Add support for text log format

Signed-off-by: Émile Ré <nemile.re@gmail.com>

Author: codenem

log/log.go

@@ -18,6 +18,7 @@ package log
 
 import (
 	"context"
+	"fmt"
 	"io"
 	"log/slog"
 	"os"
@@ -31,6 +32,7 @@ type (
 	// flexible output configuration.
 	Logger struct {
 		logger     *slog.Logger
+		format     Format
 		output     io.Writer
 		path       string
 		level      *slog.LevelVar
@@ -46,13 +48,18 @@ type (
 	// Attr represents an attribute (key-value pair) added to log
 	// entries for structured logging.
 	Attr = slog.Attr
+
+	Format = string
 )
 
 var (
 	LevelInfo  = slog.LevelInfo
 	LevelError = slog.LevelError
 	LevelWarn  = slog.LevelWarn
 	LevelDebug = slog.LevelDebug
+
+	FormatJSON Format = "json"
+	FormatText Format = "text"
 )
 
 // WithLevel sets the logging level for the Logger.
@@ -86,6 +93,12 @@ func WithAttributes(attrs ...Attr) Option {
 	}
 }
 
+func WithFormat(format Format) Option {
+	return func(l *Logger) {
+		l.format = format
+	}
+}
+
 // Any creates a key-value attribute with any data type.
 func Any(k string, v any) Attr {
 	return slog.Any(k, v)
@@ -143,20 +156,34 @@ func NewLogger(options ...Option) *Logger {
 	l := &Logger{
 		output: os.Stderr,
 		level:  new(slog.LevelVar),
+		format: FormatJSON,
 	}
 
 	for _, option := range options {
 		option(l)
 	}
 
-	handler := slog.NewJSONHandler(
-		l.output,
-		&slog.HandlerOptions{
-			Level: l.level,
-		},
-	).WithAttrs(l.attributes)
+	var handler slog.Handler
+	switch l.format {
+	case FormatText:
+		handler = slog.NewTextHandler(
+			l.output,
+			&slog.HandlerOptions{
+				Level: l.level,
+			},
+		)
+	case FormatJSON:
+		handler = slog.NewJSONHandler(
+			l.output,
+			&slog.HandlerOptions{
+				Level: l.level,
+			},
+		)
+	default:
+		panic(fmt.Errorf("unsupported format %s for logger %s", l.format, l.path))
+	}
 
-	l.logger = slog.New(handler)
+	l.logger = slog.New(handler.WithAttrs(l.attributes))
 
 	return l
 }
@@ -171,6 +198,7 @@ func (l *Logger) With(attrs ...Attr) *Logger {
 		WithAttributes(
 			append(l.attributes, attrs...)...,
 		),
+		WithFormat(l.format),
 	)
 }
 
@@ -187,6 +215,7 @@ func (l *Logger) Named(name string, options ...Option) *Logger {
 		WithOutput(l.output),
 		WithLevel(l.level.Level()),
 		WithAttributes(l.attributes...),
+		WithFormat(l.format),
 	}
 
 	options = append(inheritedOptions, options...)

unit/unit.go

@@ -84,15 +84,10 @@ type (
 
 func NewUnit(main Runnable, name, version, environment string) *Unit {
 	return &Unit{
-		name: name,
-		main: main,
-		logger: log.NewLogger(
-			log.WithName(name),
-			log.WithAttributes(
-				log.String("version", version),
-				log.String("environment", environment),
-			),
-		),
+		name:        name,
+		version:     version,
+		environment: environment,
+		main:        main,
 		config: &Config{
 			Metrics: MetricsConfig{
 				Addr: ":9090",
@@ -116,6 +111,7 @@ func (u *Unit) Run() error {
 func (u *Unit) RunContext(parentCtx context.Context) error {
 	filename := flag.String("cfg-file", "", "the path of the configuration file")
 	printCfg := flag.Bool("print-cfg", false, "print the loaded cfg and exit")
+	format := flag.String("format", "json", "log format")
 	help := flag.Bool("help", false, "show this help message")
 	version := flag.Bool("version", false, "show the service version")
 
@@ -153,6 +149,14 @@ func (u *Unit) RunContext(parentCtx context.Context) error {
 		return nil
 	}
 
+	u.logger = log.NewLogger(
+		log.WithName(u.name),
+		log.WithAttributes(
+			log.String("version", u.version),
+			log.String("environment", u.environment),
+		),
+		log.WithFormat(*format),
+	)
 	logger := u.logger.Named("unit")
 
 	ctx, cancel := context.WithCancelCause(parentCtx)