Add minPriceUSD in L2DB, check maxTxs atomically

- Add config parameter `Coordinator.L2DB.MinPriceUSD` which allows rejecting txs to the pool that have a fee lower than the minimum. - In pool tx insertion, checking the number of pending txs atomically with the insertion to avoid data races leading to more than MaxTxs pending txs in the pool.
2026-02-06 19:06:42 +01:00 · 2021-02-22 16:37:18 +01:00
parent df0cc32eed
commit 3706ddb2fb
17 changed files with 271 additions and 127 deletions
--- a/api/api_test.go
+++ b/api/api_test.go
@@ -221,7 +221,7 @@ func TestMain(m *testing.M) {
 		panic(err)
 	}
 	// L2DB
-	l2DB := l2db.NewL2DB(database, 10, 1000, 24*time.Hour, apiConnCon)
+	l2DB := l2db.NewL2DB(database, 10, 1000, 0.0, 24*time.Hour, apiConnCon)
 	test.WipeDB(l2DB.DB()) // this will clean HistoryDB and L2DB
 	// Config (smart contract constants)
 	chainID := uint16(0)
@@ -585,7 +585,7 @@ func TestTimeout(t *testing.T) {
 	hdbTO := historydb.NewHistoryDB(databaseTO, apiConnConTO)
 	require.NoError(t, err)
 	// L2DB
-	l2DBTO := l2db.NewL2DB(databaseTO, 10, 1000, 24*time.Hour, apiConnConTO)
+	l2DBTO := l2db.NewL2DB(databaseTO, 10, 1000, 0.0, 24*time.Hour, apiConnConTO)

 	// API
 	apiGinTO := gin.Default()
--- a/api/txspool.go
+++ b/api/txspool.go
@@ -2,6 +2,7 @@ package api

 import (
 	"errors"
+	"fmt"
 	"math/big"
 	"net/http"

@@ -180,6 +181,11 @@ func (a *API) verifyPoolL2TxWrite(txw *l2db.PoolL2TxWrite) error {
 	if err != nil {
 		return tracerr.Wrap(err)
 	}
+	// Validate TokenID
+	if poolTx.TokenID != account.TokenID {
+		return tracerr.Wrap(fmt.Errorf("tx.TokenID (%v) != account.TokenID (%v)",
+			poolTx.TokenID, account.TokenID))
+	}
 	// Check signature
 	if !poolTx.VerifySignature(a.chainID, account.BJJ) {
 		return tracerr.Wrap(errors.New("wrong signature"))
--- a/api/txspool_test.go
+++ b/api/txspool_test.go
@@ -10,6 +10,7 @@ import (
 	"github.com/hermeznetwork/hermez-node/db/historydb"
 	"github.com/iden3/go-iden3-crypto/babyjub"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )

 // testPoolTxReceive is a struct to be used to assert the response
@@ -170,9 +171,9 @@ func TestPoolTxs(t *testing.T) {
 	fetchedTxID := common.TxID{}
 	for _, tx := range tc.poolTxsToSend {
 		jsonTxBytes, err := json.Marshal(tx)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		jsonTxReader := bytes.NewReader(jsonTxBytes)
-		assert.NoError(
+		require.NoError(
 			t, doGoodReq(
 				"POST",
 				endpoint,
@@ -187,42 +188,42 @@ func TestPoolTxs(t *testing.T) {
 	badTx.Amount = "99950000000000000"
 	badTx.Fee = 255
 	jsonTxBytes, err := json.Marshal(badTx)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	jsonTxReader := bytes.NewReader(jsonTxBytes)
 	err = doBadReq("POST", endpoint, jsonTxReader, 400)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// Wrong signature
 	badTx = tc.poolTxsToSend[0]
 	badTx.FromIdx = "hez:foo:1000"
 	jsonTxBytes, err = json.Marshal(badTx)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	jsonTxReader = bytes.NewReader(jsonTxBytes)
 	err = doBadReq("POST", endpoint, jsonTxReader, 400)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// Wrong to
 	badTx = tc.poolTxsToSend[0]
 	ethAddr := "hez:0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"
 	badTx.ToEthAddr = &ethAddr
 	badTx.ToIdx = nil
 	jsonTxBytes, err = json.Marshal(badTx)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	jsonTxReader = bytes.NewReader(jsonTxBytes)
 	err = doBadReq("POST", endpoint, jsonTxReader, 400)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// Wrong rq
 	badTx = tc.poolTxsToSend[0]
 	rqFromIdx := "hez:foo:30"
 	badTx.RqFromIdx = &rqFromIdx
 	jsonTxBytes, err = json.Marshal(badTx)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	jsonTxReader = bytes.NewReader(jsonTxBytes)
 	err = doBadReq("POST", endpoint, jsonTxReader, 400)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// GET
 	endpoint += "/"
 	for _, tx := range tc.poolTxsToReceive {
 		fetchedTx := testPoolTxReceive{}
-		assert.NoError(
+		require.NoError(
 			t, doGoodReq(
 				"GET",
 				endpoint+tx.TxID.String(),
@@ -233,10 +234,10 @@ func TestPoolTxs(t *testing.T) {
 	}
 	// 400, due invalid TxID
 	err = doBadReq("GET", endpoint+"0xG2241b6f2b1dd772dba391f4a1a3407c7c21f598d86e2585a14e616fb4a255f823", nil, 400)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// 404, due inexistent TxID in DB
 	err = doBadReq("GET", endpoint+"0x02241b6f2b1dd772dba391f4a1a3407c7c21f598d86e2585a14e616fb4a255f823", nil, 404)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 }

