Add Last db view in kvdb and statedb

Last db view is an opened pebble db which always contains a checkpoint from the
last batch.  Methods to access this last batch are thread safe so that views of
the last checkpoint can be made anywhere and with a consistent view of the
state.

api/account.go

@@ -6,6 +6,8 @@ import (
 	"github.com/gin-gonic/gin"
 	"github.com/hermeznetwork/hermez-node/apitypes"
 	"github.com/hermeznetwork/hermez-node/db/historydb"
+	"github.com/hermeznetwork/hermez-node/db/statedb"
+	"github.com/hermeznetwork/tracerr"
 )
 
 func (a *API) getAccount(c *gin.Context) {
@@ -22,7 +24,7 @@ func (a *API) getAccount(c *gin.Context) {
 	}
 
 	// Get balance from stateDB
-	account, err := a.s.GetAccount(*idx)
+	account, err := a.s.LastGetAccount(*idx)
 	if err != nil {
 		retSQLErr(err, c)
 		return
@@ -56,19 +58,23 @@ func (a *API) getAccounts(c *gin.Context) {
 	}
 
 	// Get balances from stateDB
-	for x, apiAccount := range apiAccounts {
-		idx, err := stringToIdx(string(apiAccount.Idx), "Account Idx")
-		if err != nil {
-			retSQLErr(err, c)
-			return
+	if err := a.s.LastRead(func(sdb *statedb.Last) error {
+		for x, apiAccount := range apiAccounts {
+			idx, err := stringToIdx(string(apiAccount.Idx), "Account Idx")
+			if err != nil {
+				return tracerr.Wrap(err)
+			}
+			account, err := sdb.GetAccount(*idx)
+			if err != nil {
+				return tracerr.Wrap(err)
+			}
+			apiAccounts[x].Balance = apitypes.NewBigIntStr(account.Balance)
+			apiAccounts[x].Nonce = account.Nonce
 		}
-		account, err := a.s.GetAccount(*idx)
-		if err != nil {
-			retSQLErr(err, c)
-			return
-		}
-		apiAccounts[x].Balance = apitypes.NewBigIntStr(account.Balance)
-		apiAccounts[x].Nonce = account.Nonce
+		return nil
+	}); err != nil {
+		retSQLErr(err, c)
+		return
 	}
 
 	// Build succesfull response

api/account_test.go

@@ -10,6 +10,7 @@ import (
 	"github.com/hermeznetwork/hermez-node/db/historydb"
 	"github.com/mitchellh/copystructure"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 type testAccount struct {
@@ -76,40 +77,40 @@ func TestGetAccounts(t *testing.T) {
 	// Filter by BJJ
 	path := fmt.Sprintf("%s?BJJ=%s&limit=%d", endpoint, tc.accounts[0].PublicKey, limit)
 	err := doGoodReqPaginated(path, historydb.OrderAsc, &testAccountsResponse{}, appendIter)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	assert.Greater(t, len(fetchedAccounts), 0)
 	assert.LessOrEqual(t, len(fetchedAccounts), len(tc.accounts))
 	fetchedAccounts = []testAccount{}
 	// Filter by ethAddr
 	path = fmt.Sprintf("%s?hezEthereumAddress=%s&limit=%d", endpoint, tc.accounts[3].EthAddr, limit)
 	err = doGoodReqPaginated(path, historydb.OrderAsc, &testAccountsResponse{}, appendIter)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	assert.Greater(t, len(fetchedAccounts), 0)
 	assert.LessOrEqual(t, len(fetchedAccounts), len(tc.accounts))
 	fetchedAccounts = []testAccount{}
 	// both filters (incompatible)
 	path = fmt.Sprintf("%s?hezEthereumAddress=%s&BJJ=%s&limit=%d", endpoint, tc.accounts[0].EthAddr, tc.accounts[0].PublicKey, limit)
 	err = doBadReq("GET", path, nil, 400)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	fetchedAccounts = []testAccount{}
 	// Filter by token IDs
 	path = fmt.Sprintf("%s?tokenIds=%s&limit=%d", endpoint, stringIds, limit)
 	err = doGoodReqPaginated(path, historydb.OrderAsc, &testAccountsResponse{}, appendIter)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	assert.Greater(t, len(fetchedAccounts), 0)
 	assert.LessOrEqual(t, len(fetchedAccounts), len(tc.accounts))
 	fetchedAccounts = []testAccount{}
 	// Token Ids + bjj
 	path = fmt.Sprintf("%s?tokenIds=%s&BJJ=%s&limit=%d", endpoint, stringIds, tc.accounts[10].PublicKey, limit)
 	err = doGoodReqPaginated(path, historydb.OrderAsc, &testAccountsResponse{}, appendIter)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	assert.Greater(t, len(fetchedAccounts), 0)
 	assert.LessOrEqual(t, len(fetchedAccounts), len(tc.accounts))
 	fetchedAccounts = []testAccount{}
 	// No filters (checks response content)
 	path = fmt.Sprintf("%s?limit=%d", endpoint, limit)
 	err = doGoodReqPaginated(path, historydb.OrderAsc, &testAccountsResponse{}, appendIter)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	assert.Equal(t, len(tc.accounts), len(fetchedAccounts))
 	for i := 0; i < len(fetchedAccounts); i++ {
 		fetchedAccounts[i].Token.ItemID = 0
@@ -132,7 +133,7 @@ func TestGetAccounts(t *testing.T) {
 		}
 	}
 	err = doGoodReqPaginated(path, historydb.OrderDesc, &testAccountsResponse{}, appendIter)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	assert.Equal(t, len(reversedAccounts), len(fetchedAccounts))
 	for i := 0; i < len(fetchedAccounts); i++ {
 		reversedAccounts[i].Token.ItemID = 0
@@ -147,21 +148,21 @@ func TestGetAccounts(t *testing.T) {
 	// 400
 	path = fmt.Sprintf("%s?hezEthereumAddress=hez:0x123456", endpoint)
 	err = doBadReq("GET", path, nil, 400)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
 	// Test GetAccount
 	path = fmt.Sprintf("%s/%s", endpoint, fetchedAccounts[2].Idx)
 	account := testAccount{}
-	assert.NoError(t, doGoodReq("GET", path, nil, &account))
+	require.NoError(t, doGoodReq("GET", path, nil, &account))
 	account.Token.ItemID = 0
 	assert.Equal(t, fetchedAccounts[2], account)
 
