[exporterhelper] Replace experimental converter interface with functi…

…on (#8764)

As proposed in
#8122 (comment)

If we need backward conversion, we will use an optional argument to the
helper function instead of an optional interface.

.chloggen/dmitryax_use-func-instead-of-converter-interface.yaml

@@ -0,0 +1,20 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: breaking
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: exporterhelper
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Replace converter interface with function in the new experimental exporter helper.
+
+# One or more tracking issues or pull requests related to the change
+issues: [8122]
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

exporter/exporterhelper/constants.go

@@ -18,10 +18,10 @@ var (
 	errNilPushMetricsData = errors.New("nil PushMetrics")
 	// errNilPushLogsData is returned when a nil PushLogs is given.
 	errNilPushLogsData = errors.New("nil PushLogs")
-	// errNilTracesConverter is returned when a nil TracesConverter is given.
-	errNilTracesConverter = errors.New("nil TracesConverter")
-	// errNilMetricsConverter is returned when a nil MetricsConverter is given.
-	errNilMetricsConverter = errors.New("nil MetricsConverter")
-	// errNilLogsConverter is returned when a nil LogsConverter is given.
-	errNilLogsConverter = errors.New("nil LogsConverter")
+	// errNilTracesConverter is returned when a nil RequestFromTracesFunc is given.
+	errNilTracesConverter = errors.New("nil RequestFromTracesFunc")
+	// errNilMetricsConverter is returned when a nil RequestFromMetricsFunc is given.
+	errNilMetricsConverter = errors.New("nil RequestFromMetricsFunc")
+	// errNilLogsConverter is returned when a nil RequestFromLogsFunc is given.
+	errNilLogsConverter = errors.New("nil RequestFromLogsFunc")
 )

exporter/exporterhelper/logs.go

@@ -108,21 +108,18 @@ func NewLogsExporter(
 	}, err
 }
 
-// LogsConverter provides an interface for converting plog.Logs into a request.
+// RequestFromLogsFunc converts plog.Logs data into a user-defined request.
 // This API is at the early stage of development and may change without backward compatibility
 // until https://github.com/open-telemetry/opentelemetry-collector/issues/8122 is resolved.
-type LogsConverter interface {
-	// RequestFromLogs converts plog.Logs data into a request.
-	RequestFromLogs(context.Context, plog.Logs) (Request, error)
-}
+type RequestFromLogsFunc func(context.Context, plog.Logs) (Request, error)
 
 // NewLogsRequestExporter creates new logs exporter based on custom LogsConverter and RequestSender.
 // This API is at the early stage of development and may change without backward compatibility
 // until https://github.com/open-telemetry/opentelemetry-collector/issues/8122 is resolved.
 func NewLogsRequestExporter(
 	_ context.Context,
 	set exporter.CreateSettings,
-	converter LogsConverter,
+	converter RequestFromLogsFunc,
 	options ...Option,
 ) (exporter.Logs, error) {
 	if set.Logger == nil {
@@ -139,7 +136,7 @@ func NewLogsRequestExporter(
 	}
 
 	lc, err := consumer.NewLogs(func(ctx context.Context, ld plog.Logs) error {
-		req, cErr := converter.RequestFromLogs(ctx, ld)
+		req, cErr := converter(ctx, ld)
 		if cErr != nil {
 			set.Logger.Error("Failed to convert logs. Dropping data.",
 				zap.Int("dropped_log_records", ld.LogRecordCount()),

exporter/exporterhelper/logs_test.go

@@ -65,7 +65,7 @@ func TestLogsExporter_NilLogger(t *testing.T) {
 }
 
 func TestLogsRequestExporter_NilLogger(t *testing.T) {
-	le, err := NewLogsRequestExporter(context.Background(), exporter.CreateSettings{}, &fakeRequestConverter{})
+	le, err := NewLogsRequestExporter(context.Background(), exporter.CreateSettings{}, (&fakeRequestConverter{}).requestFromLogsFunc)
 	require.Nil(t, le)
 	require.Equal(t, errNilLogger, err)
 }
@@ -96,7 +96,8 @@ func TestLogsExporter_Default(t *testing.T) {
 
 func TestLogsRequestExporter_Default(t *testing.T) {
 	ld := plog.NewLogs()
-	le, err := NewLogsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(), &fakeRequestConverter{})
+	le, err := NewLogsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(),
+		(&fakeRequestConverter{}).requestFromLogsFunc)
 	assert.NotNil(t, le)
 	assert.NoError(t, err)
 