 func assertPoolTx(t *testing.T, expected, actual testPoolTxReceive) {
--- a/cli/node/cfg.buidler.toml
+++ b/cli/node/cfg.buidler.toml
@@ -67,6 +67,7 @@ BJJ = "0x1b176232f78ba0d388ecc5f4896eca2d3b3d4f272092469f559247297f5c0c13"
 [Coordinator.L2DB]
 SafetyPeriod = 10
 MaxTxs       = 512
+MinFeeUSD    = 0.0
 TTL          = "24h"
 PurgeBatchDelay = 10
 InvalidateBatchDelay = 20
--- a/cli/node/main.go
+++ b/cli/node/main.go
@@ -173,6 +173,7 @@ func cmdDiscard(c *cli.Context) error {
 		db,
 		cfg.Coordinator.L2DB.SafetyPeriod,
 		cfg.Coordinator.L2DB.MaxTxs,
+		cfg.Coordinator.L2DB.MinFeeUSD,
 		cfg.Coordinator.L2DB.TTL.Duration,
 		nil,
 	)
--- a/common/utils.go
+++ b/common/utils.go
@@ -62,3 +62,17 @@ func RmEndingZeroes(siblings []*merkletree.Hash) []*merkletree.Hash {
 	}
 	return siblings[:pos]
 }
+
+// TokensToUSD is a helper function to calculate the USD value of a certain
+// amount of tokens considering the normalized token price (which is the price
+// commonly reported by exhanges)
+func TokensToUSD(amount *big.Int, decimals uint64, valueUSD float64) float64 {
+	amountF := new(big.Float).SetInt(amount)
+	// Divide by 10^decimals to normalize the amount
+	baseF := new(big.Float).SetInt(new(big.Int).Exp(
+		big.NewInt(10), big.NewInt(int64(decimals)), nil)) //nolint:gomnd
+	amountF.Mul(amountF, big.NewFloat(valueUSD))
+	amountF.Quo(amountF, baseF)
+	amountUSD, _ := amountF.Float64()
+	return amountUSD
+}
--- a/config/config.go
+++ b/config/config.go
@@ -105,6 +105,10 @@ type Coordinator struct {
 		// reached, inserts to the pool will be denied until some of
 		// the pending txs are forged.
 		MaxTxs uint32 `validate:"required"`
+		// MinFeeUSD is the minimum fee in USD that a tx must pay in
+		// order to be accepted into the pool.  Txs with lower than
+		// minimum fee will be rejected at the API level.
+		MinFeeUSD float64
 		// TTL is the Time To Live for L2Txs in the pool.  Once MaxTxs
 		// L2Txs is reached, L2Txs older than TTL will be deleted.
 		TTL Duration `validate:"required"`
--- a/coordinator/coordinator_test.go
+++ b/coordinator/coordinator_test.go
@@ -105,7 +105,7 @@ func newTestModules(t *testing.T) modules {
 	db, err := dbUtils.InitSQLDB(5432, "localhost", "hermez", pass, "hermez")
 	require.NoError(t, err)
 	test.WipeDB(db)
-	l2DB := l2db.NewL2DB(db, 10, 100, 24*time.Hour, nil)
+	l2DB := l2db.NewL2DB(db, 10, 100, 0.0, 24*time.Hour, nil)
 	historyDB := historydb.NewHistoryDB(db, nil)

 	txSelDBPath, err = ioutil.TempDir("", "tmpTxSelDB")
--- a/coordinator/purger_test.go
+++ b/coordinator/purger_test.go
@@ -21,7 +21,7 @@ func newL2DB(t *testing.T) *l2db.L2DB {
 	db, err := dbUtils.InitSQLDB(5432, "localhost", "hermez", pass, "hermez")
 	require.NoError(t, err)
 	test.WipeDB(db)
-	return l2db.NewL2DB(db, 10, 100, 24*time.Hour, nil)
+	return l2db.NewL2DB(db, 10, 100, 0.0, 24*time.Hour, nil)
 }

 func newStateDB(t *testing.T) *statedb.LocalStateDB {
--- a/db/historydb/historydb.go
+++ b/db/historydb/historydb.go
@@ -447,7 +447,8 @@ func (hdb *HistoryDB) addTokens(d meddler.DB, tokens []common.Token) error {
 	))
 }

-// UpdateTokenValue updates the USD value of a token
+// UpdateTokenValue updates the USD value of a token.  Value is the price in
+// USD of a normalized token (1 token = 10^decimals units)
 func (hdb *HistoryDB) UpdateTokenValue(tokenSymbol string, value float64) error {
 	// Sanitize symbol
 	tokenSymbol = strings.ToValidUTF8(tokenSymbol, " ")
--- a/db/l2db/apiqueries.go
+++ b/db/l2db/apiqueries.go
@@ -1,12 +1,18 @@
 package l2db

 import (
+	"fmt"
+
 	ethCommon "github.com/ethereum/go-ethereum/common"
 	"github.com/hermeznetwork/hermez-node/common"
 	"github.com/hermeznetwork/tracerr"
 	"github.com/russross/meddler"
 )

