[chore][pkg/stanza] refactor: introduce emit.Token struct (open-telem…

…etry#36260)

This makes the code clearer by encapsulating the token's body and
attributes in a single structure. It should make future change clearer
when the emit callback will be changed to accept a collection of tokens
as opposed to a single token.

The Sink type could use some refactoring as well, but I'm not doing it
here to keep the changes to the minimum for clarity and ease of code
review.

.chloggen/refactor-callback-token.yaml

@@ -0,0 +1,27 @@
+# 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. filelogreceiver)
+component: pkg/stanza
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Changed signature of `emit.Callback` function in `pkg/stanza/fileconsumer/emit` package by introducing `emit.Token` struct that encapsulates the token's body and attributes.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [36260]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# 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]

pkg/stanza/fileconsumer/benchmark_test.go

@@ -16,6 +16,7 @@ import (
 	"github.com/stretchr/testify/require"
 	"go.opentelemetry.io/collector/component/componenttest"
 
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza/fileconsumer/emit"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza/fileconsumer/internal/filetest"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza/fileconsumer/internal/fingerprint"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza/testutil"
@@ -187,8 +188,8 @@ func BenchmarkFileInput(b *testing.B) {
 			cfg.PollInterval = time.Microsecond
 
 			doneChan := make(chan bool, len(files))
-			callback := func(_ context.Context, token []byte, _ map[string]any) error {
-				if len(token) == 0 {
+			callback := func(_ context.Context, token emit.Token) error {
+				if len(token.Body) == 0 {
 					doneChan <- true
 				}
 				return nil

pkg/stanza/fileconsumer/emit/emit.go

@@ -7,4 +7,16 @@ import (
 	"context"
 )
 
-type Callback func(ctx context.Context, token []byte, attrs map[string]any) error
+type Callback func(ctx context.Context, token Token) error
+
+type Token struct {
+	Body       []byte
+	Attributes map[string]any
+}
+
+func NewToken(body []byte, attrs map[string]any) Token {
+	return Token{
+		Body:       body,
+		Attributes: attrs,
+	}
+}

pkg/stanza/fileconsumer/internal/emittest/nop.go

@@ -5,8 +5,10 @@ package emittest // import "github.com/open-telemetry/opentelemetry-collector-co
 
 import (
 	"context"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza/fileconsumer/emit"
 )
 
-func Nop(_ context.Context, _ []byte, _ map[string]any) error {
+func Nop(_ context.Context, _ emit.Token) error {
 	return nil
 }

pkg/stanza/fileconsumer/internal/emittest/nop_test.go

@@ -8,8 +8,10 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/require"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza/fileconsumer/emit"
 )
 
 func TestNop(t *testing.T) {
-	require.NoError(t, Nop(context.Background(), nil, nil))
+	require.NoError(t, Nop(context.Background(), emit.Token{}))
 }

pkg/stanza/fileconsumer/internal/emittest/sink.go

@@ -57,13 +57,13 @@ func NewSink(opts ...SinkOpt) *Sink {
 	return &Sink{
 		emitChan: emitChan,
 		timeout:  cfg.timeout,
-		Callback: func(ctx context.Context, token []byte, attrs map[string]any) error {
-			copied := make([]byte, len(token))
-			copy(copied, token)
+		Callback: func(ctx context.Context, token emit.Token) error {
+			copied := make([]byte, len(token.Body))
+			copy(copied, token.Body)
 			select {
 			case <-ctx.Done():
 				return ctx.Err()
-			case emitChan <- &Call{copied, attrs}:
+			case emitChan <- &Call{copied, token.Attributes}:
 			}
 			return nil
 		},

pkg/stanza/fileconsumer/internal/emittest/sink_test.go

@@ -11,6 +11,8 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza/fileconsumer/emit"
 )
 
 func TestNextToken(t *testing.T) {
@@ -202,7 +204,7 @@ func sinkTest(t *testing.T, opts ...SinkOpt) (*Sink, []*Call) {
 	}
 	go func() {
 		for _, c := range testCalls {
-			assert.NoError(t, s.Callback(context.Background(), c.Token, c.Attrs))
+			assert.NoError(t, s.Callback(context.Background(), emit.NewToken(c.Token, c.Attrs)))
 		}
 	}()
 	return s, testCalls

pkg/stanza/fileconsumer/internal/reader/reader.go

@@ -209,7 +209,7 @@ func (r *Reader) readContents(ctx context.Context) {
 			r.FileAttributes[attrs.LogFileRecordNumber] = r.RecordNum
 		}
 
