feat: add OutputFile option for log destination in logger

logger/options.go

@@ -15,6 +15,7 @@ package logger
 
 import (
 	"fmt"
+	"os"
 )
 
 const (
@@ -33,6 +34,9 @@ type Options struct {
 
 	// OutputLevel is the level of logging
 	OutputLevel string
+
+	// OutputFile is the destination file path for logs.
+	OutputFile string
 }
 
 // SetOutputLevel sets the log output level.
@@ -62,6 +66,11 @@ func (o *Options) AttachCmdFlags(
 			"log-level",
 			defaultOutputLevel,
 			"Options are debug, info, warn, error, or fatal (default info)")
+		stringVar(
+			&o.OutputFile,
+			"log-file",
+			"",
+			"Path to a file where logs will be written")
 	}
 
 	if boolVar != nil {
@@ -79,6 +88,7 @@ func DefaultOptions() Options {
 		JSONFormatEnabled: defaultJSONOutput,
 		appID:             undefinedAppID,
 		OutputLevel:       defaultOutputLevel,
+		OutputFile:        "",
 	}
 }
 
@@ -104,5 +114,16 @@ func ApplyOptionsToLoggers(options *Options) error {
 		v.SetOutputLevel(daprLogLevel)
 	}
 
+	if options.OutputFile != "" {
+		file, err := os.OpenFile(options.OutputFile, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0o600)
+		if err != nil {
+			return fmt.Errorf("failed to open log file %q: %w", options.OutputFile, err)
+		}
+
+		for _, v := range internalLoggers {
+			v.SetOutput(file)
+		}
+	}
+
 	return nil
 }

logger/options_test.go

@@ -14,6 +14,8 @@ limitations under the License.
 package logger
 
 import (
+	"os"
+	"path/filepath"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -26,6 +28,7 @@ func TestOptions(t *testing.T) {
 		assert.Equal(t, defaultJSONOutput, o.JSONFormatEnabled)
 		assert.Equal(t, undefinedAppID, o.appID)
 		assert.Equal(t, defaultOutputLevel, o.OutputLevel)
+		assert.Empty(t, o.OutputFile)
 	})
 
 	t.Run("set dapr ID", func(t *testing.T) {
@@ -40,10 +43,15 @@ func TestOptions(t *testing.T) {
 		o := DefaultOptions()
 
 		logLevelAsserted := false
+		logFileAsserted := false
 		testStringVarFn := func(p *string, name string, value string, usage string) {
 			if name == "log-level" && value == defaultOutputLevel {
 				logLevelAsserted = true
 			}
+
+			if name == "log-file" && value == "" {
+				logFileAsserted = true
+			}
 		}
 
 		logAsJSONAsserted := false
@@ -57,6 +65,7 @@ func TestOptions(t *testing.T) {
 
 		// assert
 		assert.True(t, logLevelAsserted)
+		assert.True(t, logFileAsserted)
 		assert.True(t, logAsJSONAsserted)
 	})
 }
@@ -92,3 +101,36 @@ func TestApplyOptionsToLoggers(t *testing.T) {
 			(l.(*daprLogger)).logger.Logger.GetLevel())
 	}
 }
+
+func TestApplyOptionsToLoggersFileOutput(t *testing.T) {
+	logPath := filepath.Join(t.TempDir(), "dapr.log")
+
+	testOptions := Options{
+		OutputLevel: "debug",
+		OutputFile:  logPath,
+	}
+
+	l := NewLogger("testLoggerFileOutput")
+
+	require.NoError(t, ApplyOptionsToLoggers(&testOptions))
+
+	dl, ok := l.(*daprLogger)
+	require.True(t, ok)
+	fileOut, ok := dl.logger.Logger.Out.(*os.File)
+	require.True(t, ok)
+	assert.Equal(t, logPath, fileOut.Name())
+	t.Cleanup(func() {
+		for _, logger := range getLoggers() {
+			logger.SetOutput(os.Stdout)
+		}
+
+		require.NoError(t, fileOut.Close())
+	})
+
+	msg := "log-file-test-message"
+	l.Info(msg)
+
+	b, err := os.ReadFile(logPath)
+	require.NoError(t, err)
+	assert.Contains(t, string(b), msg)
+}