+var (
+	errPoolFull = fmt.Errorf("the pool is at full capacity. More transactions are not accepted currently")
+)
+
 // AddAccountCreationAuthAPI inserts an account creation authorization into the DB
 func (l2db *L2DB) AddAccountCreationAuthAPI(auth *common.AccountCreationAuth) error {
 	cancel, err := l2db.apiConnCon.Acquire()
@@ -42,20 +48,54 @@ func (l2db *L2DB) AddTxAPI(tx *PoolL2TxWrite) error {
 		return tracerr.Wrap(err)
 	}
 	defer l2db.apiConnCon.Release()
-	row := l2db.db.QueryRow(
-		"SELECT COUNT(*) FROM tx_pool WHERE state = $1;",
-		common.PoolL2TxStatePending,
-	)
-	var totalTxs uint32
-	if err := row.Scan(&totalTxs); err != nil {
+
+	row := l2db.db.QueryRow(`SELECT
+		($1::NUMERIC * token.usd * fee_percentage($2::NUMERIC)) /
+			(10.0 ^ token.decimals::NUMERIC)
+		FROM token WHERE token.token_id = $3;`,
+		tx.AmountFloat, tx.Fee, tx.TokenID)
+	var feeUSD float64
+	if err := row.Scan(&feeUSD); err != nil {
 		return tracerr.Wrap(err)
 	}
-	if totalTxs >= l2db.maxTxs {
-		return tracerr.New(
-			"The pool is at full capacity. More transactions are not accepted currently",
-		)
+	if feeUSD < l2db.minFeeUSD {
+		return tracerr.Wrap(fmt.Errorf("tx.feeUSD (%v) < minFeeUSD (%v)",
+			feeUSD, l2db.minFeeUSD))
 	}
-	return tracerr.Wrap(meddler.Insert(l2db.db, "tx_pool", tx))
+
+	// Prepare insert SQL query argument parameters
+	namesPart, err := meddler.Default.ColumnsQuoted(tx, false)
+	if err != nil {
+		return err
+	}
+	valuesPart, err := meddler.Default.PlaceholdersString(tx, false)
+	if err != nil {
+		return err
+	}
+	values, err := meddler.Default.Values(tx, false)
+	if err != nil {
+		return err
+	}
+
+	q := fmt.Sprintf(
+		`INSERT INTO tx_pool (%s)
+		SELECT %s
+		WHERE (SELECT COUNT(*) FROM tx_pool WHERE state = $%v) < $%v;`,
+		namesPart, valuesPart,
+		len(values)+1, len(values)+2) //nolint:gomnd
+	values = append(values, common.PoolL2TxStatePending, l2db.maxTxs)
+	res, err := l2db.db.Exec(q, values...)
+	if err != nil {
+		return tracerr.Wrap(err)
+	}
+	rowsAffected, err := res.RowsAffected()
+	if err != nil {
+		return tracerr.Wrap(err)
+	}
+	if rowsAffected == 0 {
+		return tracerr.Wrap(errPoolFull)
+	}
+	return nil
 }

 // selectPoolTxAPI select part of queries to get PoolL2TxRead
--- a/db/l2db/l2db.go
+++ b/db/l2db/l2db.go
@@ -25,6 +25,7 @@ type L2DB struct {
 	safetyPeriod common.BatchNum
 	ttl          time.Duration
 	maxTxs       uint32 // limit of txs that are accepted in the pool
+	minFeeUSD    float64
 	apiConnCon   *db.APIConnectionController
 }

@@ -35,6 +36,7 @@ func NewL2DB(
 	db *sqlx.DB,
 	safetyPeriod common.BatchNum,
 	maxTxs uint32,
+	minFeeUSD float64,
 	TTL time.Duration,
 	apiConnCon *db.APIConnectionController,
 ) *L2DB {
@@ -43,6 +45,7 @@ func NewL2DB(
 		safetyPeriod: safetyPeriod,
 		ttl:          TTL,
 		maxTxs:       maxTxs,
+		minFeeUSD:    minFeeUSD,
 		apiConnCon:   apiConnCon,
 	}
 }
@@ -104,9 +107,8 @@ func (l2db *L2DB) UpdateTxsInfo(txs []common.PoolL2Tx) error {
 	return nil
 }

-// AddTxTest inserts a tx into the L2DB. This is useful for test purposes,
-// but in production txs will only be inserted through the API
-func (l2db *L2DB) AddTxTest(tx *common.PoolL2Tx) error {
+// NewPoolL2TxWriteFromPoolL2Tx creates a new PoolL2TxWrite from a PoolL2Tx
+func NewPoolL2TxWriteFromPoolL2Tx(tx *common.PoolL2Tx) *PoolL2TxWrite {
 	// transform tx from *common.PoolL2Tx to PoolL2TxWrite
 	insertTx := &PoolL2TxWrite{
 		TxID:      tx.TxID,
@@ -148,6 +150,13 @@ func (l2db *L2DB) AddTxTest(tx *common.PoolL2Tx) error {
 	f := new(big.Float).SetInt(tx.Amount)
 	amountF, _ := f.Float64()
 	insertTx.AmountFloat = amountF
+	return insertTx
+}
+
+// AddTxTest inserts a tx into the L2DB. This is useful for test purposes,
+// but in production txs will only be inserted through the API
+func (l2db *L2DB) AddTxTest(tx *common.PoolL2Tx) error {
+	insertTx := NewPoolL2TxWriteFromPoolL2Tx(tx)
 	// insert tx
 	return tracerr.Wrap(meddler.Insert(l2db.db, "tx_pool", insertTx))
 }
@@ -158,7 +167,8 @@ tx_pool.to_bjj, tx_pool.token_id, tx_pool.amount, tx_pool.fee, tx_pool.nonce,
 tx_pool.state, tx_pool.info, tx_pool.signature, tx_pool.timestamp, rq_from_idx, 
 rq_to_idx, tx_pool.rq_to_eth_addr, tx_pool.rq_to_bjj, tx_pool.rq_token_id, tx_pool.rq_amount, 
 tx_pool.rq_fee, tx_pool.rq_nonce, tx_pool.tx_type, 
-fee_percentage(tx_pool.fee::NUMERIC) * token.usd * tx_pool.amount_f AS fee_usd, token.usd_update  
+(fee_percentage(tx_pool.fee::NUMERIC) * token.usd * tx_pool.amount_f) /
+	(10.0 ^ token.decimals::NUMERIC) AS fee_usd, token.usd_update
 FROM tx_pool INNER JOIN token ON tx_pool.token_id = token.token_id `

