Add an option to configure the exporter buffer of the BatchProcessor (#5877)

resolve: https://github.com/open-telemetry/opentelemetry-go/issues/5238

---------

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>
Co-authored-by: Damien Mathieu <42@dmathieu.com>

CHANGELOG.md

@@ -11,6 +11,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 ### Added
 
 - Add `go.opentelemetry.io/otel/sdk/metric/exemplar` package which includes `Exemplar`, `Filter`, `TraceBasedFilter`, `AlwaysOnFilter`, `HistogramReservoir`, `FixedSizeReservoir`, `Reservoir`, `Value` and `ValueType` types. These will be used for configuring the exemplar reservoir for the metrics sdk. (#5747, #5862)
+- Add `WithExportBufferSize` option to log batch processor.(#5877)
 
 ### Changed
 

sdk/log/batch.go

@@ -19,6 +19,7 @@ const (
 	dfltExpInterval     = time.Second
 	dfltExpTimeout      = 30 * time.Second
 	dfltExpMaxBatchSize = 512
+	dfltExpBufferSize   = 1
 
 	envarMaxQSize        = "OTEL_BLRP_MAX_QUEUE_SIZE"
 	envarExpInterval     = "OTEL_BLRP_SCHEDULE_DELAY"
@@ -119,8 +120,7 @@ func NewBatchProcessor(exporter Exporter, opts ...BatchProcessorOption) *BatchPr
 	exporter = newChunkExporter(exporter, cfg.expMaxBatchSize.Value)
 
 	b := &BatchProcessor{
-		// TODO: explore making the size of this configurable.
-		exporter: newBufferExporter(exporter, 1),
+		exporter: newBufferExporter(exporter, cfg.expBufferSize.Value),
 
 		q:           newQueue(cfg.maxQSize.Value),
 		batchSize:   cfg.expMaxBatchSize.Value,
@@ -349,6 +349,7 @@ type batchConfig struct {
 	expInterval     setting[time.Duration]
 	expTimeout      setting[time.Duration]
 	expMaxBatchSize setting[int]
+	expBufferSize   setting[int]
 }
 
 func newBatchConfig(options []BatchProcessorOption) batchConfig {
@@ -382,6 +383,10 @@ func newBatchConfig(options []BatchProcessorOption) batchConfig {
 		clampMax[int](c.maxQSize.Value),
 		fallback[int](dfltExpMaxBatchSize),
 	)
+	c.expBufferSize = c.expBufferSize.Resolve(
+		clearLessThanOne[int](),
+		fallback[int](dfltExpBufferSize),
+	)
 
 	return c
 }
@@ -458,3 +463,15 @@ func WithExportMaxBatchSize(size int) BatchProcessorOption {
 		return cfg
 	})
 }
+
+// WithExportBufferSize sets the batch buffer size.
+// Batches will be temporarily kept in a memory buffer until they are exported.
+//
+// By default, a value of 1 will be used.
+// The default value is also used when the provided value is less than one.
+func WithExportBufferSize(size int) BatchProcessorOption {
+	return batchOptionFunc(func(cfg batchConfig) batchConfig {
+		cfg.expBufferSize = newSetting(size)
+		return cfg
+	})
+}

sdk/log/batch_test.go

@@ -70,6 +70,7 @@ func TestNewBatchConfig(t *testing.T) {
 				expInterval:     newSetting(dfltExpInterval),
 				expTimeout:      newSetting(dfltExpTimeout),
 				expMaxBatchSize: newSetting(dfltExpMaxBatchSize),
+				expBufferSize:   newSetting(dfltExpBufferSize),
 			},
 		},
 		{
@@ -79,12 +80,14 @@ func TestNewBatchConfig(t *testing.T) {
 				WithExportInterval(time.Microsecond),
 				WithExportTimeout(time.Hour),
 				WithExportMaxBatchSize(2),
+				WithExportBufferSize(3),
 			},
 			want: batchConfig{
 				maxQSize:        newSetting(10),
 				expInterval:     newSetting(time.Microsecond),
 				expTimeout:      newSetting(time.Hour),
 				expMaxBatchSize: newSetting(2),
+				expBufferSize:   newSetting(3),
 			},
 		},
 		{
@@ -100,6 +103,7 @@ func TestNewBatchConfig(t *testing.T) {
 				expInterval:     newSetting(100 * time.Millisecond),
 				expTimeout:      newSetting(1000 * time.Millisecond),
 				expMaxBatchSize: newSetting(1),
+				expBufferSize:   newSetting(dfltExpBufferSize),
 			},
 		},
 		{
@@ -109,12 +113,14 @@ func TestNewBatchConfig(t *testing.T) {
 				WithExportInterval(-1 * time.Microsecond),
 				WithExportTimeout(-1 * time.Hour),
 				WithExportMaxBatchSize(-2),
+				WithExportBufferSize(-2),
 			},
 			want: batchConfig{
 				maxQSize:        newSetting(dfltMaxQSize),
 				expInterval:     newSetting(dfltExpInterval),
 				expTimeout:      newSetting(dfltExpTimeout),
 				expMaxBatchSize: newSetting(dfltExpMaxBatchSize),
+				expBufferSize:   newSetting(dfltExpBufferSize),
 			},
 		},
 		{
@@ -130,6 +136,7 @@ func TestNewBatchConfig(t *testing.T) {
 				expInterval:     newSetting(dfltExpInterval),
 				expTimeout:      newSetting(dfltExpTimeout),
 				expMaxBatchSize: newSetting(dfltExpMaxBatchSize),
+				expBufferSize:   newSetting(dfltExpBufferSize),
 			},
 		},
 		{
@@ -146,12 +153,14 @@ func TestNewBatchConfig(t *testing.T) {
 				WithExportInterval(time.Microsecond),
 				WithExportTimeout(time.Hour),
 				WithExportMaxBatchSize(2),
+				WithExportBufferSize(2),
 			},
 			want: batchConfig{
 				maxQSize:        newSetting(3),
 				expInterval:     newSetting(time.Microsecond),
 				expTimeout:      newSetting(time.Hour),
 				expMaxBatchSize: newSetting(2),
+				expBufferSize:   newSetting(2),
 			},
 		},
 		{
@@ -159,12 +168,14 @@ func TestNewBatchConfig(t *testing.T) {
 			options: []BatchProcessorOption{
 				WithMaxQueueSize(1),
 				WithExportMaxBatchSize(10),
+				WithExportBufferSize(3),
 			},
 			want: batchConfig{
 				maxQSize:        newSetting(1),
 				expInterval:     newSetting(dfltExpInterval),
 				expTimeout:      newSetting(dfltExpTimeout),
 				expMaxBatchSize: newSetting(1),
+				expBufferSize:   newSetting(3),
 			},
 		},
 	}