@@ -117,7 +118,8 @@ func TestLogsExporter_WithCapabilities(t *testing.T) {
 
 func TestLogsRequestExporter_WithCapabilities(t *testing.T) {
 	capabilities := consumer.Capabilities{MutatesData: true}
-	le, err := NewLogsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(), &fakeRequestConverter{}, WithCapabilities(capabilities))
+	le, err := NewLogsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(),
+		(&fakeRequestConverter{}).requestFromLogsFunc, WithCapabilities(capabilities))
 	require.NoError(t, err)
 	require.NotNil(t, le)
 
@@ -136,7 +138,8 @@ func TestLogsExporter_Default_ReturnError(t *testing.T) {
 func TestLogsRequestExporter_Default_ConvertError(t *testing.T) {
 	ld := plog.NewLogs()
 	want := errors.New("convert_error")
-	le, err := NewLogsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(), &fakeRequestConverter{logsError: want})
+	le, err := NewLogsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(),
+		(&fakeRequestConverter{logsError: want}).requestFromLogsFunc)
 	require.NoError(t, err)
 	require.NotNil(t, le)
 	require.Equal(t, consumererror.NewPermanent(want), le.ConsumeLogs(context.Background(), ld))
@@ -146,7 +149,7 @@ func TestLogsRequestExporter_Default_ExportError(t *testing.T) {
 	ld := plog.NewLogs()
 	want := errors.New("export_error")
 	le, err := NewLogsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(),
-		&fakeRequestConverter{requestError: want})
+		(&fakeRequestConverter{requestError: want}).requestFromLogsFunc)
 	require.NoError(t, err)
 	require.NotNil(t, le)
 	require.Equal(t, want, le.ConsumeLogs(context.Background(), ld))
@@ -193,7 +196,9 @@ func TestLogsRequestExporter_WithRecordMetrics(t *testing.T) {
 	require.NoError(t, err)
 	t.Cleanup(func() { require.NoError(t, tt.Shutdown(context.Background())) })
 
-	le, err := NewLogsRequestExporter(context.Background(), exporter.CreateSettings{ID: fakeLogsExporterName, TelemetrySettings: tt.TelemetrySettings, BuildInfo: component.NewDefaultBuildInfo()}, &fakeRequestConverter{})
+	le, err := NewLogsRequestExporter(context.Background(),
+		exporter.CreateSettings{ID: fakeLogsExporterName, TelemetrySettings: tt.TelemetrySettings, BuildInfo: component.NewDefaultBuildInfo()},
+		(&fakeRequestConverter{}).requestFromLogsFunc)
 	require.NoError(t, err)
 	require.NotNil(t, le)
 
@@ -220,7 +225,7 @@ func TestLogsRequestExporter_WithRecordMetrics_ExportError(t *testing.T) {
 	t.Cleanup(func() { require.NoError(t, tt.Shutdown(context.Background())) })
 
 	le, err := NewLogsRequestExporter(context.Background(), exporter.CreateSettings{ID: fakeLogsExporterName, TelemetrySettings: tt.TelemetrySettings, BuildInfo: component.NewDefaultBuildInfo()},
-		&fakeRequestConverter{requestError: want})
+		(&fakeRequestConverter{requestError: want}).requestFromLogsFunc)
 	require.Nil(t, err)
 	require.NotNil(t, le)
 
@@ -272,7 +277,7 @@ func TestLogsRequestExporter_WithSpan(t *testing.T) {
 	otel.SetTracerProvider(set.TracerProvider)
 	defer otel.SetTracerProvider(nooptrace.NewTracerProvider())
 
-	le, err := NewLogsRequestExporter(context.Background(), set, &fakeRequestConverter{})
+	le, err := NewLogsRequestExporter(context.Background(), set, (&fakeRequestConverter{}).requestFromLogsFunc)
 	require.Nil(t, err)
 	require.NotNil(t, le)
 	checkWrapSpanForLogsExporter(t, sr, set.TracerProvider.Tracer("test"), le, nil, 1)
@@ -300,7 +305,7 @@ func TestLogsRequestExporter_WithSpan_ReturnError(t *testing.T) {
 	defer otel.SetTracerProvider(nooptrace.NewTracerProvider())
 
 	want := errors.New("my_error")
-	le, err := NewLogsRequestExporter(context.Background(), set, &fakeRequestConverter{requestError: want})
+	le, err := NewLogsRequestExporter(context.Background(), set, (&fakeRequestConverter{requestError: want}).requestFromLogsFunc)
 	require.Nil(t, err)
 	require.NotNil(t, le)
 	checkWrapSpanForLogsExporter(t, sr, set.TracerProvider.Tracer("test"), le, want, 1)
@@ -322,7 +327,8 @@ func TestLogsRequestExporter_WithShutdown(t *testing.T) {
 	shutdownCalled := false
 	shutdown := func(context.Context) error { shutdownCalled = true; return nil }
 
