[chore] add receiver adapter benchmark tests (open-telemetry#35833)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

This PR introduces a benchmark test for the receiver adapter which tests
the performance of handling the log entries sent to the `LogEmitter`,
which are then received and converted by the receiver adapter. The
changes have been made based on the comment linked here:
open-telemetry#35669 (comment)

<!-- Issue number (e.g. #1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Part of open-telemetry#35453

<!--Describe what testing was performed and which tests were added.-->
#### Testing

Added additional benchmark tests

---------

Signed-off-by: Florian Bacher <[email protected]>

Author: bacherfl

pkg/stanza/adapter/receiver_test.go

@@ -16,7 +16,10 @@ import (
 	"github.com/stretchr/testify/require"
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/component/componenttest"
+	"go.opentelemetry.io/collector/consumer"
 	"go.opentelemetry.io/collector/consumer/consumertest"
+	"go.opentelemetry.io/collector/pdata/plog"
+	"go.opentelemetry.io/collector/receiver/receiverhelper"
 	"go.opentelemetry.io/collector/receiver/receivertest"
 	"gopkg.in/yaml.v2"
 
@@ -164,6 +167,102 @@ func TestShutdownFlush(t *testing.T) {
 	)
 }
 
+func BenchmarkReceiver(b *testing.B) {
+	b.Run(
+		"1 Log entry per iteration",
+		func(b *testing.B) {
+			benchmarkReceiver(b, 1)
+		},
+	)
+	b.Run(
+		"10 Log entries per iteration",
+		func(b *testing.B) {
+			benchmarkReceiver(b, 10)
+		},
+	)
+	b.Run(
+		"100 Log entries per iteration",
+		func(b *testing.B) {
+			benchmarkReceiver(b, 100)
+		},
+	)
+	b.Run(
+		"1_000 Log entries per iteration",
+		func(b *testing.B) {
+			benchmarkReceiver(b, 1_000)
+		},
+	)
+	b.Run(
+		"10_000 Log entries per iteration",
+		func(b *testing.B) {
+			benchmarkReceiver(b, 10_000)
+		},
+	)
+}
+
+func benchmarkReceiver(b *testing.B, logsPerIteration int) {
+	iterationComplete := make(chan struct{})
+	nextIteration := make(chan struct{})
+
+	inputBuilder := &testInputBuilder{
+		numberOfLogEntries: logsPerIteration,
+		nextIteration:      nextIteration,
+	}
+	inputCfg := operator.Config{
+		Builder: inputBuilder,
+	}
+
+	set := componenttest.NewNopTelemetrySettings()
+	emitter := helper.NewLogEmitter(set)
+	defer func() {
+		require.NoError(b, emitter.Stop())
+	}()
+
+	pipe, err := pipeline.Config{
+		Operators:     []operator.Config{inputCfg},
+		DefaultOutput: emitter,
+	}.Build(set)
+	require.NoError(b, err)
+
+	storageClient := storagetest.NewInMemoryClient(
+		component.KindReceiver,
+		component.MustNewID("foolog"),
+		"test",
+	)
+
+	converter := NewConverter(set)
+
+	obsrecv, err := receiverhelper.NewObsReport(receiverhelper.ObsReportSettings{ReceiverCreateSettings: receivertest.NewNopSettings()})
+	require.NoError(b, err)
+
+	mockConsumer := &testConsumer{
+		receivedAllLogs: iterationComplete,
+		expectedLogs:    uint32(logsPerIteration),
+		receivedLogs:    atomic.Uint32{},
+	}
+	rcv := &receiver{
+		set:           set,
+		pipe:          pipe,
+		emitter:       emitter,
+		consumer:      mockConsumer,
+		converter:     converter,
+		obsrecv:       obsrecv,
+		storageClient: storageClient,
+	}
+
+	b.ResetTimer()
+
+	require.NoError(b, rcv.Start(context.Background(), nil))
+
+	for i := 0; i < b.N; i++ {
+		nextIteration <- struct{}{}
+		<-iterationComplete
+		mockConsumer.receivedLogs.Store(0)
+	}
+
+	require.NoError(b, rcv.Shutdown(context.Background()))
+}
+
 func BenchmarkReadLine(b *testing.B) {
 	filePath := filepath.Join(b.TempDir(), "bench.log")
 
@@ -281,3 +380,94 @@ func BenchmarkParseAndMap(b *testing.B) {
 		}
 	}
 }
+
+const testInputOperatorTypeStr = "test_input"
+
+type testInputBuilder struct {
+	numberOfLogEntries int
+	nextIteration      chan struct{}
+}
+
+func (t *testInputBuilder) ID() string {
+	return testInputOperatorTypeStr
+}
+
+func (t *testInputBuilder) Type() string {
+	return testInputOperatorTypeStr
+}
+
+func (t *testInputBuilder) Build(settings component.TelemetrySettings) (operator.Operator, error) {
+	inputConfig := helper.NewInputConfig(t.ID(), testInputOperatorTypeStr)
+	inputOperator, err := inputConfig.Build(settings)
+	if err != nil {
+		return nil, err
+	}
+
+	return &testInputOperator{
+		InputOperator:      inputOperator,
+		numberOfLogEntries: t.numberOfLogEntries,
+		nextIteration:      t.nextIteration,
+	}, nil
+}
+
+func (t *testInputBuilder) SetID(_ string) {}
+
+var _ operator.Operator = &testInputOperator{}
+
+type testInputOperator struct {
+	helper.InputOperator
+	numberOfLogEntries int
+	nextIteration      chan struct{}
+	cancelFunc         context.CancelFunc
+}
+
+func (t *testInputOperator) ID() string {
+	return testInputOperatorTypeStr
+}
+
+func (t *testInputOperator) Type() string {
+	return testInputOperatorTypeStr
+}
+
+func (t *testInputOperator) Start(_ operator.Persister) error {
+	ctx, cancelFunc := context.WithCancel(context.Background())
+	t.cancelFunc = cancelFunc
+
+	e := complexEntry()
+	go func() {
+		for {
+			select {
+			case <-t.nextIteration:
+				for i := 0; i < t.numberOfLogEntries; i++ {
+					_ = t.Write(context.Background(), e)
+				}
+			case <-ctx.Done():
+				return
+			}
+		}
+
+	}()
+	return nil
+}
+
+func (t *testInputOperator) Stop() error {
+	t.cancelFunc()
+	return nil
+}
+
+type testConsumer struct {
+	receivedAllLogs chan struct{}
+	expectedLogs    uint32
+	receivedLogs    atomic.Uint32
+}
+
+func (t *testConsumer) Capabilities() consumer.Capabilities {
+	return consumer.Capabilities{}
+}
+
+func (t *testConsumer) ConsumeLogs(_ context.Context, ld plog.Logs) error {
+	if t.receivedLogs.Add(uint32(ld.LogRecordCount())) >= t.expectedLogs {
+		t.receivedAllLogs <- struct{}{}
+	}
+	return nil
+}