x-pack/metricbeat/module/gcp: Add omitted labels

CHANGELOG.next.asciidoc

@@ -168,6 +168,7 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 - Normalize AWS RDS CPU Utilization values before making the metadata API call. {pull}39664[39664]
 - Fix behavior of pagetypeinfo metrics {pull}39985[39985]
 - Fix query logic for temp and non-temp tablespaces in Oracle module. {issue}38051[38051] {pull}39787[39787]
+- Fix GCP omitted label-ECSCloud.ECSCloudInstance.ECSCloudInstanceID. {issue}40033[40033] {pull}40062[40062]
 
 *Osquerybeat*
 

x-pack/metricbeat/module/gcp/timeseries_metadata_collector.go

@@ -100,6 +100,13 @@ func (s *StackdriverTimeSeriesMetadataCollector) Metadata(ctx context.Context, i
 		// common.Mapstr seems to not work as expected when deleting keys so I have to iterate over all results to add
 		// the ones I want
 		for k, v := range s.timeSeries.Resource.Labels {
+
+			// We are omitting some labels here because they are added separately for services with additional metadata logic.
+			// However, we explicitly include the instance_id label to ensure it is not missed for services without additional metadata logic.
+			if k == TimeSeriesResponsePathForECSInstanceID {
+				_, _ = ecs.Put(ECSCloudInstanceIDKey, v)
+			}
+
 			if k == TimeSeriesResponsePathForECSAvailabilityZone || k == TimeSeriesResponsePathForECSInstanceID || k == TimeSeriesResponsePathForECSAccountID {
 				continue
 			}