 	// 400
 	path = fmt.Sprintf("%s/hez:12345", endpoint)
 	err = doBadReq("GET", path, nil, 400)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// 404
 	path = fmt.Sprintf("%s/hez:10:12345", endpoint)
 	err = doBadReq("GET", path, nil, 404)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 }

api/api_test.go

@@ -355,6 +355,10 @@ func TestMain(m *testing.M) {
 			panic(err)
 		}
 	}
+	// Make a checkpoint to make the accounts available in Last
+	if err := api.s.MakeCheckpoint(); err != nil {
+		panic(err)
+	}
 
 	// Generate Coordinators and add them to HistoryDB
 	const nCoords = 10

api/txspool.go

@@ -170,7 +170,7 @@ func (a *API) verifyPoolL2TxWrite(txw *l2db.PoolL2TxWrite) error {
 		return tracerr.Wrap(err)
 	}
 	// Get public key
-	account, err := a.s.GetAccount(poolTx.FromIdx)
+	account, err := a.s.LastGetAccount(poolTx.FromIdx)
 	if err != nil {
 		return tracerr.Wrap(err)
 	}

coordinator/pipeline_test.go

@@ -150,7 +150,7 @@ func preloadSync(t *testing.T, ethClient *test.Client, sync *synchronizer.Synchr
 	require.Nil(t, err)
 	require.Equal(t, testTokensLen*testUsersLen, len(dbAccounts))
 
-	sdbAccounts, err := stateDB.GetAccounts()
+	sdbAccounts, err := stateDB.TestGetAccounts()
 	require.Nil(t, err)
 	require.Equal(t, testTokensLen*testUsersLen, len(sdbAccounts))
 
@@ -200,12 +200,12 @@ PoolTransfer(0) User2-User3: 300 (126)
 	})
 	require.NoError(t, err)
 	// Sanity check
-	sdbAccounts, err := pipeline.txSelector.LocalAccountsDB().GetAccounts()
+	sdbAccounts, err := pipeline.txSelector.LocalAccountsDB().TestGetAccounts()
 	require.Nil(t, err)
 	require.Equal(t, testTokensLen*testUsersLen, len(sdbAccounts))
 
 	// Sanity check
-	sdbAccounts, err = pipeline.batchBuilder.LocalStateDB().GetAccounts()
+	sdbAccounts, err = pipeline.batchBuilder.LocalStateDB().TestGetAccounts()
 	require.Nil(t, err)
 	require.Equal(t, testTokensLen*testUsersLen, len(sdbAccounts))
 

db/kvdb/kvdb.go

@@ -24,6 +24,9 @@ const (
 	// PathCurrent defines the subpath of the current Batch in the subpath
 	// of the KVDB
 	PathCurrent = "current"
+	// PathLast defines the subpath of the last Batch in the subpath
+	// of the StateDB
+	PathLast = "last"
 )
 
 var (
@@ -42,6 +45,58 @@ type KVDB struct {
 	CurrentBatch common.BatchNum
 	keep         int
 	m            sync.Mutex
+	last         *Last
+}
+
+// Last is a consistent view to the last batch of the stateDB that can
+// be queried concurrently.
+type Last struct {
+	db   *pebble.Storage
+	path string
+	rw   sync.RWMutex
+}
+
+func (k *Last) setNew() error {
+	k.rw.Lock()
+	defer k.rw.Unlock()
+	if k.db != nil {
+		k.db.Close()
+	}
+	lastPath := path.Join(k.path, PathLast)
+	err := os.RemoveAll(lastPath)
+	if err != nil {
+		return tracerr.Wrap(err)
+	}
+	db, err := pebble.NewPebbleStorage(path.Join(k.path, lastPath), false)
+	if err != nil {
+		return tracerr.Wrap(err)
+	}
+	k.db = db
+	return nil
+}
+
+func (k *Last) set(kvdb *KVDB, batchNum common.BatchNum) error {
+	k.rw.Lock()
+	defer k.rw.Unlock()
+	if k.db != nil {
+		k.db.Close()
+	}
+	lastPath := path.Join(k.path, PathLast)
+	if err := kvdb.MakeCheckpointFromTo(batchNum, lastPath); err != nil {
+		return tracerr.Wrap(err)
+	}
+	db, err := pebble.NewPebbleStorage(lastPath, false)
+	if err != nil {
+		return tracerr.Wrap(err)
+	}
+	k.db = db
+	return nil
+}
+
+func (k *Last) close() {
+	k.rw.Lock()
+	defer k.rw.Unlock()
+	k.db.Close()
 }
 
 // NewKVDB creates a new KVDB, allowing to use an in-memory or in-disk storage.
@@ -58,6 +113,9 @@ func NewKVDB(pathDB string, keep int) (*KVDB, error) {
 		path: pathDB,
 		db:   sto,
 		keep: keep,
+		last: &Last{
+			path: pathDB,
+		},
 	}
 	// load currentBatch
 	kvdb.CurrentBatch, err = kvdb.GetCurrentBatch()
@@ -74,6 +132,13 @@ func NewKVDB(pathDB string, keep int) (*KVDB, error) {
 	return kvdb, nil
 }
 
