[exporter/file] Refactor to keep the file exporter inside start/stop lifecycle (#31495)

**Description:**
Scope the behavior of the fileexporter to its lifecycle, so it is safe
to shut it down or restart it.

**Link to tracking Issue:**
Fixes #31494

Author: atoulme

.chloggen/fileexporter_lifecycle.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: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: fileexporter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Scope the behavior of the fileexporter to its lifecycle, so it is safe to shut it down or restart it.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [27489]
+
+# (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: []

exporter/fileexporter/error_component.go

@@ -63,10 +63,7 @@ func createTracesExporter(
 	set exporter.CreateSettings,
 	cfg component.Config,
 ) (exporter.Traces, error) {
-	fe, err := getOrCreateFileExporter(cfg)
-	if err != nil {
-		return nil, err
-	}
+	fe := getOrCreateFileExporter(cfg)
 	return exporterhelper.NewTracesExporter(
 		ctx,
 		set,
@@ -83,10 +80,7 @@ func createMetricsExporter(
 	set exporter.CreateSettings,
 	cfg component.Config,
 ) (exporter.Metrics, error) {
-	fe, err := getOrCreateFileExporter(cfg)
-	if err != nil {
-		return nil, err
-	}
+	fe := getOrCreateFileExporter(cfg)
 	return exporterhelper.NewMetricsExporter(
 		ctx,
 		set,
@@ -103,10 +97,7 @@ func createLogsExporter(
 	set exporter.CreateSettings,
 	cfg component.Config,
 ) (exporter.Logs, error) {
-	fe, err := getOrCreateFileExporter(cfg)
-	if err != nil {
-		return nil, err
-	}
+	fe := getOrCreateFileExporter(cfg)
 	return exporterhelper.NewLogsExporter(
 		ctx,
 		set,
@@ -122,45 +113,20 @@ func createLogsExporter(
 // or returns the already cached one. Caching is required because the factory is asked trace and
 // metric receivers separately when it gets CreateTracesReceiver() and CreateMetricsReceiver()
 // but they must not create separate objects, they must use one Exporter object per configuration.
-func getOrCreateFileExporter(cfg component.Config) (FileExporter, error) {
+func getOrCreateFileExporter(cfg component.Config) FileExporter {
 	conf := cfg.(*Config)
 	fe := exporters.GetOrAdd(cfg, func() component.Component {
-		e, err := newFileExporter(conf)
-		if err != nil {
-			return &errorComponent{err: err}
-		}
-
-		return e
+		return newFileExporter(conf)
 	})
 
-	component := fe.Unwrap()
-	if errComponent, ok := component.(*errorComponent); ok {
-		return nil, errComponent.err
-	}
-
-	return component.(FileExporter), nil
+	c := fe.Unwrap()
+	return c.(FileExporter)
 }
 
-func newFileExporter(conf *Config) (FileExporter, error) {
-	marshaller := &marshaller{
-		formatType:       conf.FormatType,
-		tracesMarshaler:  tracesMarshalers[conf.FormatType],
-		metricsMarshaler: metricsMarshalers[conf.FormatType],
-		logsMarshaler:    logsMarshalers[conf.FormatType],
-		compression:      conf.Compression,
-		compressor:       buildCompressor(conf.Compression),
-	}
-	export := buildExportFunc(conf)
-
-	writer, err := newFileWriter(conf.Path, conf.Rotation, conf.FlushInterval, export)
-	if err != nil {
-		return nil, err
-	}
-
+func newFileExporter(conf *Config) FileExporter {
 	return &fileExporter{
-		marshaller: marshaller,
-		writer:     writer,
-	}, nil
+		conf: conf,
+	}
 }
 
 func newFileWriter(path string, rotation *Rotation, flushInterval time.Duration, export exportFunc) (*fileWriter, error) {

exporter/fileexporter/factory.go

@@ -26,10 +26,12 @@ func TestCreateMetricsExporterError(t *testing.T) {
 	cfg := &Config{
 		FormatType: formatTypeJSON,
 	}
-	_, err := createMetricsExporter(
+	e, err := createMetricsExporter(
 		context.Background(),
 		exportertest.NewNopCreateSettings(),
 		cfg)
+	require.NoError(t, err)
+	err = e.Start(context.Background(), componenttest.NewNopHost())
 	assert.Error(t, err)
 }
 
