diff --git a/history/helper.go b/history/helper.go
index da3e7ca..3a37ddb 100644
--- a/history/helper.go
+++ b/history/helper.go
@@ -9,7 +9,7 @@ import (
 func Error() *History {
 	h := getBase()
 	h.Type = ERROR
-	if !PROD {
+	if !util.PROD {
 		h.Trace = util.Stack()
 	}
 	return h
diff --git a/history/history.go b/history/history.go
index cb19465..d583992 100644
--- a/history/history.go
+++ b/history/history.go
@@ -12,8 +12,6 @@ import (
 	"kumoly.io/kumoly/app/store"
 )
 
-var PROD = false
-
 const (
 	ERROR = "ERROR"
 	INFO  = "INFO"
diff --git a/history/service.go b/history/service.go
index bc6e54a..33afdf6 100644
--- a/history/service.go
+++ b/history/service.go
@@ -2,7 +2,6 @@ package history
 
 import (
 	"github.com/rs/zerolog/log"
-	"github.com/spf13/viper"
 	"kumoly.io/kumoly/app/store"
 )
 
@@ -14,7 +13,6 @@ func (srv Service) IsService() bool           { return true }
 func (srv Service) GetDependencies() []string { return []string{"server.Service"} }
 
 func (srv Service) Init() error {
-	PROD = viper.GetBool("prod")
 	l := log.With().Str("mod", "history").
 		Str("service", "history.Service").
 		Logger()
diff --git a/server/middleware.go b/server/middleware.go
index 6b5eb68..d5f9ec1 100644
--- a/server/middleware.go
+++ b/server/middleware.go
@@ -8,6 +8,7 @@ import (
 	"github.com/gin-gonic/gin"
 	"github.com/rs/zerolog"
 	"kumoly.io/kumoly/app/errors"
+	"kumoly.io/kumoly/app/util"
 )
 
 func (srv *Service) Default(c *gin.Context) {
@@ -31,6 +32,9 @@ func (srv *Service) Default(c *gin.Context) {
 				c.Abort()
 				cl.Str("error", fmt.Sprint(err))
 			}
+			if !util.PROD {
+				cl.Str("trace", util.Stack())
+			}
 		} else if c.Writer.Status() >= 400 {
 			cl = srv.l.Error().Strs("error", c.Errors.Errors())
 		} else {
diff --git a/system/setup.go b/system/setup.go
index 1e4803c..cf3f53f 100644
--- a/system/setup.go
+++ b/system/setup.go
@@ -27,7 +27,7 @@ func init() {
 	viper.SetDefault("domain", "kumoly.io")
 	viper.SetDefault("timezone", "Asia/Taipei")
 	// mode [prod, dev]
-	viper.SetDefault("prod", PROD)
+	viper.SetDefault("prod", true)
 
 	// log.level : [-1(trace):5(panic)] 7 to disable
 	viper.SetDefault("log.level", int(zerolog.InfoLevel))
@@ -50,7 +50,8 @@ func Setup() {
 	zerolog.TimeFieldFormat = zerolog.TimeFormatUnix
 	zerolog.DurationFieldInteger = true
 	zerolog.SetGlobalLevel(zerolog.Level(viper.GetInt("log.level")))
-	if !viper.GetBool("prod") {
+	util.PROD = viper.GetBool("prod")
+	if util.PROD {
 		log.Logger = log.With().Caller().Logger()
 	}
 	if viper.GetBool("log.pretty") {
diff --git a/system/system.go b/system/system.go
index e8fbc17..52cc9ab 100644
--- a/system/system.go
+++ b/system/system.go
@@ -11,9 +11,9 @@ import (
 	"github.com/rs/zerolog/log"
 	"github.com/spf13/viper"
 	"kumoly.io/kumoly/app/history"
+	"kumoly.io/kumoly/app/util"
 )
 
-var PROD = true
 var l zerolog.Logger
 
 func init() {
@@ -77,7 +77,7 @@ func (sys *System) order() {
 	for i := range nodes {
 		sys.services = append(sys.services, *nodes[i].srv)
 	}
-	if !PROD {
+	if !util.PROD {
 		seq := ""
 		for i := range sys.services {
 			seq += sys.services[i].GetName()
diff --git a/task/task.go b/task/task.go
index 0a9e355..9f4388c 100644
--- a/task/task.go
+++ b/task/task.go
@@ -61,9 +61,12 @@ func (t *_task) Run() {
 	}
 	defer func() {
 		if err := recover(); err != nil {
-			l.Error().Str("task_id", t.Task.ID).
-				Str("task_name", t.name).Str("trace", util.Stack()).
-				Str("error", fmt.Sprint(err)).Msg("task paniced")
+			le := l.Error().Str("task_id", t.Task.ID).Str("task_name", t.name).
+				Str("error", fmt.Sprint(err))
+			if !util.PROD {
+				le.Str("trace", util.Stack())
+			}
+			le.Msg("task paniced")
 
 		} else if t.once {
 			c.Remove(t.id)
diff --git a/util/util.go b/util/util.go
index 6dc992f..dc2f658 100644
--- a/util/util.go
+++ b/util/util.go
@@ -5,6 +5,8 @@ import (
 	"path/filepath"
 )
 
+var PROD bool = true
+
 func Mkdir(args ...interface{}) error {
 	var path string
 	var mode os.FileMode