-	le, err := NewLogsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(), &fakeRequestConverter{}, WithShutdown(shutdown))
+	le, err := NewLogsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(),
+		(&fakeRequestConverter{}).requestFromLogsFunc, WithShutdown(shutdown))
 	assert.NotNil(t, le)
 	assert.NoError(t, err)
 
@@ -345,7 +351,8 @@ func TestLogsRequestExporter_WithShutdown_ReturnError(t *testing.T) {
 	want := errors.New("my_error")
 	shutdownErr := func(context.Context) error { return want }
 
-	le, err := NewLogsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(), &fakeRequestConverter{}, WithShutdown(shutdownErr))
+	le, err := NewLogsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(),
+		(&fakeRequestConverter{}).requestFromLogsFunc, WithShutdown(shutdownErr))
 	assert.NotNil(t, le)
 	assert.NoError(t, err)
 

exporter/exporterhelper/metrics.go

@@ -108,21 +108,18 @@ func NewMetricsExporter(
 	}, err
 }
 
-// MetricsConverter provides an interface for converting pmetric.Metrics into a request.
+// RequestFromMetricsFunc converts pdata.Metrics into a user-defined request.
 // This API is at the early stage of development and may change without backward compatibility
 // until https://github.com/open-telemetry/opentelemetry-collector/issues/8122 is resolved.
-type MetricsConverter interface {
-	// RequestFromMetrics converts pdata.Metrics into a request.
-	RequestFromMetrics(context.Context, pmetric.Metrics) (Request, error)
-}
+type RequestFromMetricsFunc func(context.Context, pmetric.Metrics) (Request, error)
 
 // NewMetricsRequestExporter creates a new metrics exporter based on a custom MetricsConverter and RequestSender.
 // This API is at the early stage of development and may change without backward compatibility
 // until https://github.com/open-telemetry/opentelemetry-collector/issues/8122 is resolved.
 func NewMetricsRequestExporter(
 	_ context.Context,
 	set exporter.CreateSettings,
-	converter MetricsConverter,
+	converter RequestFromMetricsFunc,
 	options ...Option,
 ) (exporter.Metrics, error) {
 	if set.Logger == nil {
@@ -139,7 +136,7 @@ func NewMetricsRequestExporter(
 	}
 
 	mc, err := consumer.NewMetrics(func(ctx context.Context, md pmetric.Metrics) error {
-		req, cErr := converter.RequestFromMetrics(ctx, md)
+		req, cErr := converter(ctx, md)
 		if cErr != nil {
 			set.Logger.Error("Failed to convert metrics. Dropping data.",
 				zap.Int("dropped_data_points", md.DataPointCount()),

exporter/exporterhelper/metrics_test.go

@@ -65,7 +65,8 @@ func TestMetricsExporter_NilLogger(t *testing.T) {
 }
 
 func TestMetricsRequestExporter_NilLogger(t *testing.T) {
-	me, err := NewMetricsRequestExporter(context.Background(), exporter.CreateSettings{}, fakeRequestConverter{})
+	me, err := NewMetricsRequestExporter(context.Background(), exporter.CreateSettings{},
+		(&fakeRequestConverter{}).requestFromMetricsFunc)
 	require.Nil(t, me)
 	require.Equal(t, errNilLogger, err)
 }
@@ -96,7 +97,8 @@ func TestMetricsExporter_Default(t *testing.T) {
 
 func TestMetricsRequestExporter_Default(t *testing.T) {
 	md := pmetric.NewMetrics()
-	me, err := NewMetricsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(), fakeRequestConverter{})
+	me, err := NewMetricsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(),
+		(&fakeRequestConverter{}).requestFromMetricsFunc)
 	assert.NoError(t, err)
 	assert.NotNil(t, me)
 
@@ -117,8 +119,8 @@ func TestMetricsExporter_WithCapabilities(t *testing.T) {
 
 func TestMetricsRequestExporter_WithCapabilities(t *testing.T) {
 	capabilities := consumer.Capabilities{MutatesData: true}
-	me, err := NewMetricsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(), fakeRequestConverter{},
-		WithCapabilities(capabilities))
+	me, err := NewMetricsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(),
+		(&fakeRequestConverter{}).requestFromMetricsFunc, WithCapabilities(capabilities))
 	assert.NoError(t, err)
 	assert.NotNil(t, me)
 
