etcdserver: fix wrong rev in header when nothing is actually got executed

etcdserver/apply.go

@@ -345,34 +345,23 @@ func (a *applierV3backend) Txn(rt *pb.TxnRequest) (*pb.TxnResponse, error) {
 		return nil, err
 	}
 
-	revision := a.s.KV().Rev()
-
 	// When executing the operations of txn, we need to hold the txn lock.
 	// So the reader will not see any intermediate results.
 	txnID := a.s.KV().TxnBegin()
-	defer func() {
-		err := a.s.KV().TxnEnd(txnID)
-		if err != nil {
-			panic(fmt.Sprint("unexpected error when closing txn", txnID))
-		}
-	}()
 
 	resps := make([]*pb.ResponseOp, len(reqs))
-	changedKV := false
 	for i := range reqs {
-		if reqs[i].GetRequestRange() == nil {
-			changedKV = true
-		}
 		resps[i] = a.applyUnion(txnID, reqs[i])
 	}
 
-	if changedKV {
-		revision += 1
+	err := a.s.KV().TxnEnd(txnID)
+	if err != nil {
+		panic(fmt.Sprint("unexpected error when closing txn", txnID))
 	}
 
 	txnResp := &pb.TxnResponse{}
 	txnResp.Header = &pb.ResponseHeader{}
-	txnResp.Header.Revision = revision
+	txnResp.Header.Revision = a.s.KV().Rev()
 	txnResp.Responses = resps
 	txnResp.Succeeded = ok
 	return txnResp, nil

integration/v3_grpc_test.go

@@ -288,6 +288,18 @@ func TestV3TxnRevision(t *testing.T) {
 		t.Fatalf("got rev %d, wanted rev %d", tresp.Header.Revision, presp.Header.Revision)
 	}
 
+	txndr := &pb.RequestOp{Request: &pb.RequestOp_RequestDeleteRange{RequestDeleteRange: &pb.DeleteRangeRequest{Key: []byte("def")}}}
+	txn = &pb.TxnRequest{Success: []*pb.RequestOp{txndr}}
+	tresp, err = kvc.Txn(context.TODO(), txn)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// did not update revision
+	if presp.Header.Revision != tresp.Header.Revision {
+		t.Fatalf("got rev %d, wanted rev %d", tresp.Header.Revision, presp.Header.Revision)
+	}
+
 	txnput := &pb.RequestOp{Request: &pb.RequestOp_RequestPut{RequestPut: &pb.PutRequest{Key: []byte("abc"), Value: []byte("123")}}}
 	txn = &pb.TxnRequest{Success: []*pb.RequestOp{txnput}}
 	tresp, err = kvc.Txn(context.TODO(), txn)