refactor: remove unused apm tracer (#17658)

apm tracer field is not used, remove it since
we are moving to otel anyway

Author: kruskall

internal/beater/beater.go

@@ -892,7 +892,7 @@ func (s *Runner) newLibbeatFinalBatchProcessor(
 		return nil, nil, fmt.Errorf("failed to create libbeat output pipeline: %w", err)
 	}
 	pipelineConnector := pipetool.WithACKer(pipeline, acker)
-	publisher, err := publish.NewPublisher(pipelineConnector, tracer)
+	publisher, err := publish.NewPublisher(pipelineConnector)
 	if err != nil {
 		return nil, nil, err
 	}

internal/publish/pub.go

@@ -25,7 +25,6 @@ import (
 	"time"
 
 	"github.com/pkg/errors"
-	"go.elastic.co/apm/v2"
 	"go.elastic.co/fastjson"
 
 	"github.com/elastic/beats/v7/libbeat/beat"
@@ -47,7 +46,6 @@ type Reporter func(context.Context, PendingReq) error
 // concurrent HTTP requests trying to publish at the same time is limited.
 type Publisher struct {
 	stopped chan struct{}
-	tracer  *apm.Tracer
 	client  beat.Client
 
 	mu              sync.RWMutex
@@ -73,10 +71,9 @@ var (
 //
 // GOMAXPROCS goroutines are started for forwarding events to libbeat.
 // Stop must be called to close the beat.Client and free resources.
-func NewPublisher(pipeline beat.Pipeline, tracer *apm.Tracer) (*Publisher, error) {
+func NewPublisher(pipeline beat.Pipeline) (*Publisher, error) {
 	processingCfg := beat.ProcessingConfig{}
 	p := &Publisher{
-		tracer:  tracer,
 		stopped: make(chan struct{}),
 
 		// One request will be actively processed by the

internal/publish/pub_test.go

@@ -31,7 +31,6 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
-	"go.elastic.co/apm/v2/apmtest"
 	"go.elastic.co/fastjson"
 
 	"github.com/elastic/beats/v7/libbeat/beat"
@@ -54,7 +53,7 @@ func TestPublisherStop(t *testing.T) {
 	// Create a pipeline with a limited queue size and no outputs,
 	// so we can simulate a pipeline that blocks indefinitely.
 	pipeline, client := newBlockingPipeline(t)
-	publisher, err := publish.NewPublisher(pipeline, apmtest.DiscardTracer)
+	publisher, err := publish.NewPublisher(pipeline)
 	require.NoError(t, err)
 	defer func() {
 		cancelledContext, cancel := context.WithCancel(context.Background())
@@ -90,7 +89,7 @@ func TestPublisherStop(t *testing.T) {
 
 func TestPublisherStopShutdownInactive(t *testing.T) {
 	pipeline, _ := newBlockingPipeline(t)
-	publisher, err := publish.NewPublisher(pipeline, apmtest.DiscardTracer)
+	publisher, err := publish.NewPublisher(pipeline)
 	require.NoError(t, err)
 
 	// There are no active events, so the publisher should stop immediately
@@ -192,7 +191,6 @@ func BenchmarkPublisher(b *testing.B) {
 	acker.Open()
 	publisher, err := publish.NewPublisher(
 		pipetool.WithACKer(pipeline, acker),
-		apmtest.DiscardTracer,
 	)
 	require.NoError(b, err)