Add header to target containing the sequence number (#470)

lib/attack.go

@@ -13,6 +13,8 @@ import (
 	"sync"
 	"time"
 
+	"strconv"
+
 	"golang.org/x/net/http2"
 )
 
@@ -344,7 +346,7 @@ func (a *Attacker) attack(tr Targeter, name string, workers *sync.WaitGroup, tic
 func (a *Attacker) hit(tr Targeter, name string) *Result {
 	var (
 		res = Result{Attack: name}
-		tgt Target
+		tgt = Target{Header: make(http.Header)}
 		err error
 	)
 
@@ -361,6 +363,8 @@ func (a *Attacker) hit(tr Targeter, name string) *Result {
 		}
 	}()
 
+	tgt.Header.Set("X-Vegeta-Seq", strconv.FormatUint(res.Seq, 10))
+
 	if err = tr(&tgt); err != nil {
 		a.Stop()
 		return &res

lib/attack_test.go

@@ -13,6 +13,7 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
@@ -358,3 +359,21 @@ func TestClient(t *testing.T) {
 		t.Errorf("Expected timeout error")
 	}
 }
+
+func TestSeqHeader(t *testing.T) {
+	t.Parallel()
+
+	var got http.Header
+
+	atk := NewAttacker()
+	for i := 0; i < 5; i++ {
+		res := atk.hit(func(trt *Target) error {
+			got = trt.Header
+			return nil
+		}, "")
+
+		if got.Get("X-Vegeta-Seq") != strconv.FormatUint(res.Seq, 10) {
+			t.Fatalf("got: %v, want: %v", got.Get("X-Vegeta-Seq"), res.Seq)
+		}
+	}
+}