Ignore duplicate transactions that occur at same time (#31)

Author: ilayaraja89

models/transactions.go

@@ -7,6 +7,7 @@ import (
 	"time"
 
 	ledgerError "github.com/RealImage/QLedger/errors"
+	"github.com/lib/pq"
 	"github.com/pkg/errors"
 )
 
@@ -132,6 +133,15 @@ func (t *TransactionDB) Transact(txn *Transaction) bool {
 
 	_, err = tx.Exec("INSERT INTO transactions (id, timestamp, data) VALUES ($1, $2, $3)", txn.ID, txn.Timestamp, transactionData)
 	if err != nil {
+		// Ignore duplicate transactions and return success response
+		if err.(*pq.Error).Code.Name() == "unique_violation" {
+			log.Println("Ignoring duplicate transaction of id:", txn.ID)
+			err = tx.Rollback()
+			if err != nil {
+				log.Println("Error rolling back transaction:", err)
+			}
+			return true
+		}
 		return handleTransactionError(tx, errors.Wrap(err, "insert transaction failed"))
 	}
 

models/transactions_test.go

@@ -4,6 +4,7 @@ import (
 	"database/sql"
 	"log"
 	"os"
+	"sync"
 	"testing"
 
 	_ "github.com/lib/pq"
@@ -168,9 +169,40 @@ func (ts *TransactionsModelSuite) TestTransact() {
 	exists, err := transactionDB.IsExists("t003")
 	assert.Equal(t, err, nil, "Error while checking for existing transaction")
 	assert.Equal(t, exists, true, "Transaction should exist")
+}
+
+func (ts *TransactionsModelSuite) TestDuplicateTransactions() {
+	t := ts.T()
 
-	done = transactionDB.Transact(transaction)
-	assert.Equal(t, done, false, "Transaction should not be created")
+	transactionDB := NewTransactionDB(ts.db)
+	transaction := &Transaction{
+		ID: "t005",
+		Lines: []*TransactionLine{
+			&TransactionLine{
+				AccountID: "a1",
+				Delta:     100,
+			},
+			&TransactionLine{
+				AccountID: "a2",
+				Delta:     -100,
+			},
+		},
+	}
+
+	var wg sync.WaitGroup
+	wg.Add(5)
+	for i := 1; i <= 5; i++ {
+		go func(txn *Transaction) {
+			done := transactionDB.Transact(transaction)
+			assert.Equal(t, done, true, "Transaction creation should be success")
+			wg.Done()
+		}(transaction)
+	}
+	wg.Wait()
+
+	exists, err := transactionDB.IsExists("t005")
+	assert.Equal(t, err, nil, "Error while checking for existing transaction")
+	assert.Equal(t, exists, true, "Transaction should exist")
 }
 
 func (ts *TransactionsModelSuite) TestTransactWithBoundaryValues() {

tests/transactions_test.go

@@ -93,8 +93,8 @@ func RunCSVTests(accountsEndpoint string, transactionsEndpoint string, filename
 				localwg.Done()
 			}()
 			localwg.Wait()
-			if status1 == http.StatusCreated && status2 == http.StatusCreated {
-				log.Fatalf("Parallel repeated transactions with same ID %v are accepted", t["id"])
+			if (status1 != http.StatusCreated && status1 != http.StatusAccepted) || (status2 != http.StatusCreated && status2 != http.StatusAccepted) {
+				log.Fatalf("Parallel repeated transactions with same ID %v are not accepted", t["id"])
 			} else if status1 >= 400 && status2 >= 400 {
 				log.Fatalf("Both parallel repeated transactions with same ID %v are failed", t["id"])
 			}