@@ -137,7 +139,8 @@ func TestMetricsExporter_Default_ReturnError(t *testing.T) {
 func TestMetricsRequestExporter_Default_ConvertError(t *testing.T) {
 	md := pmetric.NewMetrics()
 	want := errors.New("convert_error")
-	me, err := NewMetricsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(), fakeRequestConverter{metricsError: want})
+	me, err := NewMetricsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(),
+		(&fakeRequestConverter{metricsError: want}).requestFromMetricsFunc)
 	require.NoError(t, err)
 	require.NotNil(t, me)
 	require.Equal(t, consumererror.NewPermanent(want), me.ConsumeMetrics(context.Background(), md))
@@ -147,7 +150,7 @@ func TestMetricsRequestExporter_Default_ExportError(t *testing.T) {
 	md := pmetric.NewMetrics()
 	want := errors.New("export_error")
 	me, err := NewMetricsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(),
-		fakeRequestConverter{requestError: want})
+		(&fakeRequestConverter{requestError: want}).requestFromMetricsFunc)
 	require.NoError(t, err)
 	require.NotNil(t, me)
 	require.Equal(t, want, me.ConsumeMetrics(context.Background(), md))
@@ -194,7 +197,9 @@ func TestMetricsRequestExporter_WithRecordMetrics(t *testing.T) {
 	require.NoError(t, err)
 	t.Cleanup(func() { require.NoError(t, tt.Shutdown(context.Background())) })
 
-	me, err := NewMetricsRequestExporter(context.Background(), exporter.CreateSettings{ID: fakeMetricsExporterName, TelemetrySettings: tt.TelemetrySettings, BuildInfo: component.NewDefaultBuildInfo()}, fakeRequestConverter{})
+	me, err := NewMetricsRequestExporter(context.Background(),
+		exporter.CreateSettings{ID: fakeMetricsExporterName, TelemetrySettings: tt.TelemetrySettings, BuildInfo: component.NewDefaultBuildInfo()},
+		(&fakeRequestConverter{}).requestFromMetricsFunc)
 	require.NoError(t, err)
 	require.NotNil(t, me)
 
@@ -220,7 +225,9 @@ func TestMetricsRequestExporter_WithRecordMetrics_ExportError(t *testing.T) {
 	require.NoError(t, err)
 	t.Cleanup(func() { require.NoError(t, tt.Shutdown(context.Background())) })
 
-	me, err := NewMetricsRequestExporter(context.Background(), exporter.CreateSettings{ID: fakeMetricsExporterName, TelemetrySettings: tt.TelemetrySettings, BuildInfo: component.NewDefaultBuildInfo()}, fakeRequestConverter{requestError: want})
+	me, err := NewMetricsRequestExporter(context.Background(),
+		exporter.CreateSettings{ID: fakeMetricsExporterName, TelemetrySettings: tt.TelemetrySettings, BuildInfo: component.NewDefaultBuildInfo()},
+		(&fakeRequestConverter{requestError: want}).requestFromMetricsFunc)
 	require.NoError(t, err)
 	require.NotNil(t, me)
 
@@ -272,7 +279,7 @@ func TestMetricsRequestExporter_WithSpan(t *testing.T) {
 	otel.SetTracerProvider(set.TracerProvider)
 	defer otel.SetTracerProvider(nooptrace.NewTracerProvider())
 
-	me, err := NewMetricsRequestExporter(context.Background(), set, fakeRequestConverter{})
+	me, err := NewMetricsRequestExporter(context.Background(), set, (&fakeRequestConverter{}).requestFromMetricsFunc)
 	require.NoError(t, err)
 	require.NotNil(t, me)
 	checkWrapSpanForMetricsExporter(t, sr, set.TracerProvider.Tracer("test"), me, nil, 2)
@@ -300,7 +307,7 @@ func TestMetricsRequestExporter_WithSpan_ExportError(t *testing.T) {
 	defer otel.SetTracerProvider(nooptrace.NewTracerProvider())
 
