@@ -21,6 +21,7 @@ URL = "http://localhost:8545"
 
 [Synchronizer]
 SyncLoopInterval = "1s"
+StatsRefreshPeriod = "1s"
 
     [Synchronizer.StartBlockNum]
     Rollup = 1

@@ -43,3 +43,12 @@ Outbidding uint16 `json:"outbidding" meddler:"outbidding" validate:"required"`
 	// Number of blocks at the end of a slot in which any coordinator can forge if the winner has not forged one before
 	SlotDeadline uint8 `json:"slotDeadline" meddler:"slot_deadline" validate:"required"`
 }
+
+// Copy returns a deep copy of the Variables
+func (v *AuctionVariables) Copy() *AuctionVariables {
+	vCpy := *v
+	for i := range v.DefaultSlotSetBid {
+		vCpy.DefaultSlotSetBid[i] = new(big.Int).SetBytes(v.DefaultSlotSetBid[i].Bytes())
+	}
+	return &vCpy
+}

@@ -163,3 +163,9 @@ ForgeL1L2BatchTimeout int64                         `json:"forgeL1L2BatchTimeout" meddler:"forge_l1_timeout" validate:"required"`
 	WithdrawalDelay       uint64                        `json:"withdrawalDelay" meddler:"withdrawal_delay" validate:"required"`
 	Buckets               [RollupConstNumBuckets]Bucket `json:"buckets" meddler:"buckets,json"`
 }
+
+// Copy returns a deep copy of the Variables
+func (v *RollupVariables) Copy() *RollupVariables {
+	vCpy := *v
+	return &vCpy
+}

@@ -23,3 +23,9 @@ WithdrawalDelay            uint64            `json:"withdrawalDelay" meddler:"withdrawal_delay" validate:"required"`
 	EmergencyModeStartingTime  uint64            `json:"emergencyModeStartingTime" meddler:"emergency_start_time"`
 	EmergencyMode              bool              `json:"emergencyMode" meddler:"emergency_mode"`
 }
+
+// Copy returns a deep copy of the Variables
+func (v *WDelayerVariables) Copy() *WDelayerVariables {
+	vCpy := *v
+	return &vCpy
+}

@@ -66,9 +66,10 @@ Web3 struct {
 		URL string `validate:"required"`
 	} `validate:"required"`
 	Synchronizer struct {
-		SyncLoopInterval Duration                         `validate:"required"`
-		StartBlockNum    synchronizer.ConfigStartBlockNum `validate:"required"`
-		InitialVariables synchronizer.SCVariables         `validate:"required"`
+		SyncLoopInterval   Duration                         `validate:"required"`
+		StatsRefreshPeriod Duration                         `validate:"required"`
+		StartBlockNum      synchronizer.ConfigStartBlockNum `validate:"required"`
+		InitialVariables   synchronizer.SCVariables         `validate:"required"`
 	} `validate:"required"`
 	SmartContracts struct {
 		Rollup       ethCommon.Address `validate:"required"`

@@ -172,6 +172,7 @@ RollupUpdateFeeAddToken(newFeeAddToken *big.Int) (*types.Transaction, error)
 
 	// Viewers
 	RollupRegisterTokensCount() (*big.Int, error)
+	RollupLastForgedBatch() (int64, error)
 
 	//
 	// Smart Contract Status
@@ -400,19 +401,26 @@ return tx, nil
 }
 
 // RollupRegisterTokensCount is the interface to call the smart contract function
-func (c *RollupClient) RollupRegisterTokensCount() (*big.Int, error) {
-	var registerTokensCount *big.Int
+func (c *RollupClient) RollupRegisterTokensCount() (registerTokensCount *big.Int, err error) {
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		hermez, err := Hermez.NewHermez(c.address, ec)
-		if err != nil {
-			return err
-		}
-		registerTokensCount, err = hermez.RegisterTokensCount(nil)
+		registerTokensCount, err = c.hermez.RegisterTokensCount(nil)
 		return err
 	}); err != nil {
 		return nil, err
 	}
 	return registerTokensCount, nil
+}
+
+// RollupLastForgedBatch is the interface to call the smart contract function
+func (c *RollupClient) RollupLastForgedBatch() (lastForgedBatch int64, err error) {
+	if err := c.client.Call(func(ec *ethclient.Client) error {
+		_lastForgedBatch, err := c.hermez.LastForgedBatch(nil)
+		lastForgedBatch = int64(_lastForgedBatch)
+		return err
+	}); err != nil {
+		return 0, err
+	}
+	return lastForgedBatch, nil
 }
 
