feat(logger): add size/age/backup rotation for file output (#874)

apps/backend/cmd/kandev/main.go

@@ -136,6 +136,10 @@ func realMain() int {
 		Level:      cfg.Logging.Level,
 		Format:     cfg.Logging.Format,
 		OutputPath: cfg.Logging.OutputPath,
+		MaxSizeMB:  cfg.Logging.MaxSizeMB,
+		MaxBackups: cfg.Logging.MaxBackups,
+		MaxAgeDays: cfg.Logging.MaxAgeDays,
+		Compress:   cfg.Logging.Compress,
 	})
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Failed to initialize logger: %v\n", err)

apps/backend/go.mod

@@ -109,6 +109,7 @@ require (
 	google.golang.org/grpc v1.80.0 // indirect
 	google.golang.org/protobuf v1.36.11 // indirect
 	gopkg.in/ini.v1 v1.67.0 // indirect
+	gopkg.in/natefinch/lumberjack.v2 v2.2.1 // indirect
 	gotest.tools/v3 v3.5.2 // indirect
 )
 

apps/backend/go.sum

@@ -683,6 +683,8 @@ gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EV
 gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
 gopkg.in/ini.v1 v1.67.0 h1:Dgnx+6+nfE+IfzjUEISNeydPJh9AXNNsWbGP9KzCsOA=
 gopkg.in/ini.v1 v1.67.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=
+gopkg.in/natefinch/lumberjack.v2 v2.2.1 h1:bBRl1b0OH9s/DuPhuXpNl+VtCaJXFZ5/uEFST95x9zc=
+gopkg.in/natefinch/lumberjack.v2 v2.2.1/go.mod h1:YD8tP3GAjkrDg1eZH7EGmyESg/lsYskCTPBJVb9jqSc=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

apps/backend/internal/common/config/config.go

@@ -140,6 +140,13 @@ type LoggingConfig struct {
 	Level      string `mapstructure:"level"`
 	Format     string `mapstructure:"format"`
 	OutputPath string `mapstructure:"outputPath"`
+
+	// Rotation options — apply only when OutputPath is a file path
+	// (ignored for stdout/stderr). Backed by lumberjack.
+	MaxSizeMB  int  `mapstructure:"maxSizeMb"`
+	MaxBackups int  `mapstructure:"maxBackups"`
+	MaxAgeDays int  `mapstructure:"maxAgeDays"`
+	Compress   bool `mapstructure:"compress"`
 }
 
 // RepositoryDiscoveryConfig holds configuration for local repository scanning.
@@ -271,6 +278,10 @@ func setDefaults(v *viper.Viper) {
 	v.SetDefault("logging.level", "info")
 	v.SetDefault("logging.format", detectDefaultLogFormat())
 	v.SetDefault("logging.outputPath", "stdout")
+	v.SetDefault("logging.maxSizeMb", 100)
+	v.SetDefault("logging.maxBackups", 5)
+	v.SetDefault("logging.maxAgeDays", 30)
+	v.SetDefault("logging.compress", true)
 
 	// Repository discovery defaults
 	v.SetDefault("repositoryDiscovery.roots", []string{})

apps/backend/internal/common/logger/logger.go

@@ -8,6 +8,7 @@ import (
 
 	"go.uber.org/zap"
 	"go.uber.org/zap/zapcore"
+	"gopkg.in/natefinch/lumberjack.v2"
 
 	"github.com/kandev/kandev/internal/common/logger/buffer"
 )
@@ -25,6 +26,13 @@ type LoggingConfig struct {
 	Level      string `mapstructure:"level"`       // debug, info, warn, error
 	Format     string `mapstructure:"format"`      // json, console
 	OutputPath string `mapstructure:"output_path"` // stdout, stderr, or file path
+
+	// Rotation options — apply only when OutputPath is a file path
+	// (ignored for stdout/stderr). Backed by lumberjack.
+	MaxSizeMB  int  `mapstructure:"max_size_mb"`  // rotate when file exceeds this size; 0 = lumberjack default (100MB)
+	MaxBackups int  `mapstructure:"max_backups"`  // max number of rotated files to retain; 0 = unlimited
+	MaxAgeDays int  `mapstructure:"max_age_days"` // max age of rotated files; 0 = unlimited
+	Compress   bool `mapstructure:"compress"`     // gzip rotated files
 }
 
 // Logger wraps zap.Logger to provide structured logging with helper methods.
@@ -94,11 +102,13 @@ func NewLogger(cfg LoggingConfig) (*Logger, error) {
 	case "stderr":
 		writeSyncer = zapcore.AddSync(os.Stderr)
 	default:
-		file, err := os.OpenFile(cfg.OutputPath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
-		if err != nil {
-			return nil, err
-		}
-		writeSyncer = zapcore.AddSync(file)
+		writeSyncer = zapcore.AddSync(&lumberjack.Logger{
+			Filename:   cfg.OutputPath,
+			MaxSize:    cfg.MaxSizeMB,
+			MaxBackups: cfg.MaxBackups,
+			MaxAge:     cfg.MaxAgeDays,
+			Compress:   cfg.Compress,
+		})
 	}
 
 	outputCore := zapcore.NewCore(encoder, writeSyncer, level)