 // GetTx  return the specified Tx in common.PoolL2Tx format
--- a/db/l2db/l2db_test.go
+++ b/db/l2db/l2db_test.go
@@ -2,8 +2,7 @@ package l2db

 import (
 	"database/sql"
-	"math"
-	"math/big"
+	"fmt"
 	"os"
 	"testing"
 	"time"
@@ -21,12 +20,14 @@ import (
 	"github.com/stretchr/testify/require"
 )

+var decimals = uint64(3)
+var tokenValue = 1.0 // The price update gives a value of 1.0 USD to the token
 var l2DB *L2DB
 var l2DBWithACC *L2DB
 var historyDB *historydb.HistoryDB
 var tc *til.Context
 var tokens map[common.TokenID]historydb.TokenWithUSD
-var tokensValue map[common.TokenID]float64
+
 var accs map[common.Idx]common.Account

 func TestMain(m *testing.M) {
@@ -36,9 +37,9 @@ func TestMain(m *testing.M) {
 	if err != nil {
 		panic(err)
 	}
-	l2DB = NewL2DB(db, 10, 1000, 24*time.Hour, nil)
+	l2DB = NewL2DB(db, 10, 1000, 0.0, 24*time.Hour, nil)
 	apiConnCon := dbUtils.NewAPICnnectionController(1, time.Second)
-	l2DBWithACC = NewL2DB(db, 10, 1000, 24*time.Hour, apiConnCon)
+	l2DBWithACC = NewL2DB(db, 10, 1000, 0.0, 24*time.Hour, apiConnCon)
 	test.WipeDB(l2DB.DB())
 	historyDB = historydb.NewHistoryDB(db, nil)
 	// Run tests
@@ -59,10 +60,10 @@ func prepareHistoryDB(historyDB *historydb.HistoryDB) error {

 			AddToken(1)
 			AddToken(2)
-			CreateAccountDeposit(1) A: 2000
-			CreateAccountDeposit(2) A: 2000
-			CreateAccountDeposit(1) B: 1000
-			CreateAccountDeposit(2) B: 1000
+			CreateAccountDeposit(1) A: 20000
+			CreateAccountDeposit(2) A: 20000
+			CreateAccountDeposit(1) B: 10000
+			CreateAccountDeposit(2) B: 10000
 			> batchL1 
 			> batchL1
 			> block
@@ -83,15 +84,23 @@ func prepareHistoryDB(historyDB *historydb.HistoryDB) error {
 	if err != nil {
 		return tracerr.Wrap(err)
 	}
+	for i := range blocks {
+		block := &blocks[i]
+		for j := range block.Rollup.AddedTokens {
+			token := &block.Rollup.AddedTokens[j]
+			token.Name = fmt.Sprintf("Token %d", token.TokenID)
+			token.Symbol = fmt.Sprintf("TK%d", token.TokenID)
+			token.Decimals = decimals
+		}
+	}
+
 	tokens = make(map[common.TokenID]historydb.TokenWithUSD)
-	tokensValue = make(map[common.TokenID]float64)
+	// tokensValue = make(map[common.TokenID]float64)
 	accs = make(map[common.Idx]common.Account)
-	value := 5 * 5.389329
 	now := time.Now().UTC()
 	// Add all blocks except for the last one
 	for i := range blocks[:len(blocks)-1] {
-		err = historyDB.AddBlockSCData(&blocks[i])
-		if err != nil {
+		if err := historyDB.AddBlockSCData(&blocks[i]); err != nil {
 			return tracerr.Wrap(err)
 		}
 		for _, batch := range blocks[i].Rollup.Batches {
@@ -107,39 +116,38 @@ func prepareHistoryDB(historyDB *historydb.HistoryDB) error {
 				Name:        token.Name,
 				Symbol:      token.Symbol,
 				Decimals:    token.Decimals,
+				USD:         &tokenValue,
+				USDUpdate:   &now,
 			}
-			tokensValue[token.TokenID] = value / math.Pow(10, float64(token.Decimals))
-			readToken.USDUpdate = &now
-			readToken.USD = &value
 			tokens[token.TokenID] = readToken
-		}
-		// Set value to the tokens (tokens have no symbol)
-		tokenSymbol := ""
-		err := historyDB.UpdateTokenValue(tokenSymbol, value)
-		if err != nil {
-			return tracerr.Wrap(err)
+			// Set value to the tokens
+			err := historyDB.UpdateTokenValue(readToken.Symbol, *readToken.USD)
+			if err != nil {
+				return tracerr.Wrap(err)
+			}
 		}
 	}
 	return nil
 }

