,9 +77,13 @@ in
};
};
serviceOpts = let
configFile = if cfg.configurationPath != null
then cfg.configurationPath
else "${pkgs.writeText "snmp-exporter-conf.yml" (builtins.toJSON cfg.configuration)}";
uncheckedConfigFile = if cfg.configurationPath != null
then cfg.configurationPath
else "${pkgs.writeText "snmp-exporter-conf.yml" (builtins.toJSON cfg.configuration)}";
configFile = if cfg.enableConfigCheck then
checkConfig uncheckedConfigFile
else
uncheckedConfigFile;
in {
serviceConfig = {
ExecStart = ''