[exporter/logging] Add exporter.logging.CreateLoggerFromCore featur…

…e gate

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### 💡 Enhancements 💡
 
 - Add `linux-ppc64le` architecture to cross build tests in CI
+- Add `exporter.logging.CreateLoggerFromCore` feature gate, to create the exporter's logger from the service's logger (#5677)
 
 ### 🧰 Bug fixes 🧰
 

exporter/loggingexporter/README.md

@@ -34,6 +34,12 @@ exporters:
     sampling_thereafter: 200
 ```
 
+## Feature gates
+
+The following feature gates are available:
+
+- `exporter.logging.CreateLoggerFromCore` ([alpha stability](../../service/featuregate#feature-lifecycle)): Create the logger from the service logger's core. This makes the logging exporter follow the `telemetry::logs` configuration. This will make the exporter fail to start if the `loglevel` is set lower than `telemetry::logs::level`.
+
 [contrib]: https://github.com/open-telemetry/opentelemetry-collector-releases/tree/main/distributions/otelcol-contrib
 [core]: https://github.com/open-telemetry/opentelemetry-collector-releases/tree/main/distributions/otelcol
 [In development]: https://github.com/open-telemetry/opentelemetry-collector#in-development

exporter/loggingexporter/factory.go

@@ -16,21 +16,39 @@ package loggingexporter // import "go.opentelemetry.io/collector/exporter/loggin
 
 import (
 	"context"
+	"fmt"
+	"sync"
+	"time"
 
 	"go.uber.org/zap"
 	"go.uber.org/zap/zapcore"
 
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/config"
+	"go.opentelemetry.io/collector/service/featuregate"
 )
 
 const (
 	// The value of "type" key in configuration.
 	typeStr                   = "logging"
 	defaultSamplingInitial    = 2
 	defaultSamplingThereafter = 500
+
+	// CreateLoggerFromCoreFeatureGate is a feature gate that, when enabled will create the logger from the service logger's core.
+	CreateLoggerFromCoreFeatureGate = "exporter.logging.CreateLoggerFromCore"
 )
 
+func init() {
+	featuregate.GetRegistry().Register(featuregate.Gate{
+		ID:          CreateLoggerFromCoreFeatureGate,
+		Description: "Use the service logger's core to build the logging exporter logger. When doing this, the `loglevel` field must not be lower than `telemetry::logs::level`.",
+		Enabled:     false,
+	})
+}
+
+// onceWarnFailedBuild is used to warn users about the future change to create the logger from core.
+var onceWarnFailedBuild sync.Once
+
 // NewFactory creates a factory for Logging exporter
 func NewFactory() component.ExporterFactory {
 	return component.NewExporterFactory(
@@ -54,7 +72,7 @@ func createDefaultConfig() config.Exporter {
 func createTracesExporter(_ context.Context, set component.ExporterCreateSettings, config config.Exporter) (component.TracesExporter, error) {
 	cfg := config.(*Config)
 
-	exporterLogger, err := createLogger(cfg)
+	exporterLogger, err := createLogger(cfg, set.TelemetrySettings.Logger)
 	if err != nil {
 		return nil, err
 	}
@@ -65,7 +83,7 @@ func createTracesExporter(_ context.Context, set component.ExporterCreateSetting
 func createMetricsExporter(_ context.Context, set component.ExporterCreateSettings, config config.Exporter) (component.MetricsExporter, error) {
 	cfg := config.(*Config)
 
-	exporterLogger, err := createLogger(cfg)
+	exporterLogger, err := createLogger(cfg, set.TelemetrySettings.Logger)
 	if err != nil {
 		return nil, err
 	}
@@ -76,15 +94,15 @@ func createMetricsExporter(_ context.Context, set component.ExporterCreateSettin
 func createLogsExporter(_ context.Context, set component.ExporterCreateSettings, config config.Exporter) (component.LogsExporter, error) {
 	cfg := config.(*Config)
 
-	exporterLogger, err := createLogger(cfg)
+	exporterLogger, err := createLogger(cfg, set.TelemetrySettings.Logger)
 	if err != nil {
 		return nil, err
 	}
 
 	return newLogsExporter(config, exporterLogger, set)
 }
 
-func createLogger(cfg *Config) (*zap.Logger, error) {
+func createIndependentLogger(cfg *Config) (*zap.Logger, error) {
 	// We take development config as the base since it matches the purpose
 	// of logging exporter being used for debugging reasons (so e.g. console encoder)
 	conf := zap.NewDevelopmentConfig()
@@ -100,3 +118,39 @@ func createLogger(cfg *Config) (*zap.Logger, error) {
 	}
 	return logginglogger, nil
 }
+
+func createLoggerFromCore(cfg *Config, logger *zap.Logger) (*zap.Logger, error) {
+	core := zapcore.NewSamplerWithOptions(
+		logger.Core(),
+		1*time.Second,
+		cfg.SamplingInitial,
+		cfg.SamplingThereafter,
+	)
+
+	core, err := zapcore.NewIncreaseLevelCore(core, cfg.LogLevel)
+	if err != nil {
+		return nil, fmt.Errorf("failed to increase log level: %w", err)
+	}
+
+	return zap.New(core), nil
+}
+
+func createLogger(cfg *Config, logger *zap.Logger) (*zap.Logger, error) {
+	// Always create the logger from core, to check if it would fail to build.
+	loggerFromCore, err := createLoggerFromCore(cfg, logger)
+
+	if featuregate.GetRegistry().IsEnabled(CreateLoggerFromCoreFeatureGate) {
+		return loggerFromCore, err
+	}
+
+	onceWarnFailedBuild.Do(func() {
+		if err != nil {
+			logger.Warn(
+				"This exporter will fail to start with the current configuration in a future version.",
+				zap.Error(err),
+				zap.String("related feature gate", CreateLoggerFromCoreFeatureGate),
+			)
+		}
+	})
+	return createIndependentLogger(cfg)
+}