 func generatePoolL2Txs() ([]common.PoolL2Tx, error) {
+	// Fee = 126 corresponds to ~10%
 	setPool := `
 			Type: PoolL2
-			PoolTransfer(1) A-B: 6 (4)
-			PoolTransfer(2) A-B: 3 (1)
-			PoolTransfer(1) B-A: 5 (2)
-			PoolTransfer(2) B-A: 10 (3)
-			PoolTransfer(1) A-B: 7 (2)
-			PoolTransfer(2) A-B: 2 (1)
-			PoolTransfer(1) B-A: 8 (2)
-			PoolTransfer(2) B-A: 1 (1)
-			PoolTransfer(1) A-B: 3 (1)
-			PoolTransferToEthAddr(2) B-A: 5 (2)
-			PoolTransferToBJJ(2) B-A: 5 (2)
+			PoolTransfer(1) A-B: 6000 (126)
+			PoolTransfer(2) A-B: 3000 (126)
+			PoolTransfer(1) B-A: 5000 (126)
+			PoolTransfer(2) B-A: 10000 (126)
+			PoolTransfer(1) A-B: 7000 (126)
+			PoolTransfer(2) A-B: 2000 (126)
+			PoolTransfer(1) B-A: 8000 (126)
+			PoolTransfer(2) B-A: 1000 (126)
+			PoolTransfer(1) A-B: 3000 (126)
+			PoolTransferToEthAddr(2) B-A: 5000 (126)
+			PoolTransferToBJJ(2) B-A: 5000 (126)

-			PoolExit(1) A: 5 (2)
-			PoolExit(2) B: 3 (1)
+			PoolExit(1) A: 5000 (126)
+			PoolExit(2) B: 3000 (126)
 		`
 	poolL2Txs, err := tc.GeneratePoolL2Txs(setPool)
 	if err != nil {
@@ -154,25 +162,74 @@ func TestAddTxTest(t *testing.T) {
 		log.Error("Error prepare historyDB", err)
 	}
 	poolL2Txs, err := generatePoolL2Txs()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	for i := range poolL2Txs {
 		err := l2DB.AddTxTest(&poolL2Txs[i])
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		fetchedTx, err := l2DB.GetTx(poolL2Txs[i].TxID)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		assertTx(t, &poolL2Txs[i], fetchedTx)
 		nameZone, offset := fetchedTx.Timestamp.Zone()
 		assert.Equal(t, "UTC", nameZone)
 		assert.Equal(t, 0, offset)
 	}
 }
+
+func TestAddTxAPI(t *testing.T) {
+	err := prepareHistoryDB(historyDB)
+	if err != nil {
+		log.Error("Error prepare historyDB", err)
+	}
+
+	oldMaxTxs := l2DBWithACC.maxTxs
+	// set max number of pending txs that can be kept in the pool to 5
+	l2DBWithACC.maxTxs = 5
+
+	poolL2Txs, err := generatePoolL2Txs()
+	txs := make([]*PoolL2TxWrite, len(poolL2Txs))
+	for i := range poolL2Txs {
+		txs[i] = NewPoolL2TxWriteFromPoolL2Tx(&poolL2Txs[i])
+	}
+	require.NoError(t, err)
+	require.GreaterOrEqual(t, len(poolL2Txs), 8)
+	for i := range txs[:5] {
+		err := l2DBWithACC.AddTxAPI(txs[i])
+		require.NoError(t, err)
+		fetchedTx, err := l2DB.GetTx(poolL2Txs[i].TxID)
+		require.NoError(t, err)
+		assertTx(t, &poolL2Txs[i], fetchedTx)
+		nameZone, offset := fetchedTx.Timestamp.Zone()
+		assert.Equal(t, "UTC", nameZone)
+		assert.Equal(t, 0, offset)
+	}
+	err = l2DBWithACC.AddTxAPI(txs[5])
+	assert.Equal(t, errPoolFull, tracerr.Unwrap(err))
+	// reset maxTxs to original value
+	l2DBWithACC.maxTxs = oldMaxTxs
+
+	// set minFeeUSD to a high value than the tx feeUSD to test the error
+	// of inserting a tx with lower than min fee
+	oldMinFeeUSD := l2DBWithACC.minFeeUSD
+	tx := txs[5]
+	feeAmount, err := common.CalcFeeAmount(tx.Amount, tx.Fee)
+	require.NoError(t, err)
+	feeAmountUSD := common.TokensToUSD(feeAmount, decimals, tokenValue)
+	// set minFeeUSD higher than the tx fee to trigger the error
+	l2DBWithACC.minFeeUSD = feeAmountUSD + 1
+	err = l2DBWithACC.AddTxAPI(tx)
+	require.Error(t, err)
+	assert.Regexp(t, "tx.feeUSD (.*) < minFeeUSD (.*)", err.Error())
+	// reset minFeeUSD to original value
+	l2DBWithACC.minFeeUSD = oldMinFeeUSD
+}
+
 func TestUpdateTxsInfo(t *testing.T) {
 	err := prepareHistoryDB(historyDB)
 	if err != nil {
 		log.Error("Error prepare historyDB", err)
 	}
 	poolL2Txs, err := generatePoolL2Txs()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	for i := range poolL2Txs {
 		err := l2DB.AddTxTest(&poolL2Txs[i])
 		require.NoError(t, err)
@@ -186,7 +243,7 @@ func TestUpdateTxsInfo(t *testing.T) {