+// LastRead is a thread-safe method to query the last KVDB
+func (kvdb *KVDB) LastRead(fn func(db *pebble.Storage) error) error {
+	kvdb.last.rw.RLock()
+	defer kvdb.last.rw.RUnlock()
+	return fn(kvdb.last.db)
+}
+
 // DB returns the *pebble.Storage from the KVDB
 func (kvdb *KVDB) DB() *pebble.Storage {
 	return kvdb.db
@@ -139,14 +204,21 @@ func (kvdb *KVDB) reset(batchNum common.BatchNum, closeCurrent bool) error {
 		kvdb.db = sto
 		kvdb.CurrentIdx = common.RollupConstReservedIDx // 255
 		kvdb.CurrentBatch = 0
+		if err := kvdb.last.setNew(); err != nil {
+			return tracerr.Wrap(err)
+		}
 
 		return nil
 	}
 
-	// copy 'BatchNumX' to 'current'
+	// copy 'batchNum' to 'current'
 	if err := kvdb.MakeCheckpointFromTo(batchNum, currentPath); err != nil {
 		return tracerr.Wrap(err)
 	}
+	// copy 'batchNum' to 'last'
+	if err := kvdb.last.set(kvdb, batchNum); err != nil {
+		return tracerr.Wrap(err)
+	}
 
 	// open the new 'current'
 	sto, err := pebble.NewPebbleStorage(currentPath, false)
@@ -334,6 +406,10 @@ func (kvdb *KVDB) MakeCheckpoint() error {
 	if err := kvdb.db.Pebble().Checkpoint(checkpointPath); err != nil {
 		return tracerr.Wrap(err)
 	}
+	// copy 'CurrentBatch' to 'last'
+	if err := kvdb.last.set(kvdb, kvdb.CurrentBatch); err != nil {
+		return tracerr.Wrap(err)
+	}
 	// delete old checkpoints
 	if err := kvdb.deleteOldCheckpoints(); err != nil {
 		return tracerr.Wrap(err)
@@ -456,4 +532,5 @@ func pebbleMakeCheckpoint(source, dest string) error {
 // Close the DB
 func (kvdb *KVDB) Close() {
 	kvdb.db.Close()
+	kvdb.last.close()
 }

db/statedb/statedb.go

@@ -11,6 +11,7 @@ import (
 	"github.com/hermeznetwork/tracerr"
 	"github.com/iden3/go-merkletree"
 	"github.com/iden3/go-merkletree/db"
+	"github.com/iden3/go-merkletree/db/pebble"
 )
 
 var (
@@ -58,11 +59,46 @@ type TypeStateDB string
 
 // StateDB represents the StateDB object
 type StateDB struct {
-	path string
-	Typ  TypeStateDB
-	db   *kvdb.KVDB
-	MT   *merkletree.MerkleTree
-	keep int
+	path    string
+	Typ     TypeStateDB
+	db      *kvdb.KVDB
+	nLevels int
+	MT      *merkletree.MerkleTree
+	keep    int
+}
+
+// Last offers a subset of view methods of the StateDB that can be
+// called via the LastRead method of StateDB in a thread-safe manner to obtain
+// a consistent view to the last batch of the StateDB.
+type Last struct {
+	db db.Storage
+}
+
+// GetAccount returns the account for the given Idx
+func (s *Last) GetAccount(idx common.Idx) (*common.Account, error) {
+	return GetAccountInTreeDB(s.db, idx)
+}
+
+// GetCurrentBatch returns the current BatchNum stored in Last.db
+func (s *Last) GetCurrentBatch() (common.BatchNum, error) {
+	cbBytes, err := s.db.Get(kvdb.KeyCurrentBatch)
+	if tracerr.Unwrap(err) == db.ErrNotFound {
+		return 0, nil
+	} else if err != nil {
+		return 0, tracerr.Wrap(err)
+	}
+	return common.BatchNumFromBytes(cbBytes)
+}
+
+// DB returns the underlying storage of Last
+func (s *Last) DB() db.Storage {
+	return s.db
+}
+
+// GetAccounts returns all the accounts in the db.  Use for debugging pruposes
+// only.
+func (s *Last) GetAccounts() ([]common.Account, error) {
+	return getAccounts(s.db)
 }
 
 // NewStateDB creates a new StateDB, allowing to use an in-memory or in-disk
@@ -89,14 +125,72 @@ func NewStateDB(pathDB string, keep int, typ TypeStateDB, nLevels int) (*StateDB
 	}
 
 	return &StateDB{
-		path: pathDB,
-		db:   kv,
-		MT:   mt,
-		Typ:  typ,
-		keep: keep,
+		path:    pathDB,
+		db:      kv,
+		nLevels: nLevels,
+		MT:      mt,
+		Typ:     typ,
+		keep:    keep,
 	}, nil
 }
 
+// LastRead is a thread-safe method to query the last checkpoint of the StateDB
+// via the Last type methods
+func (s *StateDB) LastRead(fn func(sdbLast *Last) error) error {
+	return s.db.LastRead(
+		func(db *pebble.Storage) error {
+			return fn(&Last{
+				db: db,
+			})
+		},
+	)
+}
+
+// LastGetAccount is a thread-safe method to query an account in the last
+// checkpoint of the StateDB.
+func (s *StateDB) LastGetAccount(idx common.Idx) (*common.Account, error) {
+	var account *common.Account
+	if err := s.LastRead(func(sdb *Last) error {
+		var err error
+		account, err = sdb.GetAccount(idx)
+		return err
+	}); err != nil {
+		return nil, tracerr.Wrap(err)
+	}
+	return account, nil
+}
+
+// LastGetCurrentBatch is a thread-safe method to get the current BatchNum in
+// the last checkpoint of the StateDB.
+func (s *StateDB) LastGetCurrentBatch() (common.BatchNum, error) {
+	var batchNum common.BatchNum
+	if err := s.LastRead(func(sdb *Last) error {
+		var err error
+		batchNum, err = sdb.GetCurrentBatch()
+		return err
+	}); err != nil {
+		return 0, tracerr.Wrap(err)
+	}
+	return batchNum, nil
+}
+
+// LastMTGetRoot returns the root of the underlying Merkle Tree in the last
+// checkpoint of the StateDB.
+func (s *StateDB) LastMTGetRoot() (*big.Int, error) {
+	var root *big.Int
+	if err := s.LastRead(func(sdb *Last) error {
+		mt, err := merkletree.NewMerkleTree(sdb.DB().WithPrefix(PrefixKeyMT), s.nLevels)
+		if err != nil {
+			return tracerr.Wrap(err)
+		}
+		root = mt.Root().BigInt()
+		return nil
+	}); err != nil {
+		return nil, tracerr.Wrap(err)
+	}
+	return root, nil
+}
+
 // MakeCheckpoint does a checkpoint at the given batchNum in the defined path.
 // Internally this advances & stores the current BatchNum, and then stores a
 // Checkpoint of the current state of the StateDB.
@@ -115,8 +209,8 @@ func (s *StateDB) CurrentIdx() common.Idx {
 	return s.db.CurrentIdx
 }
 
