[chore][exporter/elasticsearch] Add benchmark for logs consumer (#33035)

**Description:** <Describe what has changed.> Add a benchmark for
elasticsearch exporter's `LogsConsumer`.

**Link to tracking Issue:** <Issue number if applicable>
[32504](#32504)

**Testing:** <Describe what testing was performed and which tests were
added.> `cd exporter/elasticsearchexporter/integrationtest && go test
-bench=BenchmarkLogsExporter -run=^$ ./...`

**Documentation:** <Describe the documentation added.> N/A

exporter/elasticsearchexporter/integrationtest/datareceiver.go

@@ -33,7 +33,7 @@ type esDataReceiver struct {
 	endpoint string
 }
 
-func newElasticsearchDataReceiver(t testing.TB) testbed.DataReceiver {
+func newElasticsearchDataReceiver(t testing.TB) *esDataReceiver {
 	return &esDataReceiver{
 		DataReceiverBase: testbed.DataReceiverBase{},
 		endpoint:         fmt.Sprintf("http://%s:%d", testbed.DefaultHost, testutil.GetAvailablePort(t)),
@@ -113,6 +113,11 @@ type mockESReceiver struct {
 }
 
 func newMockESReceiver(params receiver.CreateSettings, cfg *config, next consumer.Logs) (receiver.Logs, error) {
+	emptyLogs := plog.NewLogs()
+	emptyLogs.ResourceLogs().AppendEmpty().
+		ScopeLogs().AppendEmpty().
+		LogRecords().AppendEmpty()
+
 	r := mux.NewRouter()
 	r.Use(func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -129,13 +134,10 @@ func newMockESReceiver(params receiver.CreateSettings, cfg *config, next consume
 			for k, item := range itemMap {
 				// Ideally bulk request should be converted to log record
 				// however, since we only assert count for now there is no
-				// need to do the actual translation.
-				logs := plog.NewLogs()
-				logs.ResourceLogs().AppendEmpty().
-					ScopeLogs().AppendEmpty().
-					LogRecords().AppendEmpty()
-
-				if err := next.ConsumeLogs(context.Background(), logs); err != nil {
+				// need to do the actual translation. We use a pre-initialized
+				// empty plog.Logs to reduce allocation impact on tests and
+				// benchmarks due to this.
+				if err := next.ConsumeLogs(context.Background(), emptyLogs); err != nil {
 					response.HasErrors = true
 					item.Status = http.StatusTooManyRequests
 					item.Error.Type = "simulated_es_error"

exporter/elasticsearchexporter/integrationtest/exporter_bench_test.go

@@ -0,0 +1,80 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package integrationtest
+
+import (
+	"context"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/consumer"
+	"go.opentelemetry.io/collector/exporter/exportertest"
+	"go.opentelemetry.io/collector/pdata/plog"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/exporter/elasticsearchexporter"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/testbed/testbed"
+)
+
+func BenchmarkLogsExporter(b *testing.B) {
+	for _, tc := range []struct {
+		name      string
+		batchSize int
+	}{
+		{name: "small_batch", batchSize: 10},
+		{name: "medium_batch", batchSize: 100},
+		{name: "large_batch", batchSize: 1000},
+		{name: "xlarge_batch", batchSize: 10000},
+	} {
+		b.Run(tc.name, func(b *testing.B) {
+			benchmarkLogs(b, tc.batchSize)
+		})
+	}
+}
+
+func benchmarkLogs(b *testing.B, batchSize int) {
+	var generatedCount, observedCount atomic.Uint64
+
+	receiver := newElasticsearchDataReceiver(b)
+	factory := elasticsearchexporter.NewFactory()
+
+	cfg := factory.CreateDefaultConfig().(*elasticsearchexporter.Config)
+	cfg.Endpoints = []string{receiver.endpoint}
+	cfg.Flush.Interval = 10 * time.Millisecond
+	cfg.NumWorkers = 1
+
+	exporter, err := factory.CreateLogsExporter(
+		context.Background(),
+		exportertest.NewNopCreateSettings(),
+		cfg,
+	)
+	require.NoError(b, err)
+
+	provider := testbed.NewPerfTestDataProvider(testbed.LoadOptions{ItemsPerBatch: batchSize})
+	provider.SetLoadGeneratorCounters(&generatedCount)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	logsConsumer, err := consumer.NewLogs(func(_ context.Context, ld plog.Logs) error {
+		observedCount.Add(uint64(ld.LogRecordCount()))
+		return nil
+	})
+	require.NoError(b, err)
+
+	require.NoError(b, receiver.Start(nil, nil, logsConsumer))
+	defer func() { require.NoError(b, receiver.Stop()) }()
+
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		b.StopTimer()
+		logs, _ := provider.GenerateLogs()
+		b.StartTimer()
+		require.NoError(b, exporter.ConsumeLogs(ctx, logs))
+	}
+	require.NoError(b, exporter.Shutdown(ctx))
+	require.Equal(b, generatedCount.Load(), observedCount.Load(), "failed to send all logs to backend")
+}