[chore] Deprecate the interface exporter.Request.Merge() (#12012)

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

This PR removes the interface `exporter.Request.Merge()` because
`Merge()` is just a special case of `MergeSplit()`.
With just one interface, we no longer need an if-else loop in the
batcher based on MaxConfigSize. `MergeSplit()` should be able to handle
both the case where MaxConfigSize is specified or the case where it is
not

<!-- Issue number if applicable -->
#### Link to tracking issue
Fixes #

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

All the existing cases should still pass.

<!--Describe the documentation added.-->
#### Documentation

<!--Please delete paragraphs that you did not use before submitting.-->

Author: sfc-gh-sili

exporter/exporterhelper/internal/batch_sender.go

@@ -202,12 +202,12 @@ func (bs *BatchSender) sendMergeBatch(ctx context.Context, req internal.Request)
 	bs.mu.Lock()
 
 	if bs.activeBatch.request != nil {
-		var err error
-		req, err = bs.activeBatch.request.Merge(ctx, req)
+		res, err := bs.activeBatch.request.MergeSplit(ctx, bs.cfg.MaxSizeConfig, req)
 		if err != nil {
 			bs.mu.Unlock()
 			return err
 		}
+		req = res[0]
 	}
 
 	bs.activeRequests.Add(1)

exporter/exporterhelper/internal/request.go

@@ -56,35 +56,25 @@ func (r *fakeRequest) ItemsCount() int {
 	return r.items
 }
 
-func (r *fakeRequest) Merge(_ context.Context,
-	r2 internal.Request,
-) (internal.Request, error) {
-	if r == nil {
-		return r2, nil
-	}
-	fr2 := r2.(*fakeRequest)
-	if fr2.mergeErr != nil {
-		return nil, fr2.mergeErr
-	}
-	return &fakeRequest{
-		items:     r.items + fr2.items,
-		sink:      r.sink,
-		exportErr: fr2.exportErr,
-		delay:     r.delay + fr2.delay,
-	}, nil
-}
-
-func (r *fakeRequest) MergeSplit(ctx context.Context, cfg exporterbatcher.MaxSizeConfig,
-	r2 internal.Request,
-) ([]internal.Request, error) {
+func (r *fakeRequest) MergeSplit(_ context.Context, cfg exporterbatcher.MaxSizeConfig, r2 internal.Request) ([]internal.Request, error) {
 	if r.mergeErr != nil {
 		return nil, r.mergeErr
 	}
 
 	maxItems := cfg.MaxSizeItems
 	if maxItems == 0 {
-		r, err := r.Merge(ctx, r2)
-		return []internal.Request{r}, err
+		fr2 := r2.(*fakeRequest)
+		if fr2.mergeErr != nil {
+			return nil, fr2.mergeErr
+		}
+		return []internal.Request{
+			&fakeRequest{
+				items:     r.items + fr2.items,
+				sink:      r.sink,
+				exportErr: fr2.exportErr,
+				delay:     r.delay + fr2.delay,
+			},
+		}, nil
 	}
 
 	var fr2 *fakeRequest

exporter/exporterhelper/internal/retry_sender_test.go

@@ -418,10 +418,6 @@ func (mer *mockErrorRequest) ItemsCount() int {
 	return 7
 }
 
-func (mer *mockErrorRequest) Merge(context.Context, internal.Request) (internal.Request, error) {
-	return nil, nil
-}
-
 func (mer *mockErrorRequest) MergeSplit(context.Context, exporterbatcher.MaxSizeConfig, internal.Request) ([]internal.Request, error) {
 	return nil, nil
 }
@@ -468,10 +464,6 @@ func (m *mockRequest) ItemsCount() int {
 	return m.cnt
 }
 
-func (m *mockRequest) Merge(context.Context, internal.Request) (internal.Request, error) {
-	return nil, nil
-}
-
 func (m *mockRequest) MergeSplit(context.Context, exporterbatcher.MaxSizeConfig, internal.Request) ([]internal.Request, error) {
 	return nil, nil
 }

exporter/exporterhelper/logs_batch.go

@@ -11,16 +11,6 @@ import (
 	"go.opentelemetry.io/collector/pdata/plog"
 )
 
-// Merge merges the provided logs request into the current request and returns the merged request.
-func (req *logsRequest) Merge(_ context.Context, r2 Request) (Request, error) {
-	lr2, ok2 := r2.(*logsRequest)
-	if !ok2 {
-		return nil, errors.New("invalid input type")
-	}
-	lr2.ld.ResourceLogs().MoveAndAppendTo(req.ld.ResourceLogs())
-	return req, nil
-}
-
 // MergeSplit splits and/or merges the provided logs request and the current request into one or more requests
 // conforming with the MaxSizeConfig.
 func (req *logsRequest) MergeSplit(_ context.Context, cfg exporterbatcher.MaxSizeConfig, r2 Request) ([]Request, error) {
@@ -33,6 +23,11 @@ func (req *logsRequest) MergeSplit(_ context.Context, cfg exporterbatcher.MaxSiz
 		}
 	}
 