-// GetCurrentBatch returns the current BatchNum stored in the StateDB.db
-func (s *StateDB) GetCurrentBatch() (common.BatchNum, error) {
+// getCurrentBatch returns the current BatchNum stored in the StateDB.db
+func (s *StateDB) getCurrentBatch() (common.BatchNum, error) {
 	return s.db.GetCurrentBatch()
 }
 
@@ -157,35 +251,50 @@ func (s *StateDB) GetAccount(idx common.Idx) (*common.Account, error) {
 	return GetAccountInTreeDB(s.db.DB(), idx)
 }
 
-// GetAccounts returns all the accounts in the db.  Use for debugging pruposes
-// only.
-func (s *StateDB) GetAccounts() ([]common.Account, error) {
-	idxDB := s.db.StorageWithPrefix(PrefixKeyIdx)
-	idxs := []common.Idx{}
-	// NOTE: Current implementation of Iterate in the pebble interface is
-	// not efficient, as it iterates over all keys.  Improve it following
-	// this example: https://github.com/cockroachdb/pebble/pull/923/files
+func accountsIter(db db.Storage, fn func(a *common.Account) (bool, error)) error {
+	idxDB := db.WithPrefix(PrefixKeyIdx)
 	if err := idxDB.Iterate(func(k []byte, v []byte) (bool, error) {
 		idx, err := common.IdxFromBytes(k)
 		if err != nil {
 			return false, tracerr.Wrap(err)
 		}
-		idxs = append(idxs, idx)
-		return true, nil
+		acc, err := GetAccountInTreeDB(db, idx)
+		if err != nil {
+			return false, tracerr.Wrap(err)
+		}
+		ok, err := fn(acc)
+		if err != nil {
+			return false, tracerr.Wrap(err)
+		}
+		return ok, nil
 	}); err != nil {
-		return nil, tracerr.Wrap(err)
+		return tracerr.Wrap(err)
 	}
+	return nil
+}
+
+func getAccounts(db db.Storage) ([]common.Account, error) {
 	accs := []common.Account{}
-	for i := range idxs {
-		acc, err := s.GetAccount(idxs[i])
-		if err != nil {
-			return nil, tracerr.Wrap(err)
-		}
-		accs = append(accs, *acc)
+	if err := accountsIter(
+		db,
+		func(a *common.Account) (bool, error) {
+			accs = append(accs, *a)
+			return true, nil
+		},
+	); err != nil {
+		return nil, tracerr.Wrap(err)
 	}
 	return accs, nil
 }
 
+// TestGetAccounts returns all the accounts in the db.  Use only in tests.
+// Outside tests getting all the accounts is discouraged because it's an
+// expensive operation, but if you must do it, use `LastRead()` method to get a
+// thread-safe and consistent view of the stateDB.
+func (s *StateDB) TestGetAccounts() ([]common.Account, error) {
+	return getAccounts(s.db.DB())
+}
+
 // GetAccountInTreeDB is abstracted from StateDB to be used from StateDB and
 // from ExitTree.  GetAccount returns the account for the given Idx
 func GetAccountInTreeDB(sto db.Storage, idx common.Idx) (*common.Account, error) {
@@ -336,11 +445,6 @@ func (s *StateDB) MTGetProof(idx common.Idx) (*merkletree.CircomVerifierProof, e
 	return p, nil
 }
 
-// MTGetRoot returns the current root of the underlying Merkle Tree
-func (s *StateDB) MTGetRoot() *big.Int {
-	return s.MT.Root().BigInt()
-}
-
 // Close the StateDB
 func (s *StateDB) Close() {
 	s.db.Close()

db/statedb/statedb_test.go

@@ -43,10 +43,10 @@ func newAccount(t *testing.T, i int) *common.Account {
 func TestNewStateDBIntermediateState(t *testing.T) {
 	dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
-	defer assert.NoError(t, os.RemoveAll(dir))
+	defer require.NoError(t, os.RemoveAll(dir))
 
 	sdb, err := NewStateDB(dir, 128, TypeTxSelector, 0)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
 	// test values
 	k0 := []byte("testkey0")
@@ -56,19 +56,26 @@ func TestNewStateDBIntermediateState(t *testing.T) {
 
 	// store some data
 	tx, err := sdb.db.DB().NewTx()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	err = tx.Put(k0, v0)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	err = tx.Commit()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	v, err := sdb.db.DB().Get(k0)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	assert.Equal(t, v0, v)
 
-	// Close PebbleDB before creating a new StateDB
-	err = sdb.db.DB().Pebble().Close()
+	// k0 not yet in last
+	err = sdb.LastRead(func(sdb *Last) error {
+		_, err := sdb.DB().Get(k0)
+		assert.Equal(t, db.ErrNotFound, tracerr.Unwrap(err))
+		return nil
+	})
 	require.NoError(t, err)
 