 	for i := range poolL2Txs {
 		fetchedTx, err := l2DB.GetTx(poolL2Txs[i].TxID)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		assert.Equal(t, "test", fetchedTx.Info)
 	}
 }
@@ -204,9 +261,8 @@ func assertTx(t *testing.T, expected, actual *common.PoolL2Tx) {
 		assert.Less(t, token.USDUpdate.Unix()-3, actual.AbsoluteFeeUpdate.Unix())
 		expected.AbsoluteFeeUpdate = actual.AbsoluteFeeUpdate
 		// Set expected fee
-		f := new(big.Float).SetInt(expected.Amount)
-		amountF, _ := f.Float64()
-		expected.AbsoluteFee = *token.USD * amountF * expected.Fee.Percentage()
+		amountUSD := common.TokensToUSD(expected.Amount, token.Decimals, *token.USD)
+		expected.AbsoluteFee = amountUSD * expected.Fee.Percentage()
 		test.AssertUSD(t, &expected.AbsoluteFee, &actual.AbsoluteFee)
 	}
 	assert.Equal(t, expected, actual)
@@ -231,19 +287,28 @@ func TestGetPending(t *testing.T) {
 		log.Error("Error prepare historyDB", err)
 	}
 	poolL2Txs, err := generatePoolL2Txs()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	var pendingTxs []*common.PoolL2Tx
 	for i := range poolL2Txs {
 		err := l2DB.AddTxTest(&poolL2Txs[i])
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		pendingTxs = append(pendingTxs, &poolL2Txs[i])
 	}
 	fetchedTxs, err := l2DB.GetPendingTxs()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	assert.Equal(t, len(pendingTxs), len(fetchedTxs))
 	for i := range fetchedTxs {
 		assertTx(t, pendingTxs[i], &fetchedTxs[i])
 	}
+	// Check AbsoluteFee amount
+	for i := range fetchedTxs {
+		tx := &fetchedTxs[i]
+		feeAmount, err := common.CalcFeeAmount(tx.Amount, tx.Fee)
+		require.NoError(t, err)
+		feeAmountUSD := common.TokensToUSD(feeAmount,
+			tokens[tx.TokenID].Decimals, *tokens[tx.TokenID].USD)
+		assert.InEpsilon(t, feeAmountUSD, tx.AbsoluteFee, 0.01)
+	}
 }

 func TestStartForging(t *testing.T) {
@@ -254,13 +319,13 @@ func TestStartForging(t *testing.T) {
 		log.Error("Error prepare historyDB", err)
 	}
 	poolL2Txs, err := generatePoolL2Txs()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	var startForgingTxIDs []common.TxID
 	randomizer := 0
 	// Add txs to DB
 	for i := range poolL2Txs {
 		err := l2DB.AddTxTest(&poolL2Txs[i])
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		if poolL2Txs[i].State == common.PoolL2TxStatePending && randomizer%2 == 0 {
 			startForgingTxIDs = append(startForgingTxIDs, poolL2Txs[i].TxID)
 		}
@@ -268,11 +333,11 @@ func TestStartForging(t *testing.T) {
 	}
 	// Start forging txs
 	err = l2DB.StartForging(startForgingTxIDs, fakeBatchNum)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// Fetch txs and check that they've been updated correctly
 	for _, id := range startForgingTxIDs {
 		fetchedTx, err := l2DBWithACC.GetTxAPI(id)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		assert.Equal(t, common.PoolL2TxStateForging, fetchedTx.State)
 		assert.Equal(t, &fakeBatchNum, fetchedTx.BatchNum)
 	}
@@ -286,13 +351,13 @@ func TestDoneForging(t *testing.T) {
 		log.Error("Error prepare historyDB", err)
 	}
 	poolL2Txs, err := generatePoolL2Txs()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	var startForgingTxIDs []common.TxID
 	randomizer := 0
 	// Add txs to DB
 	for i := range poolL2Txs {
 		err := l2DB.AddTxTest(&poolL2Txs[i])
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		if poolL2Txs[i].State == common.PoolL2TxStatePending && randomizer%2 == 0 {
 			startForgingTxIDs = append(startForgingTxIDs, poolL2Txs[i].TxID)
 		}
@@ -300,7 +365,7 @@ func TestDoneForging(t *testing.T) {
 	}
 	// Start forging txs
 	err = l2DB.StartForging(startForgingTxIDs, fakeBatchNum)
-	assert.NoError(t, err)
+	require.NoError(t, err)

 	var doneForgingTxIDs []common.TxID
 	randomizer = 0
@@ -312,12 +377,12 @@ func TestDoneForging(t *testing.T) {
 	}
 	// Done forging txs
 	err = l2DB.DoneForging(doneForgingTxIDs, fakeBatchNum)
-	assert.NoError(t, err)
+	require.NoError(t, err)

 	// Fetch txs and check that they've been updated correctly
 	for _, id := range doneForgingTxIDs {
 		fetchedTx, err := l2DBWithACC.GetTxAPI(id)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		assert.Equal(t, common.PoolL2TxStateForged, fetchedTx.State)
 		assert.Equal(t, &fakeBatchNum, fetchedTx.BatchNum)
 	}
@@ -331,13 +396,13 @@ func TestInvalidate(t *testing.T) {
 		log.Error("Error prepare historyDB", err)
 	}
 	poolL2Txs, err := generatePoolL2Txs()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	var invalidTxIDs []common.TxID
 	randomizer := 0
 	// Add txs to DB
 	for i := range poolL2Txs {
 		err := l2DB.AddTxTest(&poolL2Txs[i])
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		if poolL2Txs[i].State != common.PoolL2TxStateInvalid && randomizer%2 == 0 {
 			randomizer++
 			invalidTxIDs = append(invalidTxIDs, poolL2Txs[i].TxID)
@@ -345,11 +410,11 @@ func TestInvalidate(t *testing.T) {
 	}
 	// Invalidate txs
 	err = l2DB.InvalidateTxs(invalidTxIDs, fakeBatchNum)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// Fetch txs and check that they've been updated correctly
 	for _, id := range invalidTxIDs {
 		fetchedTx, err := l2DBWithACC.GetTxAPI(id)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		assert.Equal(t, common.PoolL2TxStateInvalid, fetchedTx.State)
 		assert.Equal(t, &fakeBatchNum, fetchedTx.BatchNum)
 	}
@@ -363,7 +428,7 @@ func TestInvalidateOldNonces(t *testing.T) {
 		log.Error("Error prepare historyDB", err)
 	}
 	poolL2Txs, err := generatePoolL2Txs()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// Update Accounts currentNonce
 	var updateAccounts []common.IdxNonce
 	var currentNonce = common.Nonce(1)
@@ -380,13 +445,13 @@ func TestInvalidateOldNonces(t *testing.T) {
 			invalidTxIDs = append(invalidTxIDs, poolL2Txs[i].TxID)
 		}
 		err := l2DB.AddTxTest(&poolL2Txs[i])
-		assert.NoError(t, err)
+		require.NoError(t, err)
 	}
 	// sanity check
 	require.Greater(t, len(invalidTxIDs), 0)