+	if cfg.MaxSizeItems == 0 {
+		req2.ld.ResourceLogs().MoveAndAppendTo(req.ld.ResourceLogs())
+		return []Request{req}, nil
+	}
+
 	var (
 		res          []Request
 		destReq      *logsRequest

exporter/exporterhelper/logs_batch_test.go

@@ -19,15 +19,15 @@ import (
 func TestMergeLogs(t *testing.T) {
 	lr1 := &logsRequest{ld: testdata.GenerateLogs(2)}
 	lr2 := &logsRequest{ld: testdata.GenerateLogs(3)}
-	res, err := lr1.Merge(context.Background(), lr2)
+	res, err := lr1.MergeSplit(context.Background(), exporterbatcher.MaxSizeConfig{}, lr2)
 	require.NoError(t, err)
-	assert.Equal(t, 5, res.(*logsRequest).ld.LogRecordCount())
+	require.Equal(t, 5, res[0].(*logsRequest).ld.LogRecordCount())
 }
 
 func TestMergeLogsInvalidInput(t *testing.T) {
 	lr1 := &tracesRequest{td: testdata.GenerateTraces(2)}
 	lr2 := &logsRequest{ld: testdata.GenerateLogs(3)}
-	_, err := lr1.Merge(context.Background(), lr2)
+	_, err := lr1.MergeSplit(context.Background(), exporterbatcher.MaxSizeConfig{}, lr2)
 	require.Error(t, err)
 }
 

exporter/exporterhelper/metrics_batch.go

@@ -11,16 +11,6 @@ import (
 	"go.opentelemetry.io/collector/pdata/pmetric"
 )
 
-// Merge merges the provided metrics request into the current request and returns the merged request.
-func (req *metricsRequest) Merge(_ context.Context, r2 Request) (Request, error) {
-	mr2, ok2 := r2.(*metricsRequest)
-	if !ok2 {
-		return nil, errors.New("invalid input type")
-	}
-	mr2.md.ResourceMetrics().MoveAndAppendTo(req.md.ResourceMetrics())
-	return req, nil
-}
-
 // MergeSplit splits and/or merges the provided metrics request and the current request into one or more requests
 // conforming with the MaxSizeConfig.
 func (req *metricsRequest) MergeSplit(_ context.Context, cfg exporterbatcher.MaxSizeConfig, r2 Request) ([]Request, error) {
@@ -33,6 +23,11 @@ func (req *metricsRequest) MergeSplit(_ context.Context, cfg exporterbatcher.Max
 		}
 	}
 
+	if cfg.MaxSizeItems == 0 {
+		req2.md.ResourceMetrics().MoveAndAppendTo(req.md.ResourceMetrics())
+		return []Request{req}, nil
+	}
+
 	var (
 		res          []Request
 		destReq      *metricsRequest

exporter/exporterhelper/metrics_batch_test.go

@@ -18,15 +18,15 @@ import (
 func TestMergeMetrics(t *testing.T) {
 	mr1 := &metricsRequest{md: testdata.GenerateMetrics(2)}
 	mr2 := &metricsRequest{md: testdata.GenerateMetrics(3)}
-	res, err := mr1.Merge(context.Background(), mr2)
+	res, err := mr1.MergeSplit(context.Background(), exporterbatcher.MaxSizeConfig{}, mr2)
 	require.NoError(t, err)
-	assert.Equal(t, 5, res.(*metricsRequest).md.MetricCount())
+	assert.Equal(t, 5, res[0].(*metricsRequest).md.MetricCount())
 }
 
 func TestMergeMetricsInvalidInput(t *testing.T) {
 	mr1 := &tracesRequest{td: testdata.GenerateTraces(2)}
 	mr2 := &metricsRequest{md: testdata.GenerateMetrics(3)}
-	_, err := mr1.Merge(context.Background(), mr2)
+	_, err := mr1.MergeSplit(context.Background(), exporterbatcher.MaxSizeConfig{}, mr2)
 	require.Error(t, err)
 }
 

exporter/exporterhelper/traces_batch.go

@@ -11,16 +11,6 @@ import (
 	"go.opentelemetry.io/collector/pdata/ptrace"
 )
 