+	// Close PebbleDB before creating a new StateDB
+	sdb.Close()
+
 	// call NewStateDB which should get the db at the last checkpoint state
 	// executing a Reset (discarding the last 'testkey0'&'testvalue0' data)
 	sdb, err = NewStateDB(dir, 128, TypeTxSelector, 0)
@@ -78,54 +85,90 @@ func TestNewStateDBIntermediateState(t *testing.T) {
 	assert.Equal(t, db.ErrNotFound, tracerr.Unwrap(err))
 	assert.Nil(t, v)
 
+	// k0 not in last
+	err = sdb.LastRead(func(sdb *Last) error {
+		_, err := sdb.DB().Get(k0)
+		assert.Equal(t, db.ErrNotFound, tracerr.Unwrap(err))
+		return nil
+	})
+	require.NoError(t, err)
+
 	// store the same data from the beginning that has ben lost since last NewStateDB
 	tx, err = sdb.db.DB().NewTx()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	err = tx.Put(k0, v0)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	err = tx.Commit()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	v, err = sdb.db.DB().Get(k0)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	assert.Equal(t, v0, v)
 
+	// k0 yet not in last
+	err = sdb.LastRead(func(sdb *Last) error {
+		_, err := sdb.DB().Get(k0)
+		assert.Equal(t, db.ErrNotFound, tracerr.Unwrap(err))
+		return nil
+	})
+	require.NoError(t, err)
+
 	// make checkpoints with the current state
-	bn, err := sdb.db.GetCurrentBatch()
-	assert.NoError(t, err)
+	bn, err := sdb.getCurrentBatch()
+	require.NoError(t, err)
 	assert.Equal(t, common.BatchNum(0), bn)
 	err = sdb.db.MakeCheckpoint()
-	assert.NoError(t, err)
-	bn, err = sdb.db.GetCurrentBatch()
-	assert.NoError(t, err)
+	require.NoError(t, err)
+	bn, err = sdb.getCurrentBatch()
+	require.NoError(t, err)
 	assert.Equal(t, common.BatchNum(1), bn)
 
+	// k0 in last
+	err = sdb.LastRead(func(sdb *Last) error {
+		v, err := sdb.DB().Get(k0)
+		require.NoError(t, err)
+		assert.Equal(t, v0, v)
+		return nil
+	})
+	require.NoError(t, err)
+
 	// write more data
 	tx, err = sdb.db.DB().NewTx()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	err = tx.Put(k1, v1)
-	assert.NoError(t, err)
+	require.NoError(t, err)
+	err = tx.Put(k0, v1) // overwrite k0 with v1
+	require.NoError(t, err)
 	err = tx.Commit()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
 	v, err = sdb.db.DB().Get(k1)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	assert.Equal(t, v1, v)
 
-	// Close PebbleDB before creating a new StateDB
-	err = sdb.db.DB().Pebble().Close()
+	err = sdb.LastRead(func(sdb *Last) error {
+		v, err := sdb.DB().Get(k0)
+		require.NoError(t, err)
+		assert.Equal(t, v0, v)
+		return nil
+	})
 	require.NoError(t, err)
 
+	// Close PebbleDB before creating a new StateDB
+	sdb.Close()
+
 	// call NewStateDB which should get the db at the last checkpoint state
 	// executing a Reset (discarding the last 'testkey1'&'testvalue1' data)
 	sdb, err = NewStateDB(dir, 128, TypeTxSelector, 0)
 	require.NoError(t, err)
 
-	bn, err = sdb.db.GetCurrentBatch()
-	assert.NoError(t, err)
+	bn, err = sdb.getCurrentBatch()
+	require.NoError(t, err)
 	assert.Equal(t, common.BatchNum(1), bn)
 
+	// we closed the db without doing a checkpoint after overwriting k0, so
+	// it's back to v0
 	v, err = sdb.db.DB().Get(k0)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	assert.Equal(t, v0, v)
 
 	v, err = sdb.db.DB().Get(k1)
@@ -137,10 +180,10 @@ func TestNewStateDBIntermediateState(t *testing.T) {
 func TestStateDBWithoutMT(t *testing.T) {
 	dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
-	defer assert.NoError(t, os.RemoveAll(dir))
+	defer require.NoError(t, os.RemoveAll(dir))
 
 	sdb, err := NewStateDB(dir, 128, TypeTxSelector, 0)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
 	// create test accounts
 	var accounts []*common.Account
@@ -157,20 +200,20 @@ func TestStateDBWithoutMT(t *testing.T) {
 	// add test accounts
 	for i := 0; i < len(accounts); i++ {
 		_, err = sdb.CreateAccount(accounts[i].Idx, accounts[i])
-		assert.NoError(t, err)
+		require.NoError(t, err)
 	}
 
 	for i := 0; i < len(accounts); i++ {
 		existingAccount := accounts[i].Idx
 		accGetted, err := sdb.GetAccount(existingAccount)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		assert.Equal(t, accounts[i], accGetted)
 	}
 
 	// try already existing idx and get error
 	existingAccount := common.Idx(256)
 	_, err = sdb.GetAccount(existingAccount) // check that exist
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	_, err = sdb.CreateAccount(common.Idx(256), accounts[1]) // check that can not be created twice
 	assert.NotNil(t, err)
 	assert.Equal(t, ErrAccountAlreadyExists, tracerr.Unwrap(err))
@@ -180,7 +223,7 @@ func TestStateDBWithoutMT(t *testing.T) {
 		accounts[i].Nonce = accounts[i].Nonce + 1
 		existingAccount = common.Idx(i)
 		_, err = sdb.UpdateAccount(existingAccount, accounts[i])
-		assert.NoError(t, err)
+		require.NoError(t, err)
 	}
 