 	err = l2DB.InvalidateOldNonces(updateAccounts, fakeBatchNum)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// Fetch txs and check that they've been updated correctly
 	for _, id := range invalidTxIDs {
 		fetchedTx, err := l2DBWithACC.GetTxAPI(id)
@@ -408,7 +473,7 @@ func TestReorg(t *testing.T) {
 		log.Error("Error prepare historyDB", err)
 	}
 	poolL2Txs, err := generatePoolL2Txs()
-	assert.NoError(t, err)
+	require.NoError(t, err)

 	reorgedTxIDs := []common.TxID{}
 	nonReorgedTxIDs := []common.TxID{}
@@ -419,7 +484,7 @@ func TestReorg(t *testing.T) {
 	// Add txs to DB
 	for i := range poolL2Txs {
 		err := l2DB.AddTxTest(&poolL2Txs[i])
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		if poolL2Txs[i].State == common.PoolL2TxStatePending && randomizer%2 == 0 {
 			startForgingTxIDs = append(startForgingTxIDs, poolL2Txs[i].TxID)
 			allTxRandomize = append(allTxRandomize, poolL2Txs[i].TxID)
@@ -431,7 +496,7 @@ func TestReorg(t *testing.T) {
 	}
 	// Start forging txs
 	err = l2DB.StartForging(startForgingTxIDs, lastValidBatch)
-	assert.NoError(t, err)
+	require.NoError(t, err)

 	var doneForgingTxIDs []common.TxID
 	randomizer = 0
@@ -456,22 +521,22 @@ func TestReorg(t *testing.T) {

 	// Invalidate txs BEFORE reorgBatch --> nonReorg
 	err = l2DB.InvalidateTxs(invalidTxIDs, lastValidBatch)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// Done forging txs in reorgBatch --> Reorg
 	err = l2DB.DoneForging(doneForgingTxIDs, reorgBatch)
-	assert.NoError(t, err)
+	require.NoError(t, err)

 	err = l2DB.Reorg(lastValidBatch)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	for _, id := range reorgedTxIDs {
 		tx, err := l2DBWithACC.GetTxAPI(id)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		assert.Nil(t, tx.BatchNum)
 		assert.Equal(t, common.PoolL2TxStatePending, tx.State)
 	}
 	for _, id := range nonReorgedTxIDs {
 		fetchedTx, err := l2DBWithACC.GetTxAPI(id)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		assert.Equal(t, lastValidBatch, *fetchedTx.BatchNum)
 	}
 }
@@ -488,7 +553,7 @@ func TestReorg2(t *testing.T) {
 		log.Error("Error prepare historyDB", err)
 	}
 	poolL2Txs, err := generatePoolL2Txs()
-	assert.NoError(t, err)
+	require.NoError(t, err)

 	reorgedTxIDs := []common.TxID{}
 	nonReorgedTxIDs := []common.TxID{}
@@ -499,7 +564,7 @@ func TestReorg2(t *testing.T) {
 	// Add txs to DB
 	for i := range poolL2Txs {
 		err := l2DB.AddTxTest(&poolL2Txs[i])
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		if poolL2Txs[i].State == common.PoolL2TxStatePending && randomizer%2 == 0 {
 			startForgingTxIDs = append(startForgingTxIDs, poolL2Txs[i].TxID)
 			allTxRandomize = append(allTxRandomize, poolL2Txs[i].TxID)
@@ -511,7 +576,7 @@ func TestReorg2(t *testing.T) {
 	}
 	// Start forging txs
 	err = l2DB.StartForging(startForgingTxIDs, lastValidBatch)
-	assert.NoError(t, err)
+	require.NoError(t, err)

 	var doneForgingTxIDs []common.TxID
 	randomizer = 0
@@ -533,22 +598,22 @@ func TestReorg2(t *testing.T) {
 	}
 	// Done forging txs BEFORE reorgBatch --> nonReorg
 	err = l2DB.DoneForging(doneForgingTxIDs, lastValidBatch)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// Invalidate txs in reorgBatch --> Reorg
 	err = l2DB.InvalidateTxs(invalidTxIDs, reorgBatch)
-	assert.NoError(t, err)
+	require.NoError(t, err)

 	err = l2DB.Reorg(lastValidBatch)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	for _, id := range reorgedTxIDs {
 		tx, err := l2DBWithACC.GetTxAPI(id)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		assert.Nil(t, tx.BatchNum)
 		assert.Equal(t, common.PoolL2TxStatePending, tx.State)
 	}
 	for _, id := range nonReorgedTxIDs {
 		fetchedTx, err := l2DBWithACC.GetTxAPI(id)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		assert.Equal(t, lastValidBatch, *fetchedTx.BatchNum)
 	}
 }
@@ -564,7 +629,7 @@ func TestPurge(t *testing.T) {
 	var poolL2Tx []common.PoolL2Tx
 	for i := 0; i < generateTx; i++ {
 		poolL2TxAux, err := generatePoolL2Txs()
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		poolL2Tx = append(poolL2Tx, poolL2TxAux...)
 	}

