Minor refactor for aggregation processor init (#15177) (#15186)

(cherry picked from commit 5b59aab)

Co-authored-by: Vishal Raj <[email protected]>

x-pack/apm-server/aggregation.go

@@ -11,9 +11,7 @@ import (
 	"github.com/elastic/apm-server/x-pack/apm-server/aggregation"
 )
 
-func newAggregationProcessors(args beater.ServerParams) ([]namedProcessor, error) {
-	var processors []namedProcessor
-
+func newAggregationProcessor(args beater.ServerParams) (namedProcessor, error) {
 	name := "LSM aggregator"
 	agg, err := aggregation.New(
 		args.Config.Aggregation.MaxServices,
@@ -24,9 +22,7 @@ func newAggregationProcessors(args beater.ServerParams) ([]namedProcessor, error
 		args.Logger,
 	)
 	if err != nil {
-		return nil, errors.Wrapf(err, "error creating %s", name)
+		return namedProcessor{}, errors.Wrapf(err, "error creating %s", name)
 	}
-	processors = append(processors, namedProcessor{name: name, processor: agg})
-
-	return processors, nil
+	return namedProcessor{name: name, processor: agg}, nil
 }

x-pack/apm-server/main.go

@@ -93,11 +93,11 @@ type processor interface {
 func newProcessors(args beater.ServerParams) ([]namedProcessor, error) {
 	var processors []namedProcessor
 
-	aggregationProcessors, err := newAggregationProcessors(args)
+	aggregationProcessor, err := newAggregationProcessor(args)
 	if err != nil {
 		return nil, err
 	}
-	processors = append(processors, aggregationProcessors...)
+	processors = append(processors, aggregationProcessor)
 
 	if args.Config.Sampling.Tail.Enabled {
 		const name = "tail sampler"