 	_, err = sdb.MTGetProof(common.Idx(1))
@@ -191,10 +234,10 @@ func TestStateDBWithoutMT(t *testing.T) {
 func TestStateDBWithMT(t *testing.T) {
 	dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
-	defer assert.NoError(t, os.RemoveAll(dir))
+	defer require.NoError(t, os.RemoveAll(dir))
 
 	sdb, err := NewStateDB(dir, 128, TypeSynchronizer, 32)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
 	// create test accounts
 	var accounts []*common.Account
@@ -210,33 +253,33 @@ func TestStateDBWithMT(t *testing.T) {
 	// add test accounts
 	for i := 0; i < len(accounts); i++ {
 		_, err = sdb.CreateAccount(accounts[i].Idx, accounts[i])
-		assert.NoError(t, err)
+		require.NoError(t, err)
 	}
 
 	for i := 0; i < len(accounts); i++ {
 		accGetted, err := sdb.GetAccount(accounts[i].Idx)
-		assert.NoError(t, err)
+		require.NoError(t, err)
 		assert.Equal(t, accounts[i], accGetted)
 	}
 
 	// try already existing idx and get error
 	_, err = sdb.GetAccount(common.Idx(256)) // check that exist
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	_, err = sdb.CreateAccount(common.Idx(256), accounts[1]) // check that can not be created twice
 	assert.NotNil(t, err)
 	assert.Equal(t, ErrAccountAlreadyExists, tracerr.Unwrap(err))
 
 	_, err = sdb.MTGetProof(common.Idx(256))
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
 	// update accounts
 	for i := 0; i < len(accounts); i++ {
 		accounts[i].Nonce = accounts[i].Nonce + 1
 		_, err = sdb.UpdateAccount(accounts[i].Idx, accounts[i])
-		assert.NoError(t, err)
+		require.NoError(t, err)
 	}
 	a, err := sdb.GetAccount(common.Idx(256)) // check that account value has been updated
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	assert.Equal(t, accounts[0].Nonce, a.Nonce)
 }
 
@@ -245,10 +288,13 @@ func TestStateDBWithMT(t *testing.T) {
 func TestCheckpoints(t *testing.T) {
 	dir, err := ioutil.TempDir("", "sdb")
 	require.NoError(t, err)
-	defer assert.NoError(t, os.RemoveAll(dir))
+	defer require.NoError(t, os.RemoveAll(dir))
 
 	sdb, err := NewStateDB(dir, 128, TypeSynchronizer, 32)
-	assert.NoError(t, err)
+	require.NoError(t, err)
+
+	err = sdb.Reset(0)
+	require.NoError(t, err)
 
 	// create test accounts
 	var accounts []*common.Account
@@ -259,22 +305,33 @@ func TestCheckpoints(t *testing.T) {
 	// add test accounts
 	for i := 0; i < len(accounts); i++ {
 		_, err = sdb.CreateAccount(accounts[i].Idx, accounts[i])
-		assert.NoError(t, err)
+		require.NoError(t, err)
 	}
+	// account doesn't exist in Last checkpoint
+	_, err = sdb.LastGetAccount(accounts[0].Idx)
+	assert.Equal(t, db.ErrNotFound, tracerr.Unwrap(err))
 
 	// do checkpoints and check that currentBatch is correct
-	err = sdb.db.MakeCheckpoint()
-	assert.NoError(t, err)
-	cb, err := sdb.db.GetCurrentBatch()
-	assert.NoError(t, err)
+	err = sdb.MakeCheckpoint()
+	require.NoError(t, err)
+	cb, err := sdb.getCurrentBatch()
+	require.NoError(t, err)
 	assert.Equal(t, common.BatchNum(1), cb)
 
+	// account exists in Last checkpoint
+	accCur, err := sdb.GetAccount(accounts[0].Idx)
+	require.NoError(t, err)
+	accLast, err := sdb.LastGetAccount(accounts[0].Idx)
+	require.NoError(t, err)
+	assert.Equal(t, accounts[0], accLast)
+	assert.Equal(t, accCur, accLast)
+
 	for i := 1; i < 10; i++ {
-		err = sdb.db.MakeCheckpoint()
-		assert.NoError(t, err)
+		err = sdb.MakeCheckpoint()
+		require.NoError(t, err)
 
-		cb, err = sdb.db.GetCurrentBatch()
-		assert.NoError(t, err)
+		cb, err = sdb.getCurrentBatch()
+		require.NoError(t, err)
 		assert.Equal(t, common.BatchNum(i+1), cb)
 	}
 
@@ -282,7 +339,7 @@ func TestCheckpoints(t *testing.T) {
 
 	// reset checkpoint
 	err = sdb.Reset(3)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
 	// check that reset can be repeated (as there exist the 'current' and
 	// 'BatchNum3', from where the 'current' is a copy)
@@ -290,21 +347,21 @@ func TestCheckpoints(t *testing.T) {
 	require.NoError(t, err)
 
 	// check that currentBatch is as expected after Reset
-	cb, err = sdb.db.GetCurrentBatch()
-	assert.NoError(t, err)
+	cb, err = sdb.getCurrentBatch()
+	require.NoError(t, err)
 	assert.Equal(t, common.BatchNum(3), cb)
 
 	// advance one checkpoint and check that currentBatch is fine
-	err = sdb.db.MakeCheckpoint()
-	assert.NoError(t, err)
-	cb, err = sdb.db.GetCurrentBatch()
-	assert.NoError(t, err)
+	err = sdb.MakeCheckpoint()
+	require.NoError(t, err)
+	cb, err = sdb.getCurrentBatch()
+	require.NoError(t, err)
 	assert.Equal(t, common.BatchNum(4), cb)
 