 	want := errors.New("my_error")
-	me, err := NewMetricsRequestExporter(context.Background(), set, fakeRequestConverter{requestError: want})
+	me, err := NewMetricsRequestExporter(context.Background(), set, (&fakeRequestConverter{requestError: want}).requestFromMetricsFunc)
 	require.NoError(t, err)
 	require.NotNil(t, me)
 	checkWrapSpanForMetricsExporter(t, sr, set.TracerProvider.Tracer("test"), me, want, 2)
@@ -324,7 +331,7 @@ func TestMetricsRequestExporter_WithShutdown(t *testing.T) {
 	shutdown := func(context.Context) error { shutdownCalled = true; return nil }
 
 	me, err := NewMetricsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(),
-		&fakeRequestConverter{}, WithShutdown(shutdown))
+		(&fakeRequestConverter{}).requestFromMetricsFunc, WithShutdown(shutdown))
 	assert.NotNil(t, me)
 	assert.NoError(t, err)
 
@@ -350,7 +357,7 @@ func TestMetricsRequestExporter_WithShutdown_ReturnError(t *testing.T) {
 	shutdownErr := func(context.Context) error { return want }
 
 	me, err := NewMetricsRequestExporter(context.Background(), exportertest.NewNopCreateSettings(),
-		&fakeRequestConverter{}, WithShutdown(shutdownErr))
+		(&fakeRequestConverter{}).requestFromMetricsFunc, WithShutdown(shutdownErr))
 	assert.NotNil(t, me)
 	assert.NoError(t, err)
 

exporter/exporterhelper/request_test.go

@@ -31,14 +31,14 @@ type fakeRequestConverter struct {
 	requestError error
 }
 
-func (c fakeRequestConverter) RequestFromMetrics(_ context.Context, md pmetric.Metrics) (Request, error) {
-	return fakeRequest{items: md.DataPointCount(), err: c.requestError}, c.metricsError
+func (frc *fakeRequestConverter) requestFromMetricsFunc(_ context.Context, md pmetric.Metrics) (Request, error) {
+	return fakeRequest{items: md.DataPointCount(), err: frc.requestError}, frc.metricsError
 }
 
-func (c fakeRequestConverter) RequestFromTraces(_ context.Context, td ptrace.Traces) (Request, error) {
-	return fakeRequest{items: td.SpanCount(), err: c.requestError}, c.tracesError
+func (frc *fakeRequestConverter) requestFromTracesFunc(_ context.Context, md ptrace.Traces) (Request, error) {
+	return fakeRequest{items: md.SpanCount(), err: frc.requestError}, frc.tracesError
 }
 
-func (c fakeRequestConverter) RequestFromLogs(_ context.Context, ld plog.Logs) (Request, error) {
-	return fakeRequest{items: ld.LogRecordCount(), err: c.requestError}, c.logsError
+func (frc *fakeRequestConverter) requestFromLogsFunc(_ context.Context, md plog.Logs) (Request, error) {
+	return fakeRequest{items: md.LogRecordCount(), err: frc.requestError}, frc.logsError
 }

exporter/exporterhelper/traces.go

@@ -108,21 +108,18 @@ func NewTracesExporter(
 	}, err
 }
 
-// TracesConverter provides an interface for converting ptrace.Traces into a request.
+// RequestFromTracesFunc converts ptrace.Traces into a user-defined Request.
 // This API is at the early stage of development and may change without backward compatibility
 // until https://github.com/open-telemetry/opentelemetry-collector/issues/8122 is resolved.
-type TracesConverter interface {
-	// RequestFromTraces converts ptrace.Traces into a Request.
-	RequestFromTraces(context.Context, ptrace.Traces) (Request, error)
-}
+type RequestFromTracesFunc func(context.Context, ptrace.Traces) (Request, error)
 
 // NewTracesRequestExporter creates a new traces exporter based on a custom TracesConverter and RequestSender.
 // This API is at the early stage of development and may change without backward compatibility
 // until https://github.com/open-telemetry/opentelemetry-collector/issues/8122 is resolved.
 func NewTracesRequestExporter(
 	_ context.Context,
 	set exporter.CreateSettings,
-	converter TracesConverter,
+	converter RequestFromTracesFunc,
 	options ...Option,
 ) (exporter.Traces, error) {
 	if set.Logger == nil {
@@ -139,7 +136,7 @@ func NewTracesRequestExporter(
 	}
 
 	tc, err := consumer.NewTraces(func(ctx context.Context, td ptrace.Traces) error {
-		req, cErr := converter.RequestFromTraces(ctx, td)
+		req, cErr := converter(ctx, td)
 		if cErr != nil {
 			set.Logger.Error("Failed to convert traces. Dropping data.",
 				zap.Int("dropped_spans", td.SpanCount()),