@@ -591,7 +656,7 @@ func TestPurge(t *testing.T) {
 			deletedIDs = append(deletedIDs, poolL2Tx[i].TxID)
 		}
 		err := l2DB.AddTxTest(&tx)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 	}
 	// Set batchNum keeped txs
 	for i := range keepedIDs {
@@ -599,17 +664,17 @@ func TestPurge(t *testing.T) {
 			"UPDATE tx_pool SET batch_num = $1 WHERE tx_id = $2;",
 			safeBatchNum, keepedIDs[i],
 		)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 	}
 	// Start forging txs and set batchNum
 	err = l2DB.StartForging(doneForgingTxIDs, toDeleteBatchNum)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// Done forging txs and set batchNum
 	err = l2DB.DoneForging(doneForgingTxIDs, toDeleteBatchNum)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// Invalidate txs and set batchNum
 	err = l2DB.InvalidateTxs(invalidTxIDs, toDeleteBatchNum)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// Update timestamp of afterTTL txs
 	deleteTimestamp := time.Unix(time.Now().UTC().Unix()-int64(l2DB.ttl.Seconds()+float64(4*time.Second)), 0)
 	for _, id := range afterTTLIDs {
@@ -618,12 +683,12 @@ func TestPurge(t *testing.T) {
 			"UPDATE tx_pool SET timestamp = $1, state = $2 WHERE tx_id = $3;",
 			deleteTimestamp, common.PoolL2TxStatePending, id,
 		)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 	}

 	// Purge txs
 	err = l2DB.Purge(safeBatchNum)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// Check results
 	for _, id := range deletedIDs {
 		_, err := l2DB.GetTx(id)
@@ -631,7 +696,7 @@ func TestPurge(t *testing.T) {
 	}
 	for _, id := range keepedIDs {
 		_, err := l2DB.GetTx(id)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 	}
 }

@@ -645,10 +710,10 @@ func TestAuth(t *testing.T) {
 	for i := 0; i < len(auths); i++ {
 		// Add to the DB
 		err := l2DB.AddAccountCreationAuth(auths[i])
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		// Fetch from DB
 		auth, err := l2DB.GetAccountCreationAuth(auths[i].EthAddr)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		// Check fetched vs generated
 		assert.Equal(t, auths[i].EthAddr, auth.EthAddr)
 		assert.Equal(t, auths[i].BJJ, auth.BJJ)
@@ -666,7 +731,7 @@ func TestAddGet(t *testing.T) {
 		log.Error("Error prepare historyDB", err)
 	}
 	poolL2Txs, err := generatePoolL2Txs()
-	assert.NoError(t, err)
+	require.NoError(t, err)

 	// We will work with only 3 txs
 	require.GreaterOrEqual(t, len(poolL2Txs), 3)
@@ -709,7 +774,7 @@ func TestPurgeByExternalDelete(t *testing.T) {
 		log.Error("Error prepare historyDB", err)
 	}
 	txs, err := generatePoolL2Txs()
-	assert.NoError(t, err)
+	require.NoError(t, err)

 	// We will work with 8 txs
 	require.GreaterOrEqual(t, len(txs), 8)
--- a/db/migrations/0001.sql
+++ b/db/migrations/0001.sql
@@ -47,7 +47,7 @@ CREATE TABLE token (
    name VARCHAR(20) NOT NULL,
    symbol VARCHAR(10) NOT NULL,
    decimals INT NOT NULL,
-    usd NUMERIC,
+    usd NUMERIC, -- value of a normalized token (1 token = 10^decimals units)
    usd_update TIMESTAMP WITHOUT TIME ZONE
 );

--- a/node/node.go
+++ b/node/node.go
@@ -205,6 +205,7 @@ func NewNode(mode Mode, cfg *config.Node) (*Node, error) {
 			db,
 			cfg.Coordinator.L2DB.SafetyPeriod,
 			cfg.Coordinator.L2DB.MaxTxs,
+			cfg.Coordinator.L2DB.MinFeeUSD,
 			cfg.Coordinator.L2DB.TTL.Duration,
 			apiConnCon,
 		)
--- a/test/zkproof/flows_test.go
+++ b/test/zkproof/flows_test.go
@@ -75,7 +75,7 @@ func initTxSelector(t *testing.T, chainID uint16, hermezContractAddr ethCommon.A
 	pass := os.Getenv("POSTGRES_PASS")
 	db, err := dbUtils.InitSQLDB(5432, "localhost", "hermez", pass, "hermez")
 	require.NoError(t, err)
-	l2DB := l2db.NewL2DB(db, 10, 100, 24*time.Hour, nil)
+	l2DB := l2db.NewL2DB(db, 10, 100, 0.0, 24*time.Hour, nil)

 	dir, err := ioutil.TempDir("", "tmpSyncDB")
 	require.NoError(t, err)
--- a/txselector/txselector_test.go
+++ b/txselector/txselector_test.go
@@ -29,7 +29,7 @@ func initTest(t *testing.T, chainID uint16, hermezContractAddr ethCommon.Address
 	pass := os.Getenv("POSTGRES_PASS")
 	db, err := dbUtils.InitSQLDB(5432, "localhost", "hermez", pass, "hermez")
 	require.NoError(t, err)
-	l2DB := l2db.NewL2DB(db, 10, 100, 24*time.Hour, nil)
+	l2DB := l2db.NewL2DB(db, 10, 100, 0.0, 24*time.Hour, nil)

 	dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)