@@ -65,10 +67,12 @@ func TestCreateTracesExporterError(t *testing.T) {
 	cfg := &Config{
 		FormatType: formatTypeJSON,
 	}
-	_, err := createTracesExporter(
+	e, err := createTracesExporter(
 		context.Background(),
 		exportertest.NewNopCreateSettings(),
 		cfg)
+	require.NoError(t, err)
+	err = e.Start(context.Background(), componenttest.NewNopHost())
 	assert.Error(t, err)
 }
 
@@ -90,10 +94,12 @@ func TestCreateLogsExporterError(t *testing.T) {
 	cfg := &Config{
 		FormatType: formatTypeJSON,
 	}
-	_, err := createLogsExporter(
+	e, err := createLogsExporter(
 		context.Background(),
 		exportertest.NewNopCreateSettings(),
 		cfg)
+	require.NoError(t, err)
+	err = e.Start(context.Background(), componenttest.NewNopHost())
 	assert.Error(t, err)
 }
 

exporter/fileexporter/factory_test.go

@@ -14,6 +14,7 @@ import (
 
 // fileExporter is the implementation of file exporter that writes telemetry data to a file
 type fileExporter struct {
+	conf       *Config
 	marshaller *marshaller
 	writer     *fileWriter
 }
@@ -43,12 +44,33 @@ func (e *fileExporter) consumeLogs(_ context.Context, ld plog.Logs) error {
 }
 
 // Start starts the flush timer if set.
-func (e *fileExporter) Start(ctx context.Context, _ component.Host) error {
-	return e.writer.start(ctx)
+func (e *fileExporter) Start(_ context.Context, _ component.Host) error {
+	e.marshaller = &marshaller{
+		formatType:       e.conf.FormatType,
+		tracesMarshaler:  tracesMarshalers[e.conf.FormatType],
+		metricsMarshaler: metricsMarshalers[e.conf.FormatType],
+		logsMarshaler:    logsMarshalers[e.conf.FormatType],
+		compression:      e.conf.Compression,
+		compressor:       buildCompressor(e.conf.Compression),
+	}
+	export := buildExportFunc(e.conf)
+
+	var err error
+	e.writer, err = newFileWriter(e.conf.Path, e.conf.Rotation, e.conf.FlushInterval, export)
+	if err != nil {
+		return err
+	}
+	e.writer.start()
+	return nil
 }
 
 // Shutdown stops the exporter and is invoked during shutdown.
 // It stops the flush ticker if set.
 func (e *fileExporter) Shutdown(context.Context) error {
-	return e.writer.shutdown()
+	if e.writer == nil {
+		return nil
+	}
+	w := e.writer
+	e.writer = nil
+	return w.shutdown()
 }

exporter/fileexporter/file_exporter.go

@@ -126,16 +126,17 @@ func TestFileTracesExporter(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			conf := tt.args.conf
-			feI, err := newFileExporter(conf)
-			assert.NoError(t, err)
+			feI := newFileExporter(conf)
 			require.IsType(t, &fileExporter{}, feI)
 			fe := feI.(*fileExporter)
 
 			td := testdata.GenerateTracesTwoSpansSameResource()
 			assert.NoError(t, fe.Start(context.Background(), componenttest.NewNopHost()))
 			assert.NoError(t, fe.consumeTraces(context.Background(), td))
 			assert.NoError(t, fe.consumeTraces(context.Background(), td))
-			assert.NoError(t, fe.Shutdown(context.Background()))
+			defer func() {
+				assert.NoError(t, fe.Shutdown(context.Background()))
+			}()
 