 	err = sdb.db.DeleteCheckpoint(common.BatchNum(1))
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	err = sdb.db.DeleteCheckpoint(common.BatchNum(2))
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	err = sdb.db.DeleteCheckpoint(common.BatchNum(1)) // does not exist, should return err
 	assert.NotNil(t, err)
 	err = sdb.db.DeleteCheckpoint(common.BatchNum(2)) // does not exist, should return err
@@ -313,43 +370,43 @@ func TestCheckpoints(t *testing.T) {
 	// Create a LocalStateDB from the initial StateDB
 	dirLocal, err := ioutil.TempDir("", "ldb")
 	require.NoError(t, err)
-	defer assert.NoError(t, os.RemoveAll(dirLocal))
+	defer require.NoError(t, os.RemoveAll(dirLocal))
 	ldb, err := NewLocalStateDB(dirLocal, 128, sdb, TypeBatchBuilder, 32)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
 	// get checkpoint 4 from sdb (StateDB) to ldb (LocalStateDB)
 	err = ldb.Reset(4, true)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// check that currentBatch is 4 after the Reset
-	cb, err = ldb.db.GetCurrentBatch()
-	assert.NoError(t, err)
+	cb, err = ldb.getCurrentBatch()
+	require.NoError(t, err)
 	assert.Equal(t, common.BatchNum(4), cb)
 	// advance one checkpoint in ldb
-	err = ldb.db.MakeCheckpoint()
-	assert.NoError(t, err)
-	cb, err = ldb.db.GetCurrentBatch()
-	assert.NoError(t, err)
+	err = ldb.MakeCheckpoint()
+	require.NoError(t, err)
+	cb, err = ldb.getCurrentBatch()
+	require.NoError(t, err)
 	assert.Equal(t, common.BatchNum(5), cb)
 
 	// Create a 2nd LocalStateDB from the initial StateDB
 	dirLocal2, err := ioutil.TempDir("", "ldb2")
 	require.NoError(t, err)
-	defer assert.NoError(t, os.RemoveAll(dirLocal2))
+	defer require.NoError(t, os.RemoveAll(dirLocal2))
 	ldb2, err := NewLocalStateDB(dirLocal2, 128, sdb, TypeBatchBuilder, 32)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
 	// get checkpoint 4 from sdb (StateDB) to ldb (LocalStateDB)
 	err = ldb2.Reset(4, true)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	// check that currentBatch is 4 after the Reset
 	cb, err = ldb2.db.GetCurrentBatch()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	assert.Equal(t, common.BatchNum(4), cb)
 	// advance one checkpoint in ldb2
 	err = ldb2.db.MakeCheckpoint()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	cb, err = ldb2.db.GetCurrentBatch()
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	assert.Equal(t, common.BatchNum(5), cb)
 
 	debug := false
@@ -365,7 +422,7 @@ func TestStateDBGetAccounts(t *testing.T) {
 	require.NoError(t, err)
 
 	sdb, err := NewStateDB(dir, 128, TypeTxSelector, 0)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
 	// create test accounts
 	var accounts []common.Account
@@ -380,14 +437,14 @@ func TestStateDBGetAccounts(t *testing.T) {
 		require.NoError(t, err)
 	}
 
-	dbAccounts, err := sdb.GetAccounts()
+	dbAccounts, err := sdb.TestGetAccounts()
 	require.NoError(t, err)
 	assert.Equal(t, accounts, dbAccounts)
 }
 
 func printCheckpoints(t *testing.T, path string) {
 	files, err := ioutil.ReadDir(path)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
 	fmt.Println(path)
 	for _, f := range files {
@@ -409,7 +466,7 @@ func bigFromStr(h string, u int) *big.Int {
 func TestCheckAccountsTreeTestVectors(t *testing.T) {
 	dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
-	defer assert.NoError(t, os.RemoveAll(dir))
+	defer require.NoError(t, os.RemoveAll(dir))
 
 	sdb, err := NewStateDB(dir, 128, TypeSynchronizer, 32)
 	require.NoError(t, err)
@@ -483,7 +540,7 @@ func TestCheckAccountsTreeTestVectors(t *testing.T) {
 func TestListCheckpoints(t *testing.T) {
 	dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
-	defer assert.NoError(t, os.RemoveAll(dir))
+	defer require.NoError(t, os.RemoveAll(dir))
 
 	sdb, err := NewStateDB(dir, 128, TypeSynchronizer, 32)
 	require.NoError(t, err)
@@ -491,7 +548,7 @@ func TestListCheckpoints(t *testing.T) {
 	numCheckpoints := 16
 	// do checkpoints
 	for i := 0; i < numCheckpoints; i++ {
-		err = sdb.db.MakeCheckpoint()
+		err = sdb.MakeCheckpoint()
 		require.NoError(t, err)
 	}
 	list, err := sdb.db.ListCheckpoints()
@@ -515,7 +572,7 @@ func TestListCheckpoints(t *testing.T) {
 func TestDeleteOldCheckpoints(t *testing.T) {
 	dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
-	defer assert.NoError(t, os.RemoveAll(dir))
+	defer require.NoError(t, os.RemoveAll(dir))
 
 	keep := 16
 	sdb, err := NewStateDB(dir, keep, TypeSynchronizer, 32)
@@ -525,7 +582,7 @@ func TestDeleteOldCheckpoints(t *testing.T) {
 	// do checkpoints and check that we never have more than `keep`
 	// checkpoints
 	for i := 0; i < numCheckpoints; i++ {
-		err = sdb.db.MakeCheckpoint()
+		err = sdb.MakeCheckpoint()
 		require.NoError(t, err)
 		checkpoints, err := sdb.db.ListCheckpoints()
 		require.NoError(t, err)

synchronizer/synchronizer_test.go

@@ -17,6 +17,7 @@ import (
 	"github.com/hermeznetwork/hermez-node/db/historydb"
 	"github.com/hermeznetwork/hermez-node/db/statedb"
 	"github.com/hermeznetwork/hermez-node/eth"
+	"github.com/hermeznetwork/hermez-node/log"
 	"github.com/hermeznetwork/hermez-node/test"
 	"github.com/hermeznetwork/hermez-node/test/til"
 	"github.com/jinzhu/copier"
@@ -253,7 +254,7 @@ func checkSyncBlock(t *testing.T, s *Synchronizer, blockNum int, block, syncBloc
 	// Compare accounts from HistoryDB with StateDB (they should match)
 	dbAccounts, err := s.historyDB.GetAllAccounts()
 	require.NoError(t, err)
-	sdbAccounts, err := s.stateDB.GetAccounts()
+	sdbAccounts, err := s.stateDB.TestGetAccounts()
 	require.NoError(t, err)
 	assertEqualAccountsHistoryDBStateDB(t, dbAccounts, sdbAccounts)
 }
@@ -338,6 +339,7 @@ func TestSyncGeneral(t *testing.T) {
 	s, err := NewSynchronizer(client, historyDB, stateDB, Config{
 		StatsRefreshPeriod: 0 * time.Second,
 	})
+	log.Error(err)
 	require.NoError(t, err)
 