-// Merge merges the provided traces request into the current request and returns the merged request.
-func (req *tracesRequest) Merge(_ context.Context, r2 Request) (Request, error) {
-	tr2, ok2 := r2.(*tracesRequest)
-	if !ok2 {
-		return nil, errors.New("invalid input type")
-	}
-	tr2.td.ResourceSpans().MoveAndAppendTo(req.td.ResourceSpans())
-	return req, nil
-}
-
 // MergeSplit splits and/or merges the provided traces request and the current request into one or more requests
 // conforming with the MaxSizeConfig.
 func (req *tracesRequest) MergeSplit(_ context.Context, cfg exporterbatcher.MaxSizeConfig, r2 Request) ([]Request, error) {
@@ -33,6 +23,11 @@ func (req *tracesRequest) MergeSplit(_ context.Context, cfg exporterbatcher.MaxS
 		}
 	}
 
+	if cfg.MaxSizeItems == 0 {
+		req2.td.ResourceSpans().MoveAndAppendTo(req.td.ResourceSpans())
+		return []Request{req}, nil
+	}
+
 	var (
 		res          []Request
 		destReq      *tracesRequest

exporter/exporterhelper/traces_batch_test.go

@@ -18,15 +18,15 @@ import (
 func TestMergeTraces(t *testing.T) {
 	tr1 := &tracesRequest{td: testdata.GenerateTraces(2)}
 	tr2 := &tracesRequest{td: testdata.GenerateTraces(3)}
-	res, err := tr1.Merge(context.Background(), tr2)
+	res, err := tr1.MergeSplit(context.Background(), exporterbatcher.MaxSizeConfig{}, tr2)
 	require.NoError(t, err)
-	assert.Equal(t, 5, res.(*tracesRequest).td.SpanCount())
+	assert.Equal(t, 5, res[0].(*tracesRequest).td.SpanCount())
 }
 
 func TestMergeTracesInvalidInput(t *testing.T) {
 	tr1 := &logsRequest{ld: testdata.GenerateLogs(2)}
 	tr2 := &tracesRequest{td: testdata.GenerateTraces(3)}
-	_, err := tr1.Merge(context.Background(), tr2)
+	_, err := tr1.MergeSplit(context.Background(), exporterbatcher.MaxSizeConfig{}, tr2)
 	require.Error(t, err)
 }
 

exporter/exporterhelper/xexporterhelper/profiles_batch.go

@@ -12,31 +12,31 @@ import (
 	"go.opentelemetry.io/collector/pdata/pprofile"
 )
 
-// Merge merges two profiles requests into one.
-func (req *profilesRequest) Merge(_ context.Context, r2 exporterhelper.Request) (exporterhelper.Request, error) {
-	tr2, ok2 := r2.(*profilesRequest)
-	if !ok2 {
-		return nil, errors.New("invalid input type")
-	}
-	tr2.pd.ResourceProfiles().MoveAndAppendTo(req.pd.ResourceProfiles())
-	return req, nil
-}
-
 // MergeSplit splits and/or merges the profiles into multiple requests based on the MaxSizeConfig.
 func (req *profilesRequest) MergeSplit(_ context.Context, cfg exporterbatcher.MaxSizeConfig, r2 exporterhelper.Request) ([]exporterhelper.Request, error) {
+	var req2 *profilesRequest
+	if r2 != nil {
+		var ok bool
+		req2, ok = r2.(*profilesRequest)
+		if !ok {
+			return nil, errors.New("invalid input type")
+		}
+	}
+
+	if cfg.MaxSizeItems == 0 {
+		req2.pd.ResourceProfiles().MoveAndAppendTo(req.pd.ResourceProfiles())
+		return []exporterhelper.Request{req}, nil
+	}
+
 	var (
 		res          []exporterhelper.Request
 		destReq      *profilesRequest
 		capacityLeft = cfg.MaxSizeItems
 	)
-	for _, r := range []exporterhelper.Request{req, r2} {
-		if r == nil {
+	for _, srcReq := range []*profilesRequest{req, req2} {
+		if srcReq == nil {
 			continue
 		}
-		srcReq, ok := r.(*profilesRequest)
-		if !ok {
-			return nil, errors.New("invalid input type")
-		}
 		if srcReq.pd.SampleCount() <= capacityLeft {
 			if destReq == nil {
 				destReq = srcReq

exporter/exporterhelper/xexporterhelper/profiles_batch_test.go

@@ -21,16 +21,17 @@ import (
 func TestMergeProfiles(t *testing.T) {
 	pr1 := &profilesRequest{pd: testdata.GenerateProfiles(2)}
 	pr2 := &profilesRequest{pd: testdata.GenerateProfiles(3)}
-	res, err := pr1.Merge(context.Background(), pr2)
+	res, err := pr1.MergeSplit(context.Background(), exporterbatcher.MaxSizeConfig{}, pr2)
 	require.NoError(t, err)
-	fmt.Fprintf(os.Stdout, "%#v\n", res.(*profilesRequest).pd)
-	assert.Equal(t, 5, res.(*profilesRequest).pd.SampleCount())
+	assert.Len(t, res, 1)
+	fmt.Fprintf(os.Stdout, "%#v\n", res[0].(*profilesRequest).pd)
+	assert.Equal(t, 5, res[0].(*profilesRequest).pd.SampleCount())
 }
 
 func TestMergeProfilesInvalidInput(t *testing.T) {
 	pr1 := &dummyRequest{}
 	pr2 := &profilesRequest{pd: testdata.GenerateProfiles(3)}
-	_, err := pr2.Merge(context.Background(), pr1)
+	_, err := pr2.MergeSplit(context.Background(), exporterbatcher.MaxSizeConfig{}, pr1)
 	assert.Error(t, err)
 }
 
