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nixos/prometheus: check configuration before starting service

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With `promtool` we can check the validity of a configuration before
deploying it. This avoids situations where you would end up with a
broken monitoring system without noticing it - since the monitoring
broke down. :-)
This commit is contained in:
Andreas Rammhold 2018-11-04 14:30:47 +01:00 committed by Robin Gloster
parent 0de150e0f2
commit 6795bdd58c
1 changed files with 13 additions and 5 deletions
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18
nixos/modules/services/monitoring/prometheus/default.nix
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@ -10,6 +10,13 @@ let
# Get a submodule without any embedded metadata: # Get a submodule without any embedded metadata:
_filter = x: filterAttrs (k: v: k != "_module") x; _filter = x: filterAttrs (k: v: k != "_module") x;
# a wrapper that verifies that the configuration is valid
promtoolCheck = what: name: file: pkgs.runCommand "${name}-${what}-checked"
{ buildInputs = [ cfg.package ]; } ''
ln -s ${file} $out
promtool ${what} $out
'';
# Pretty-print JSON to a file # Pretty-print JSON to a file
writePrettyJSON = name: x: writePrettyJSON = name: x:
pkgs.runCommand name { } '' pkgs.runCommand name { } ''
@ -19,18 +26,19 @@ let
# This becomes the main config file # This becomes the main config file
promConfig = { promConfig = {
global = cfg.globalConfig; global = cfg.globalConfig;
rule_files = cfg.ruleFiles ++ [ rule_files = map (promtoolCheck "check-rules" "rules") (cfg.ruleFiles ++ [
(pkgs.writeText "prometheus.rules" (concatStringsSep "\n" cfg.rules)) (pkgs.writeText "prometheus.rules" (concatStringsSep "\n" cfg.rules))
]; ]);
scrape_configs = cfg.scrapeConfigs; scrape_configs = cfg.scrapeConfigs;
}; };
generatedPrometheusYml = writePrettyJSON "prometheus.yml" promConfig; generatedPrometheusYml = writePrettyJSON "prometheus.yml" promConfig;
prometheusYml = prometheusYml = let
if cfg.configText != null then yml = if cfg.configText != null then
pkgs.writeText "prometheus.yml" cfg.configText pkgs.writeText "prometheus.yml" cfg.configText
else generatedPrometheusYml; else generatedPrometheusYml;
in promtoolCheck "check-config" "prometheus.yml" yml;
cmdlineArgs = cfg.extraFlags ++ [ cmdlineArgs = cfg.extraFlags ++ [
"-storage.local.path=${cfg.dataDir}/metrics" "-storage.local.path=${cfg.dataDir}/metrics"