 // RollupUpdateForgeL1L2BatchTimeout is the interface to call the smart contract function

@@ -114,8 +114,9 @@ return nil, err
 	}
 
 	sync, err := synchronizer.NewSynchronizer(client, historyDB, stateDB, synchronizer.Config{
-		StartBlockNum:    cfg.Synchronizer.StartBlockNum,
-		InitialVariables: cfg.Synchronizer.InitialVariables,
+		StartBlockNum:      cfg.Synchronizer.StartBlockNum,
+		InitialVariables:   cfg.Synchronizer.InitialVariables,
+		StatsRefreshPeriod: cfg.Synchronizer.StatsRefreshPeriod.Duration,
 	})
 	if err != nil {
 		return nil, err
@@ -159,9 +160,8 @@ client,
 		)
 	}
 	var debugAPI *debugapi.DebugAPI
-	println("apiaddr", cfg.Debug.APIAddress)
 	if cfg.Debug.APIAddress != "" {
-		debugAPI = debugapi.NewDebugAPI(cfg.Debug.APIAddress, stateDB)
+		debugAPI = debugapi.NewDebugAPI(cfg.Debug.APIAddress, stateDB, sync)
 	}
 	ctx, cancel := context.WithCancel(context.Background())
 	return &Node{

@@ -5,6 +5,8 @@ "context"
 	"database/sql"
 	"fmt"
 	"math/big"
+	"sync"
+	"time"
 
 	"github.com/ethereum/go-ethereum"
 	"github.com/hermeznetwork/hermez-node/common"
@@ -39,6 +41,93 @@ // 	NextForgerAddr    ethCommon.Address
 // 	Synchronized      bool
 // }
 
+// Stats of the syncrhonizer
+type Stats struct {
+	Eth struct {
+		RefreshPeriod time.Duration
+		Updated       time.Time
+		FirstBlock    int64
+		LastBlock     int64
+		LastBatch     int64
+	}
+	Sync struct {
+		Updated   time.Time
+		LastBlock int64
+		LastBatch int64
+	}
+}
+
+// StatsHolder stores stats and that allows reading and writing them
+// concurrently
+type StatsHolder struct {
+	stats Stats
+	rw    sync.RWMutex
+}
+
+// NewStatsHolder creates a new StatsHolder
+func NewStatsHolder(firstBlock int64, refreshPeriod time.Duration) *StatsHolder {
+	stats := Stats{}
+	stats.Eth.RefreshPeriod = refreshPeriod
+	stats.Eth.FirstBlock = firstBlock
+	return &StatsHolder{stats: stats}
+}
+
+// UpdateSync updates the synchronizer stats
+func (s *StatsHolder) UpdateSync(lastBlock int64, lastBatch *common.BatchNum) {
+	now := time.Now()
+	s.rw.Lock()
+	s.stats.Sync.LastBlock = lastBlock
+	if lastBatch != nil {
+		s.stats.Sync.LastBatch = int64(*lastBatch)
+	}
+	s.stats.Sync.Updated = now
+	s.rw.Unlock()
+}
+
+// UpdateEth updates the ethereum stats, only if the previous stats expired
+func (s *StatsHolder) UpdateEth(ethClient eth.ClientInterface) error {
+	now := time.Now()
+	s.rw.RLock()
+	elapsed := now.Sub(s.stats.Eth.Updated)
+	s.rw.RUnlock()
+	if elapsed < s.stats.Eth.RefreshPeriod {
+		return nil
+	}
+
+	lastBlock, err := ethClient.EthCurrentBlock()
+	if err != nil {
+		return err
+	}
+	lastBatch, err := ethClient.RollupLastForgedBatch()
+	if err != nil {
+		return err
+	}
+	s.rw.Lock()
+	s.stats.Eth.Updated = now
+	s.stats.Eth.LastBlock = lastBlock
+	s.stats.Eth.LastBatch = lastBatch
+	s.rw.Unlock()
+	return nil
+}
+
+// CopyStats returns a copy of the inner Stats
+func (s *StatsHolder) CopyStats() *Stats {
+	s.rw.RLock()
+	sCopy := s.stats
+	s.rw.RUnlock()
+	return &sCopy
+}
+
+func (s *StatsHolder) blocksPerc() float64 {
+	return float64(s.stats.Sync.LastBlock-s.stats.Eth.FirstBlock) * 100.0 /
+		float64(s.stats.Eth.LastBlock-s.stats.Eth.FirstBlock)
+}
+
+func (s *StatsHolder) batchesPerc(batchNum int64) float64 {
+	return float64(batchNum) * 100.0 /
+		float64(s.stats.Eth.LastBatch)
+}
+
 // ConfigStartBlockNum sets the first block used to start tracking the smart
 // contracts
 type ConfigStartBlockNum struct {
@@ -56,8 +145,9 @@ }
 