@@ -154,10 +155,6 @@ func (req *dummyRequest) ItemsCount() int {
 	return 1
 }
 
-func (req *dummyRequest) Merge(_ context.Context, _ exporterhelper.Request) (exporterhelper.Request, error) {
-	return nil, nil
-}
-
 func (req *dummyRequest) MergeSplit(_ context.Context, _ exporterbatcher.MaxSizeConfig, _ exporterhelper.Request) (
 	[]exporterhelper.Request, error,
 ) {

exporter/internal/queue/default_batcher.go

@@ -89,14 +89,15 @@ func (qb *DefaultBatcher) startReadingFlushingGoroutine() {
 						idxList: []uint64{idx},
 					}
 				} else {
-					mergedReq, mergeErr := qb.currentBatch.req.Merge(qb.currentBatch.ctx, req)
+					// TODO: consolidate implementation for the cases where MaxSizeConfig is specified and the case where it is not specified
+					mergedReq, mergeErr := qb.currentBatch.req.MergeSplit(qb.currentBatch.ctx, qb.batchCfg.MaxSizeConfig, req)
 					if mergeErr != nil {
 						qb.queue.OnProcessingFinished(idx, mergeErr)
 						qb.currentBatchMu.Unlock()
 						continue
 					}
 					qb.currentBatch = &batch{
-						req:     mergedReq,
+						req:     mergedReq[0],
 						ctx:     qb.currentBatch.ctx,
 						idxList: append(qb.currentBatch.idxList, idx),
 					}

exporter/internal/queue/fake_request_test.go

@@ -53,32 +53,25 @@ func (r *fakeRequest) ItemsCount() int {
 	return r.items
 }
 
-func (r *fakeRequest) Merge(_ context.Context,
-	r2 internal.Request,
-) (internal.Request, error) {
-	fr2 := r2.(*fakeRequest)
-	if fr2.mergeErr != nil {
-		return nil, fr2.mergeErr
-	}
-	return &fakeRequest{
-		items:     r.items + fr2.items,
-		sink:      r.sink,
-		exportErr: fr2.exportErr,
-		delay:     r.delay + fr2.delay,
-	}, nil
-}
-
-func (r *fakeRequest) MergeSplit(ctx context.Context, cfg exporterbatcher.MaxSizeConfig,
-	r2 internal.Request,
-) ([]internal.Request, error) {
+func (r *fakeRequest) MergeSplit(_ context.Context, cfg exporterbatcher.MaxSizeConfig, r2 internal.Request) ([]internal.Request, error) {
 	if r.mergeErr != nil {
 		return nil, r.mergeErr
 	}
 
 	maxItems := cfg.MaxSizeItems
 	if maxItems == 0 {
-		r, err := r.Merge(ctx, r2)
-		return []internal.Request{r}, err
+		fr2 := r2.(*fakeRequest)
+		if fr2.mergeErr != nil {
+			return nil, fr2.mergeErr
+		}
+		return []internal.Request{
+			&fakeRequest{
+				items:     r.items + fr2.items,
+				sink:      r.sink,
+				exportErr: fr2.exportErr,
+				delay:     r.delay + fr2.delay,
+			},
+		}, nil
 	}
 
 	var fr2 *fakeRequest

exporter/internal/request.go

@@ -19,14 +19,9 @@ type Request interface {
 	// sent. For example, for OTLP exporter, this value represents the number of spans,
 	// metric data points or log records.
 	ItemsCount() int
-	// Merge is a function that merges this request with another one into a single request.
-	// Do not mutate the requests passed to the function if error can be returned after mutation or if the exporter is
-	// marked as not mutable.
-	// Experimental: 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.
-	Merge(context.Context, Request) (Request, error)
 	// MergeSplit is a function that merge and/or splits this request with another one into multiple requests based on the
 	// configured limit provided in MaxSizeConfig.
+	// MergeSplit does not split if all fields in MaxSizeConfig are not initialized (zero).
 	// All the returned requests MUST have a number of items that does not exceed the maximum number of items.
 	// Size of the last returned request MUST be less or equal than the size of any other returned request.
 	// The original request MUST not be mutated if error is returned after mutation or if the exporter is