Improve error message when overrides fail to parse (#5787)

* Improve error message when overrides fail to parse

* chlog

* better

Author: mapno

CHANGELOG.md

@@ -13,7 +13,8 @@
 * [ENHANCEMENT] Unsafe search hints for frontend performance tests [#5723](https://github.com/grafana/tempo/pull/5723) (@ruslan-mikhailov)
 * [ENHANCEMENT] Add new livestore alert to the tempo-mixin [#5752](https://github.com/grafana/tempo/pull/5752) (@javiermolinar)
 * [ENHANCEMENT] Improve shutdown time in the first 30 seconds [#5725](https://github.com/grafana/tempo/pull/5725) (@ldufr)
-* [ENHANCEMENT] Add metric for tracking added latency to write requests [#](https://github.com/grafana/tempo/pull/) (@mapno)
+* [ENHANCEMENT] Add metric for tracking added latency to write requests [#5781](https://github.com/grafana/tempo/pull/5781) (@mapno)
+* [ENHANCEMENT] Improve error message when overrides fail to parse [#5787](https://github.com/grafana/tempo/pull/5787) (@mapno)
 * [BUGFIX] Fix compactor to properly consider SSE-KMS information during metadata copy [#5774](https://github.com/grafana/tempo/pull/5774) (@steffsas)
 * [BUGFIX] Correctly track and reject too large traces in live stores. [#5757](https://github.com/grafana/tempo/pull/5757) (@joe-elliott)
 * [BUGFIX] Fix issues related to integer dedicated columns in vParquet5-preview2 [#5716](https://github.com/grafana/tempo/pull/5716) (@stoewer)

modules/overrides/config.go

@@ -249,8 +249,8 @@ func (c *Config) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	legacyCfg.PerTenantOverridePeriod = c.PerTenantOverridePeriod
 	legacyCfg.UserConfigurableOverridesConfig = c.UserConfigurableOverridesConfig
 
-	if err := unmarshal(&legacyCfg); err != nil {
-		return err
+	if legacyErr := unmarshal(&legacyCfg); legacyErr != nil {
+		return fmt.Errorf("failed to unmarshal config: %w; also failed in legacy format: %w", err, legacyErr)
 	}
 
 	c.Defaults = legacyCfg.DefaultOverrides.toNewLimits()