fix: resolve nonce race condition and eliminate redundant body parsing

Author: iczc

internal/chain/transaction.go

@@ -6,7 +6,7 @@ import (
 	"fmt"
 	"math/big"
 	"strings"
-	"sync/atomic"
+	"sync"
 
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/common"
@@ -22,6 +22,7 @@ type TxBuilder interface {
 }
 
 type TxBuild struct {
+	mu              sync.Mutex
 	client          bind.ContractTransactor
 	privateKey      *ecdsa.PrivateKey
 	signer          types.Signer
@@ -69,10 +70,12 @@ func (b *TxBuild) Transfer(ctx context.Context, to string, value *big.Int) (comm
 		return common.Hash{}, fmt.Errorf("invalid transfer value: must be positive")
 	}
 
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
 	gasLimit := uint64(21000)
 	toAddress := common.HexToAddress(to)
-
-	nonce := b.getAndIncrementNonce()
+	nonce := b.nonce
 
 	var err error
 	var unsignedTx *types.Transaction
@@ -99,6 +102,7 @@ func (b *TxBuild) Transfer(ctx context.Context, to string, value *big.Int) (comm
 		return common.Hash{}, err
 	}
 
+	b.nonce++
 	return signedTx.Hash(), nil
 }
 
@@ -143,10 +147,6 @@ func (b *TxBuild) buildLegacyTx(ctx context.Context, to *common.Address, value *
 	}), nil
 }
 
-func (b *TxBuild) getAndIncrementNonce() uint64 {
-	return atomic.AddUint64(&b.nonce, 1) - 1
-}
-
 func (b *TxBuild) refreshNonce(ctx context.Context) {
 	nonce, err := b.client.PendingNonceAt(ctx, b.Sender())
 	if err != nil {
@@ -157,7 +157,7 @@ func (b *TxBuild) refreshNonce(ctx context.Context) {
 		return
 	}
 
-	atomic.StoreUint64(&b.nonce, nonce)
+	b.nonce = nonce
 	log.WithField("nonce", nonce).Info("Nonce refreshed successfully")
 }
 

internal/server/dto.go

@@ -82,7 +82,6 @@ func decodeJSONBody(r *http.Request, dst interface{}) error {
 		}
 	}
 
-	r.Body = io.NopCloser(bytes.NewReader(body))
 	return nil
 }
 

internal/server/middleware.go

@@ -1,6 +1,7 @@
 package server
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"net"
@@ -15,6 +16,10 @@ import (
 	"github.com/urfave/negroni/v3"
 )
 
+type contextKey int
+
+const addressContextKey contextKey = iota
+
 type Limiter struct {
 	mutex      sync.Mutex
 	cache      *ttlcache.Cache
@@ -44,6 +49,8 @@ func (l *Limiter) ServeHTTP(w http.ResponseWriter, r *http.Request, next http.Ha
 		return
 	}
 
+	r = r.WithContext(context.WithValue(r.Context(), addressContextKey, address))
+
 	if l.ttl <= 0 {
 		next.ServeHTTP(w, r)
 		return

internal/server/server.go

@@ -17,15 +17,15 @@ import (
 )
 
 type Server struct {
-	chain.TxBuilder
+	txBuilder chain.TxBuilder
 	cfg       *Config
 	server    *http.Server
 	payoutWei *big.Int
 }
 
 func NewServer(builder chain.TxBuilder, cfg *Config) *Server {
 	return &Server{
-		TxBuilder: builder,
+		txBuilder: builder,
 		cfg:       cfg,
 		payoutWei: chain.EtherToWei(cfg.payout),
 	}
@@ -78,13 +78,16 @@ func (s *Server) handleClaim() http.HandlerFunc {
 			return
 		}
 
-		// Address has already been validated by limiter
-		address, _ := readAddress(r)
+		address, ok := r.Context().Value(addressContextKey).(string)
+		if !ok || address == "" {
+			renderJSON(w, claimResponse{Message: "invalid request"}, http.StatusBadRequest)
+			return
+		}
 
 		ctx, cancel := context.WithTimeout(r.Context(), 5*time.Second)
 		defer cancel()
 
-		txHash, err := s.Transfer(ctx, address, new(big.Int).Set(s.payoutWei))
+		txHash, err := s.txBuilder.Transfer(ctx, address, new(big.Int).Set(s.payoutWei))
 		if err != nil {
 			log.WithFields(log.Fields{
 				"error":   err,
@@ -110,7 +113,7 @@ func (s *Server) handleInfo() http.HandlerFunc {
 			return
 		}
 		renderJSON(w, infoResponse{
-			Account:         s.Sender().String(),
+			Account:         s.txBuilder.Sender().String(),
 			Network:         s.cfg.network,
 			Symbol:          s.cfg.symbol,
 			Payout:          strconv.FormatFloat(s.cfg.payout, 'f', -1, 64),

internal/server/server_test.go

@@ -3,11 +3,9 @@ package server
 import (
 	"context"
 	"encoding/json"
-	"fmt"
 	"math/big"
 	"net/http"
 	"net/http/httptest"
-	"strings"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -49,11 +47,11 @@ func TestHandleClaim(t *testing.T) {
 	mockBuilder.On("Transfer", mock.Anything, expectedAddress, expectedAmount).Return(common.Hash{1}, nil)
 
 	server := setupTestServer(mockBuilder)
-	reqBody := strings.NewReader(fmt.Sprintf(`{"address": "%s"}`, expectedAddress))
-	req, err := http.NewRequest("POST", "/api/claim", reqBody)
+	req, err := http.NewRequest("POST", "/api/claim", nil)
 	if err != nil {
 		t.Fatal(err)
 	}
+	req = req.WithContext(context.WithValue(req.Context(), addressContextKey, expectedAddress))
 
 	rr := httptest.NewRecorder()
 	handler := server.handleClaim()