[exporter/debug] Add output_paths configuration option

Adds output_paths config field to debug exporter, allowing users to
redirect output to stderr or file paths when use_internal_logger is false.

- Extends Config struct with OutputPaths []string field
- Updates createCustomLogger to honor configured paths (defaults to stdout)
- Adds validation to prevent use with use_internal_logger=true
- Adds validation to reject empty path values
- Updates README with new configuration option
- Adds test coverage for output_paths scenarios

Fixes #10472

Author: Arunodoy18

.chloggen/debugexporter-output-paths.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. receiver/otlp)
+component: exporter/debug
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add `output_paths` configuration option to allow redirecting output when `use_internal_logger` is false
+
+# One or more tracking issues or pull requests related to the change
+issues: [10472]
+
+# (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: |
+  The `output_paths` option accepts an array of destinations (stdout, stderr, or file paths) and defaults to stdout.
+  This option can only be used when `use_internal_logger` is set to false.
+
+# 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: [user]

exporter/debugexporter/README.md

@@ -38,6 +38,7 @@ The following settings are optional:
   Refer to [Zap docs](https://godoc.org/go.uber.org/zap/zapcore#NewSampler) for more details
   on how sampling parameters impact number of messages.
 - `use_internal_logger` (default = `true`): uses the collector's internal logger for output. See [below](#using-the-collectors-internal-logger) for description.
+- `output_paths` (default = `[stdout]` when `use_internal_logger` is `false`): list of destinations for the exporter's output when bypassing the collector logger. Accepts `stdout`, `stderr`, or filesystem paths supported by Zap.
 - `sending_queue` (disabled by default): see [Sending Queue](../exporterhelper/README.md#sending-queue) for the full set of available options.
 
 Example configuration:
@@ -138,7 +139,7 @@ This comes with the following consequences:
 
 When `use_internal_logger` is set to `false`, the exporter does not use the collector's internal logger.
 Changing the values in `service::telemetry::logs` has no effect on the exporter's output.
-The exporter's output is sent to `stdout`.
+The exporter's output is sent to `stdout` by default and can be redirected via `output_paths`.
 
 [internal_telemetry]: https://opentelemetry.io/docs/collector/internal-telemetry/
 [internal_logs_config]: https://opentelemetry.io/docs/collector/internal-telemetry/#configure-internal-logs

exporter/debugexporter/config.go

@@ -34,6 +34,9 @@ type Config struct {
 	// UseInternalLogger defines whether the exporter sends the output to the collector's internal logger.
 	UseInternalLogger bool `mapstructure:"use_internal_logger"`
 
+	// OutputPaths holds the list of destinations for the exporter's output when UseInternalLogger is false.
+	OutputPaths []string `mapstructure:"output_paths"`
+
 	QueueConfig configoptional.Optional[exporterhelper.QueueBatchConfig] `mapstructure:"sending_queue"`
 
 	// prevent unkeyed literal initialization
@@ -48,5 +51,16 @@ func (cfg *Config) Validate() error {
 		return fmt.Errorf("verbosity level %q is not supported", cfg.Verbosity)
 	}
 
+	if len(cfg.OutputPaths) > 0 {
+		if cfg.UseInternalLogger {
+			return fmt.Errorf("output_paths requires use_internal_logger to be false")
+		}
+		for _, path := range cfg.OutputPaths {
+			if path == "" {
+				return fmt.Errorf("output_paths cannot contain empty values")
+			}
+		}
+	}
+
 	return nil
 }

exporter/debugexporter/config_test.go

@@ -37,6 +37,7 @@ func TestUnmarshalConfig(t *testing.T) {
 				Verbosity:          configtelemetry.LevelDetailed,
 				SamplingInitial:    10,
 				SamplingThereafter: 50,
+				OutputPaths:        []string{"stderr"},
 				QueueConfig:        configoptional.Default(queueCfg),
 			},
 		},
@@ -81,6 +82,16 @@ func Test_UnmarshalMarshalled(t *testing.T) {
 				Verbosity: configtelemetry.LevelDetailed,
 			},
 		},
+		"OutputPathsSpecified": {
+			inCfg: &Config{
+				UseInternalLogger: false,
+				OutputPaths:       []string{"stderr"},
+			},
+			expectedConfig: &Config{
+				UseInternalLogger: false,
+				OutputPaths:       []string{"stderr"},
+			},
+		},
 	} {
 		t.Run(name, func(t *testing.T) {
 			conf := confmap.New()
@@ -125,6 +136,29 @@ func TestValidate(t *testing.T) {
 				Verbosity: configtelemetry.LevelDetailed,
 			},
 		},
+		{
+			name: "output paths with internal logger",
+			cfg: &Config{
+				UseInternalLogger: true,
+				OutputPaths:       []string{"stderr"},
+			},
+			expectedErr: "output_paths requires use_internal_logger to be false",
+		},
+		{
+			name: "output paths empty entry",
+			cfg: &Config{
+				UseInternalLogger: false,
+				OutputPaths:       []string{""},
+			},
+			expectedErr: "output_paths cannot contain empty values",
+		},
+		{
+			name: "output paths valid",
+			cfg: &Config{
+				UseInternalLogger: false,
+				OutputPaths:       []string{"stderr"},
+			},
+		},
 	}
 
 	for _, tt := range tests {

exporter/debugexporter/exporter_test.go

@@ -128,6 +128,17 @@ func createTestCases() []testCase {
 				return cfg
 			}(),
 		},
+		{
+			name: "custom output paths",
+			config: func() *Config {
+				cfg := createDefaultConfig().(*Config)
+				cfg.QueueConfig = configoptional.Some(exporterhelper.NewDefaultQueueConfig())
+				cfg.QueueConfig.Get().QueueSize = 10
+				cfg.UseInternalLogger = false
+				cfg.OutputPaths = []string{"stderr"}
+				return cfg
+			}(),
+		},
 	}
 }
 

exporter/debugexporter/factory.go

@@ -126,6 +126,10 @@ func createCustomLogger(exporterConfig *Config) *zap.Logger {
 	encoderConfig.LevelKey = ""
 	// Do not prefix the output with current timestamp.
 	encoderConfig.TimeKey = ""
+	outputPaths := exporterConfig.OutputPaths
+	if len(outputPaths) == 0 {
+		outputPaths = []string{"stdout"}
+	}
 	zapConfig := zap.Config{
 		Level:         zap.NewAtomicLevelAt(zap.InfoLevel),
 		DisableCaller: true,
@@ -135,8 +139,8 @@ func createCustomLogger(exporterConfig *Config) *zap.Logger {
 		},
 		Encoding:      "console",
 		EncoderConfig: encoderConfig,
-		// Send exporter's output to stdout. This should be made configurable.
-		OutputPaths: []string{"stdout"},
+		// Honor optional output paths (stdout by default).
+		OutputPaths: outputPaths,
 	}
 	return zap.Must(zapConfig.Build())
 }

exporter/debugexporter/testdata/config_verbosity.yaml

@@ -2,3 +2,5 @@ verbosity: detailed
 sampling_initial: 10
 sampling_thereafter: 50
 use_internal_logger: false
+output_paths:
+	- stderr