diff --git a/examples/dag.go b/examples/dag.go
index b8c8a83..f095153 100644
--- a/examples/dag.go
+++ b/examples/dag.go
@@ -4,11 +4,12 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"github.com/oarkflow/mq/consts"
-	"github.com/oarkflow/mq/examples/tasks"
 	"io"
 	"net/http"
 
+	"github.com/oarkflow/mq/consts"
+	"github.com/oarkflow/mq/examples/tasks"
+
 	"github.com/oarkflow/mq"
 	"github.com/oarkflow/mq/dag"
 )
@@ -24,10 +25,8 @@ func main() {
 	d.AddNode("C", tasks.Node3)
 	d.AddNode("D", tasks.Node4)
 	d.AddNode("E", tasks.Node5)
-	err := d.AddDeferredNode("F")
-	if err != nil {
-		panic(err)
-	}
+	d.AddNode("F", tasks.Node6)
+
 	d.AddEdge("A", "B", dag.LoopEdge)
 	d.AddCondition("C", map[string]string{"PASS": "D", "FAIL": "E"})
 	d.AddEdge("B", "C")
@@ -35,7 +34,7 @@ func main() {
 	d.AddEdge("E", "F")
 	http.HandleFunc("POST /publish", requestHandler("publish"))
 	http.HandleFunc("POST /request", requestHandler("request"))
-	err = d.Start(context.TODO(), ":8083")
+	err := d.Start(context.TODO(), ":8083")
 	if err != nil {
 		panic(err)
 	}
diff --git a/utils/retry.go b/utils/retry.go
index d3bdb0a..6ffe357 100644
--- a/utils/retry.go
+++ b/utils/retry.go
@@ -2,6 +2,7 @@ package utils
 
 import (
 	"math/rand"
+	"reflect"
 	"time"
 )
 
@@ -9,3 +10,18 @@ func CalculateJitter(baseDelay time.Duration, percent float64) time.Duration {
 	jitter := time.Duration(rand.Float64()*percent*float64(baseDelay)) - time.Duration(percent*float64(baseDelay)/2)
 	return baseDelay + jitter
 }
+
+func SizeOf(v any) uintptr {
+	val := reflect.ValueOf(v)
+	if val.Kind() == reflect.Ptr {
+		val = val.Elem()
+	}
+	switch val.Kind() {
+	case reflect.Slice:
+		return uintptr(val.Len()) * val.Type().Elem().Size()
+	case reflect.Map:
+		return uintptr(val.Len()) * (val.Type().Key().Size() + val.Type().Elem().Size())
+	default:
+		return val.Type().Size()
+	}
+}