 // Config is the Synchronizer configuration
 type Config struct {
-	StartBlockNum    ConfigStartBlockNum
-	InitialVariables SCVariables
+	StartBlockNum      ConfigStartBlockNum
+	InitialVariables   SCVariables
+	StatsRefreshPeriod time.Duration
 }
 
 // Synchronizer implements the Synchronizer type
@@ -71,6 +161,7 @@ stateDB           *statedb.StateDB
 	cfg               Config
 	startBlockNum     int64
 	vars              SCVariables
+	stats             *StatsHolder
 	// firstSavedBlock  *common.Block
 	// mux sync.Mutex
 }
@@ -103,6 +194,7 @@ }
 	if startBlockNum < cfg.StartBlockNum.WDelayer {
 		startBlockNum = cfg.StartBlockNum.WDelayer
 	}
+	stats := NewStatsHolder(startBlockNum, cfg.StatsRefreshPeriod)
 	s := &Synchronizer{
 		ethClient:         ethClient,
 		auctionConstants:  *auctionConstants,
@@ -112,10 +204,16 @@ historyDB:         historyDB,
 		stateDB:           stateDB,
 		cfg:               cfg,
 		startBlockNum:     startBlockNum,
+		stats:             stats,
 	}
 	return s, s.init()
 }
 
+// Stats returns a copy of the Synchronizer Stats
+func (s *Synchronizer) Stats() *Stats {
+	return s.stats.CopyStats()
+}
+
 // AuctionConstants returns the AuctionConstants read from the smart contract
 func (s *Synchronizer) AuctionConstants() *common.AuctionConstants {
 	return &s.auctionConstants
@@ -133,11 +231,13 @@ }
 