-		err = r.emitFunc(ctx, token, r.FileAttributes)
+		err = r.emitFunc(ctx, emit.NewToken(token, r.FileAttributes))
 		if err != nil {
 			r.set.Logger.Error("failed to process token", zap.Error(err))
 		}

pkg/stanza/operator/input/file/input.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza/entry"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza/fileconsumer"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza/fileconsumer/emit"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza/operator"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza/operator/helper"
 )
@@ -36,17 +37,17 @@ func (i *Input) Stop() error {
 	return i.fileConsumer.Stop()
 }
 
-func (i *Input) emit(ctx context.Context, token []byte, attrs map[string]any) error {
-	if len(token) == 0 {
+func (i *Input) emit(ctx context.Context, token emit.Token) error {
+	if len(token.Body) == 0 {
 		return nil
 	}
 
-	ent, err := i.NewEntry(i.toBody(token))
+	ent, err := i.NewEntry(i.toBody(token.Body))
 	if err != nil {
 		return fmt.Errorf("create entry: %w", err)
 	}
 
-	for k, v := range attrs {
+	for k, v := range token.Attributes {
 		if err := ent.Set(entry.NewAttributeField(k), v); err != nil {
 			i.Logger().Error("set attribute", zap.Error(err))
 		}

receiver/otlpjsonfilereceiver/file.go

@@ -19,6 +19,7 @@ import (
 
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza/adapter"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza/fileconsumer"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza/fileconsumer/emit"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/otlpjsonfilereceiver/internal/metadata"
 )
 
@@ -82,10 +83,10 @@ func createLogsReceiver(_ context.Context, settings receiver.Settings, configura
 	if cfg.ReplayFile {
 		opts = append(opts, fileconsumer.WithNoTracking())
 	}
-	input, err := cfg.Config.Build(settings.TelemetrySettings, func(ctx context.Context, token []byte, _ map[string]any) error {
+	input, err := cfg.Config.Build(settings.TelemetrySettings, func(ctx context.Context, token emit.Token) error {
 		ctx = obsrecv.StartLogsOp(ctx)
 		var l plog.Logs
-		l, err = logsUnmarshaler.UnmarshalLogs(token)
+		l, err = logsUnmarshaler.UnmarshalLogs(token.Body)
 		if err != nil {
 			obsrecv.EndLogsOp(ctx, metadata.Type.String(), 0, err)
 		} else {
@@ -119,10 +120,10 @@ func createMetricsReceiver(_ context.Context, settings receiver.Settings, config
 	if cfg.ReplayFile {
 		opts = append(opts, fileconsumer.WithNoTracking())
 	}
-	input, err := cfg.Config.Build(settings.TelemetrySettings, func(ctx context.Context, token []byte, _ map[string]any) error {
+	input, err := cfg.Config.Build(settings.TelemetrySettings, func(ctx context.Context, token emit.Token) error {
 		ctx = obsrecv.StartMetricsOp(ctx)
 		var m pmetric.Metrics
-		m, err = metricsUnmarshaler.UnmarshalMetrics(token)
+		m, err = metricsUnmarshaler.UnmarshalMetrics(token.Body)
 		if err != nil {
 			obsrecv.EndMetricsOp(ctx, metadata.Type.String(), 0, err)
 		} else {
@@ -155,10 +156,10 @@ func createTracesReceiver(_ context.Context, settings receiver.Settings, configu
 	if cfg.ReplayFile {
 		opts = append(opts, fileconsumer.WithNoTracking())
 	}
-	input, err := cfg.Config.Build(settings.TelemetrySettings, func(ctx context.Context, token []byte, _ map[string]any) error {
+	input, err := cfg.Config.Build(settings.TelemetrySettings, func(ctx context.Context, token emit.Token) error {
 		ctx = obsrecv.StartTracesOp(ctx)
 		var t ptrace.Traces
-		t, err = tracesUnmarshaler.UnmarshalTraces(token)
+		t, err = tracesUnmarshaler.UnmarshalTraces(token.Body)
 		if err != nil {
 			obsrecv.EndTracesOp(ctx, metadata.Type.String(), 0, err)
 		} else {
@@ -183,8 +184,8 @@ func createProfilesReceiver(_ context.Context, settings receiver.Settings, confi
 	if cfg.ReplayFile {
 		opts = append(opts, fileconsumer.WithNoTracking())
 	}
-	input, err := cfg.Config.Build(settings.TelemetrySettings, func(ctx context.Context, token []byte, _ map[string]any) error {
-		p, _ := profilesUnmarshaler.UnmarshalProfiles(token)
+	input, err := cfg.Config.Build(settings.TelemetrySettings, func(ctx context.Context, token emit.Token) error {
+		p, _ := profilesUnmarshaler.UnmarshalProfiles(token.Body)
 		if p.ResourceProfiles().Len() != 0 {
 			_ = profiles.ConsumeProfiles(ctx, p)
 		}