 	ctx := context.Background()
@@ -651,7 +653,7 @@ func TestSyncGeneral(t *testing.T) {
 	// Accounts in HistoryDB and StateDB must be empty
 	dbAccounts, err := s.historyDB.GetAllAccounts()
 	require.NoError(t, err)
-	sdbAccounts, err := s.stateDB.GetAccounts()
+	sdbAccounts, err := s.stateDB.TestGetAccounts()
 	require.NoError(t, err)
 	assert.Equal(t, 0, len(dbAccounts))
 	assertEqualAccountsHistoryDBStateDB(t, dbAccounts, sdbAccounts)
@@ -690,7 +692,7 @@ func TestSyncGeneral(t *testing.T) {
 	// Accounts in HistoryDB and StateDB is only 2 entries
 	dbAccounts, err = s.historyDB.GetAllAccounts()
 	require.NoError(t, err)
-	sdbAccounts, err = s.stateDB.GetAccounts()
+	sdbAccounts, err = s.stateDB.TestGetAccounts()
 	require.NoError(t, err)
 	assert.Equal(t, 2, len(dbAccounts))
 	assertEqualAccountsHistoryDBStateDB(t, dbAccounts, sdbAccounts)

test/debugapi/debugapi.go

@@ -55,7 +55,7 @@ func (a *DebugAPI) handleAccount(c *gin.Context) {
 		badReq(err, c)
 		return
 	}
-	account, err := a.stateDB.GetAccount(common.Idx(uri.Idx))
+	account, err := a.stateDB.LastGetAccount(common.Idx(uri.Idx))
 	if err != nil {
 		badReq(err, c)
 		return
@@ -64,8 +64,12 @@ func (a *DebugAPI) handleAccount(c *gin.Context) {
 }
 
 func (a *DebugAPI) handleAccounts(c *gin.Context) {
-	accounts, err := a.stateDB.GetAccounts()
-	if err != nil {
+	var accounts []common.Account
+	if err := a.stateDB.LastRead(func(sdb *statedb.Last) error {
+		var err error
+		accounts, err = sdb.GetAccounts()
+		return err
+	}); err != nil {
 		badReq(err, c)
 		return
 	}
@@ -73,7 +77,7 @@ func (a *DebugAPI) handleAccounts(c *gin.Context) {
 }
 
 func (a *DebugAPI) handleCurrentBatch(c *gin.Context) {
-	batchNum, err := a.stateDB.GetCurrentBatch()
+	batchNum, err := a.stateDB.LastGetCurrentBatch()
 	if err != nil {
 		badReq(err, c)
 		return
@@ -82,7 +86,11 @@ func (a *DebugAPI) handleCurrentBatch(c *gin.Context) {
 }
 
 func (a *DebugAPI) handleMTRoot(c *gin.Context) {
-	root := a.stateDB.MTGetRoot()
+	root, err := a.stateDB.LastMTGetRoot()
+	if err != nil {
+		badReq(err, c)
+		return
+	}
 	c.JSON(http.StatusOK, root)
 }
 

test/debugapi/debugapi_test.go

@@ -66,6 +66,9 @@ func TestDebugAPI(t *testing.T) {
 		_, err = sdb.CreateAccount(account.Idx, account)
 		require.Nil(t, err)
 	}
+	// Make a checkpoint (batchNum 2) to make the accounts available in Last
+	err = sdb.MakeCheckpoint()
+	require.Nil(t, err)
 
 	url := fmt.Sprintf("http://%v/debug/", addr)
 
@@ -73,7 +76,7 @@ func TestDebugAPI(t *testing.T) {
 	req, err := sling.New().Get(url).Path("sdb/batchnum").ReceiveSuccess(&batchNum)
 	require.Equal(t, http.StatusOK, req.StatusCode)
 	require.Nil(t, err)
-	assert.Equal(t, common.BatchNum(1), batchNum)
+	assert.Equal(t, common.BatchNum(2), batchNum)
 
 	var mtroot *big.Int
 	req, err = sling.New().Get(url).Path("sdb/mtroot").ReceiveSuccess(&mtroot)

txprocessor/zkinputsgen_test.go

@@ -176,7 +176,7 @@ func TestZKInputsEmpty(t *testing.T) {
 	assert.Equal(t, "0", ptOut.ZKInputs.Metadata.NewExitRootRaw.BigInt().String())
 
 	// check that there are no accounts
-	accs, err := sdb.GetAccounts()
+	accs, err := sdb.TestGetAccounts()
 	require.NoError(t, err)
 	assert.Equal(t, 0, len(accs))
 
@@ -208,7 +208,7 @@ func TestZKInputsEmpty(t *testing.T) {
 	rootNonZero := sdb.MT.Root()
 
 	// check that there is 1 account
-	accs, err = sdb.GetAccounts()
+	accs, err = sdb.TestGetAccounts()
 	require.NoError(t, err)
 	assert.Equal(t, 1, len(accs))
 
@@ -234,7 +234,7 @@ func TestZKInputsEmpty(t *testing.T) {
 	assert.Equal(t, "0", ptOut.ZKInputs.Metadata.NewExitRootRaw.BigInt().String())
 
 	// check that there is still 1 account
-	accs, err = sdb.GetAccounts()
+	accs, err = sdb.TestGetAccounts()
 	require.NoError(t, err)
 	assert.Equal(t, 1, len(accs))