 func (s *Synchronizer) init() error {
 	rollup, auction, wDelayer, err := s.historyDB.GetSCVars()
+	// If SCVars are not in the HistoryDB, this is probably the first run
+	// of the Synchronizer: store the initial vars taken from config
 	if err == sql.ErrNoRows {
 		rollup = &s.cfg.InitialVariables.Rollup
 		auction = &s.cfg.InitialVariables.Auction
 		wDelayer = &s.cfg.InitialVariables.WDelayer
-		log.Debug("Setting initial SCVars in HistoryDB")
+		log.Info("Setting initial SCVars in HistoryDB")
 		if err = s.historyDB.SetInitialSCVars(rollup, auction, wDelayer); err != nil {
 			return err
 		}
@@ -145,6 +245,47 @@ }
 	s.vars.Rollup = *rollup
 	s.vars.Auction = *auction
 	s.vars.WDelayer = *wDelayer
+
+	// Update stats parameters so that they have valid values before the
+	// first Sync call
+	if err := s.stats.UpdateEth(s.ethClient); err != nil {
+		return err
+	}
+	var lastBlockNum int64
+	lastSavedBlock, err := s.historyDB.GetLastBlock()
+	if err != nil && err != sql.ErrNoRows {
+		return err
+	}
+	// If there's no block in the DB (or we only have the default block 0),
+	// make sure that the stateDB is clean
+	if err == sql.ErrNoRows || lastSavedBlock.EthBlockNum == 0 {
+		if err := s.stateDB.Reset(0); err != nil {
+			return err
+		}
+	} else {
+		lastBlockNum = lastSavedBlock.EthBlockNum
+	}
+	lastBatchNum, err := s.historyDB.GetLastBatchNum()
+	if err != nil && err != sql.ErrNoRows {
+		return err
+	}
+	if err == sql.ErrNoRows {
+		lastBatchNum = 0
+	}
+
+	s.stats.UpdateSync(lastBlockNum, &lastBatchNum)
+
+	log.Infow("Sync init block",
+		"syncLastBlock", s.stats.stats.Sync.LastBlock,
+		"syncBlocksPerc", s.stats.blocksPerc(),
+		"ethFirstBlock", s.stats.stats.Eth.FirstBlock,
+		"ethLastBlock", s.stats.stats.Eth.LastBlock,
+	)
+	log.Infow("Sync init batch",
+		"syncLastBatch", s.stats.stats.Sync.LastBatch,
+		"syncBatchesPerc", s.stats.batchesPerc(s.stats.stats.Sync.LastBatch),
+		"ethLastBatch", s.stats.stats.Eth.LastBatch,
+	)
 	return nil
 }
 
@@ -182,7 +323,14 @@ return nil, nil, err
 	}
 	log.Debugf("ethBlock: num: %v, parent: %v, hash: %v", ethBlock.EthBlockNum, ethBlock.ParentHash.String(), ethBlock.Hash.String())
 
-	log.Debugw("Syncing...", "block", nextBlockNum)
+	if err := s.stats.UpdateEth(s.ethClient); err != nil {
+		return nil, nil, err
+	}
+
+	log.Debugw("Syncing...",
+		"block", nextBlockNum,
+		"ethLastBlock", s.stats.stats.Eth.LastBlock,
+	)
 
 	// Check that the obtianed ethBlock.ParentHash == prevEthBlock.Hash; if not, reorg!
 	if lastSavedBlock != nil {
@@ -247,6 +395,26 @@ // }
 	err = s.historyDB.AddBlockSCData(&blockData)
 	if err != nil {
 		return nil, nil, err
+	}
+
+	batchesLen := len(rollupData.Batches)
+	if batchesLen == 0 {
+		s.stats.UpdateSync(ethBlock.EthBlockNum, nil)
+	} else {
+		s.stats.UpdateSync(ethBlock.EthBlockNum,
+			&rollupData.Batches[batchesLen-1].Batch.BatchNum)
+	}
+	log.Debugw("Synced block",
+		"syncLastBlock", s.stats.stats.Sync.LastBlock,
+		"syncBlocksPerc", s.stats.blocksPerc(),
+		"ethLastBlock", s.stats.stats.Eth.LastBlock,
+	)
+	for _, batchData := range rollupData.Batches {
+		log.Debugw("Synced batch",
+			"syncLastBatch", batchData.Batch.BatchNum,
+			"syncBatchesPerc", s.stats.batchesPerc(int64(batchData.Batch.BatchNum)),
+			"ethLastBatch", s.stats.stats.Eth.LastBatch,
+		)
 	}
 
 	return &blockData, nil, nil
@@ -566,7 +734,7 @@ }
 
 	if varsUpdate {
 		s.vars.Rollup.EthBlockNum = blockNum
-		rollupData.Vars = &s.vars.Rollup
+		rollupData.Vars = s.vars.Rollup.Copy()
 	}
 
