Cherry-pick #17448 to 7.x: Postpone selection of the logger ou… (#17454)

(cherry picked from commit d6c2aac)

libbeat/logp/config.go

@@ -38,6 +38,7 @@ type Config struct {
 
 	Files FileConfig `config:"files"`
 
+	environment Environment
 	addCaller   bool // Adds package and line number info to messages.
 	development bool // Controls how DPanic behaves.
 }
@@ -59,41 +60,16 @@ const defaultLevel = InfoLevel
 // DefaultConfig returns the default config options for a given environment the
 // Beat is supposed to be run within.
 func DefaultConfig(environment Environment) Config {
-	switch environment {
-	case SystemdEnvironment, ContainerEnvironment:
-		return defaultToStderrConfig()
-
-	case MacOSServiceEnvironment, WindowsServiceEnvironment:
-		fallthrough
-	default:
-		return defaultToFileConfig()
-	}
-}
-
-func defaultToStderrConfig() Config {
 	return Config{
-		Level:     defaultLevel,
-		ToStderr:  true,
-		Files:     defaultFileConfig(),
-		addCaller: true,
-	}
-}
-
-func defaultToFileConfig() Config {
-	return Config{
-		Level:     defaultLevel,
-		ToFiles:   true,
-		Files:     defaultFileConfig(),
-		addCaller: true,
-	}
-}
-
-func defaultFileConfig() FileConfig {
-	return FileConfig{
-		MaxSize:         10 * 1024 * 1024,
-		MaxBackups:      7,
-		Permissions:     0600,
-		Interval:        0,
-		RotateOnStartup: true,
+		Level: defaultLevel,
+		Files: FileConfig{
+			MaxSize:         10 * 1024 * 1024,
+			MaxBackups:      7,
+			Permissions:     0600,
+			Interval:        0,
+			RotateOnStartup: true,
+		},
+		environment: environment,
+		addCaller:   true,
 	}
 }

libbeat/logp/core.go

@@ -67,21 +67,10 @@ func Configure(cfg Config) error {
 	)
 
 	// Build a single output (stderr has priority if more than one are enabled).
-	switch {
-	case cfg.toObserver:
+	if cfg.toObserver {
 		sink, observedLogs = observer.New(cfg.Level.zapLevel())
-	case cfg.toIODiscard:
-		sink, err = makeDiscardOutput(cfg)
-	case cfg.ToStderr:
-		sink, err = makeStderrOutput(cfg)
-	case cfg.ToSyslog:
-		sink, err = makeSyslogOutput(cfg)
-	case cfg.ToEventLog:
-		sink, err = makeEventLogOutput(cfg)
-	case cfg.ToFiles:
-		fallthrough
-	default:
-		sink, err = makeFileOutput(cfg)
+	} else {
+		sink, err = createLogOutput(cfg)
 	}
 	if err != nil {
 		return errors.Wrap(err, "failed to build log output")
@@ -125,6 +114,30 @@ func Configure(cfg Config) error {
 	return nil
 }
 
+func createLogOutput(cfg Config) (zapcore.Core, error) {
+	switch {
+	case cfg.toIODiscard:
+		return makeDiscardOutput(cfg)
+	case cfg.ToStderr:
+		return makeStderrOutput(cfg)
+	case cfg.ToSyslog:
+		return makeSyslogOutput(cfg)
+	case cfg.ToEventLog:
+		return makeEventLogOutput(cfg)
+	case cfg.ToFiles:
+		return makeFileOutput(cfg)
+	}
+
+	switch cfg.environment {
+	case SystemdEnvironment, ContainerEnvironment:
+		return makeStderrOutput(cfg)
+	case MacOSServiceEnvironment, WindowsServiceEnvironment:
+		fallthrough
+	default:
+		return makeFileOutput(cfg)
+	}
+}
+
 // DevelopmentSetup configures the logger in development mode at debug level.
 // By default the output goes to stderr.
 func DevelopmentSetup(options ...Option) error {