 			fi, err := os.Open(fe.writer.path)
 			assert.NoError(t, err)
@@ -256,24 +257,18 @@ func TestFileMetricsExporter(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			conf := tt.args.conf
-			writer, err := buildFileWriter(conf)
-			assert.NoError(t, err)
 			fe := &fileExporter{
-				marshaller: &marshaller{
-					formatType:       conf.FormatType,
-					metricsMarshaler: metricsMarshalers[conf.FormatType],
-					compression:      conf.Compression,
-					compressor:       buildCompressor(conf.Compression),
-				},
-				writer: writer,
+				conf: conf,
 			}
 			require.NotNil(t, fe)
 
 			md := testdata.GenerateMetricsTwoMetrics()
 			assert.NoError(t, fe.Start(context.Background(), componenttest.NewNopHost()))
 			assert.NoError(t, fe.consumeMetrics(context.Background(), md))
 			assert.NoError(t, fe.consumeMetrics(context.Background(), md))
-			assert.NoError(t, fe.Shutdown(context.Background()))
+			defer func() {
+				assert.NoError(t, fe.Shutdown(context.Background()))
+			}()
 
 			fi, err := os.Open(fe.writer.path)
 			assert.NoError(t, err)
@@ -396,24 +391,18 @@ func TestFileLogsExporter(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			conf := tt.args.conf
-			writer, err := buildFileWriter(conf)
-			assert.NoError(t, err)
 			fe := &fileExporter{
-				marshaller: &marshaller{
-					formatType:    conf.FormatType,
-					logsMarshaler: logsMarshalers[conf.FormatType],
-					compression:   conf.Compression,
-					compressor:    buildCompressor(conf.Compression),
-				},
-				writer: writer,
+				conf: conf,
 			}
 			require.NotNil(t, fe)
 
 			ld := testdata.GenerateLogsTwoLogRecordsSameResource()
 			assert.NoError(t, fe.Start(context.Background(), componenttest.NewNopHost()))
 			assert.NoError(t, fe.consumeLogs(context.Background(), ld))
 			assert.NoError(t, fe.consumeLogs(context.Background(), ld))
-			assert.NoError(t, fe.Shutdown(context.Background()))
+			defer func() {
+				assert.NoError(t, fe.Shutdown(context.Background()))
+			}()
 
 			fi, err := os.Open(fe.writer.path)
 			assert.NoError(t, err)
@@ -631,11 +620,6 @@ func safeFileExporterWrite(e *fileExporter, d []byte) (int, error) {
 	return e.writer.file.Write(d)
 }
 
-func buildFileWriter(conf *Config) (*fileWriter, error) {
-	export := buildExportFunc(conf)
-	return newFileWriter(conf.Path, conf.Rotation, conf.FlushInterval, export)
-}
-
 func TestFlushing(t *testing.T) {
 	cfg := &Config{
 		Path:          tempFileName(t),
@@ -648,16 +632,28 @@ func TestFlushing(t *testing.T) {
 	// Wrap the buffer with the buffered writer closer that implements flush() method.
 	bwc := newBufferedWriteCloser(buf)
 	// Create a file exporter with flushing enabled.
-	feI, err := newFileExporter(cfg)
-	assert.NoError(t, err)
+	feI := newFileExporter(cfg)
 	assert.IsType(t, &fileExporter{}, feI)
 	fe := feI.(*fileExporter)
-	fe.writer.file.Close()
-	fe.writer.file = bwc
 
 	// Start the flusher.
 	ctx := context.Background()
-	assert.NoError(t, fe.Start(ctx, nil))
+	fe.marshaller = &marshaller{
+		formatType:       fe.conf.FormatType,
+		tracesMarshaler:  tracesMarshalers[fe.conf.FormatType],
+		metricsMarshaler: metricsMarshalers[fe.conf.FormatType],
+		logsMarshaler:    logsMarshalers[fe.conf.FormatType],
+		compression:      fe.conf.Compression,
+		compressor:       buildCompressor(fe.conf.Compression),
+	}
+	export := buildExportFunc(fe.conf)
+	var err error
+	fe.writer, err = newFileWriter(fe.conf.Path, fe.conf.Rotation, fe.conf.FlushInterval, export)
+	assert.NoError(t, err)
+	err = fe.writer.file.Close()
+	assert.NoError(t, err)
+	fe.writer.file = bwc
+	fe.writer.start()
 
 	// Write 10 bytes.
 	b := []byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}