 	return &rollupData, nil
@@ -665,7 +833,7 @@ // NOTE: We ignore HEZClaimed
 
 	if varsUpdate {
 		s.vars.Auction.EthBlockNum = blockNum
-		auctionData.Vars = &s.vars.Auction
+		auctionData.Vars = s.vars.Auction.Copy()
 	}
 
 	return &auctionData, nil
@@ -734,7 +902,7 @@ }
 
 	if varsUpdate {
 		s.vars.WDelayer.EthBlockNum = blockNum
-		wDelayerData.Vars = &s.vars.WDelayer
+		wDelayerData.Vars = s.vars.WDelayer.Copy()
 	}
 
 	return &wDelayerData, nil

@@ -10,6 +10,7 @@ "github.com/gin-gonic/gin"
 	"github.com/hermeznetwork/hermez-node/common"
 	"github.com/hermeznetwork/hermez-node/db/statedb"
 	"github.com/hermeznetwork/hermez-node/log"
+	"github.com/hermeznetwork/hermez-node/synchronizer"
 )
 
 func handleNoRoute(c *gin.Context) {
@@ -33,13 +34,15 @@ // DebugAPI is an http API with debugging endpoints
 type DebugAPI struct {
 	addr    string
 	stateDB *statedb.StateDB // synchronizer statedb
+	sync    *synchronizer.Synchronizer
 }
 
 // NewDebugAPI creates a new DebugAPI
-func NewDebugAPI(addr string, stateDB *statedb.StateDB) *DebugAPI {
+func NewDebugAPI(addr string, stateDB *statedb.StateDB, sync *synchronizer.Synchronizer) *DebugAPI {
 	return &DebugAPI{
+		addr:    addr,
 		stateDB: stateDB,
-		addr:    addr,
+		sync:    sync,
 	}
 }
 
@@ -82,6 +85,11 @@ root := a.stateDB.MTGetRoot()
 	c.JSON(http.StatusOK, root)
 }
 
+func (a *DebugAPI) handleSyncStats(c *gin.Context) {
+	stats := a.sync.Stats()
+	c.JSON(http.StatusOK, stats)
+}
+
 // Run starts the http server of the DebugAPI.  To stop it, pass a context with
 // cancelation (see `debugapi_test.go` for an example).
 func (a *DebugAPI) Run(ctx context.Context) error {
@@ -97,6 +105,8 @@ // because the stateDB doesn't store the BatchNum in which an account
 	// is created.
 	debugAPI.GET("sdb/accounts", a.handleAccounts)
 	debugAPI.GET("sdb/accounts/:Idx", a.handleAccount)
+
+	debugAPI.GET("sync/stats", a.handleSyncStats)
 
 	debugAPIServer := &http.Server{
 		Addr:    a.addr,

@@ -50,7 +50,8 @@ err = sdb.MakeCheckpoint() // Make a checkpoint to increment the batchNum
 	require.Nil(t, err)
 
 	addr := "localhost:12345"
-	debugAPI := NewDebugAPI(addr, sdb)
+	// We won't test the sync/stats endpoint, so we can se the Syncrhonizer to nil
+	debugAPI := NewDebugAPI(addr, sdb, nil)
 
 	ctx, cancel := context.WithCancel(context.Background())
 	go func() {

@@ -762,6 +762,16 @@ log.Error("TODO")
 	return nil, errTODO
 }
 
+// RollupLastForgedBatch is the interface to call the smart contract function
+func (c *Client) RollupLastForgedBatch() (int64, error) {
+	c.rw.RLock()
+	defer c.rw.RUnlock()
+
+	currentBlock := c.currentBlock()
+	e := currentBlock.Rollup
+	return int64(len(e.State.ExitRoots)) - 1, nil
+}
+
 // RollupWithdrawCircuit is the interface to call the smart contract function
 func (c *Client) RollupWithdrawCircuit(proofA, proofC [2]*big.Int, proofB [2][2]*big.Int, tokenID uint32, numExitRoot, idx int64, amount *big.Int, instantWithdraw bool) (*types.Transaction, error) {
 	log.Error("TODO")