db: cache compaction chain tip in db (#369)

* Replace JSON with RLP in levelDB implementation.
* Make sure blocks to sync following compaction chain tip

10 files changed, 281 insertions, 75 deletions

diff --git a/core/consensus.go b/core/consensus.go
index a6d8037..a0336ed 100644
--- a/core/consensus.go
+++ b/core/consensus.go
@@ -1003,6 +1003,14 @@ func (con *Consensus) preProcessBlock(b *types.Block) (err error) {
 
 // deliverBlock deliver a block to application layer.
 func (con *Consensus) deliverBlock(b *types.Block) {
+	if err := con.db.UpdateBlock(*b); err != nil {
+		panic(err)
+	}
+	if err := con.db.PutCompactionChainTipInfo(
+		b.Hash, b.Finalization.Height); err != nil {
+		panic(err)
+	}
+	con.cfgModule.untouchTSigHash(b.Hash)
 	con.logger.Debug("Calling Application.BlockDelivered", "block", b)
 	con.app.BlockDelivered(b.Hash, b.Position, b.Finalization.Clone())
 	if b.Position.Round == con.roundToNotify {
@@ -1032,6 +1040,9 @@ func (con *Consensus) deliverBlock(b *types.Block) {
 			con.roundToNotify, b.Finalization.Height)
 		con.roundToNotify++
 	}
+	if con.debugApp != nil {
+		con.debugApp.BlockReady(b.Hash)
+	}
 }
 
 // processBlock is the entry point to submit one block to a Consensus instance.
@@ -1072,14 +1083,7 @@ func (con *Consensus) processBlock(block *types.Block) (err error) {
 		"delivered", con.ccModule.lastDeliveredBlock(),
 		"pending", con.ccModule.lastPendingBlock())
 	for _, b := range deliveredBlocks {
-		if err = con.db.UpdateBlock(*b); err != nil {
-			panic(err)
-		}
-		con.cfgModule.untouchTSigHash(b.Hash)
 		con.deliverBlock(b)
-		if con.debugApp != nil {
-			con.debugApp.BlockReady(b.Hash)
-		}
 	}
 	if err = con.lattice.PurgeBlocks(deliveredBlocks); err != nil {
 		return
diff --git a/core/consensus_test.go b/core/consensus_test.go
index 16efae0..84df645 100644
--- a/core/consensus_test.go
+++ b/core/consensus_test.go
@@ -451,6 +451,7 @@ func (s *ConsensusTestSuite) TestSimpleDeliverBlock() {
 			nb.wait()
 		}
 		verify(obj.app)
+		req.NoError(test.VerifyDB(obj.con.db))
 	}
 }
 
diff --git a/core/db/interfaces.go b/core/db/interfaces.go
index 5e13dc6..3ffba4a 100644
--- a/core/db/interfaces.go
+++ b/core/db/interfaces.go
@@ -38,6 +38,11 @@ var (
 	ErrClosed = fmt.Errorf("db closed")
 	// ErrNotImplemented is the error that some interface is not implemented.
 	ErrNotImplemented = fmt.Errorf("not implemented")
+	// ErrInvalidCompactionChainTipHeight means the newly updated height of
+	// the tip of compaction chain is invalid, usually means it's smaller than
+	// current cached one.
+	ErrInvalidCompactionChainTipHeight = fmt.Errorf(
+		"invalid compaction chain tip height")
 )
 
 // Database is the interface for a Database.
@@ -55,12 +60,18 @@ type Reader interface {
 	HasBlock(hash common.Hash) bool
 	GetBlock(hash common.Hash) (types.Block, error)
 	GetAllBlocks() (BlockIterator, error)
+
+	// GetCompactionChainTipInfo returns the block hash and finalization height
+	// of the tip block of compaction chain. Empty hash and zero height means
+	// the compaction chain is empty.
+	GetCompactionChainTipInfo() (common.Hash, uint64)
 }
 
 // Writer defines the interface for writing blocks into DB.
 type Writer interface {
 	UpdateBlock(block types.Block) error
 	PutBlock(block types.Block) error
+	PutCompactionChainTipInfo(common.Hash, uint64) error
 }
 
 // BlockIterator defines an iterator on blocks hold
diff --git a/core/db/level-db.go b/core/db/level-db.go
index 6983d3a..238c38e 100644
--- a/core/db/level-db.go
+++ b/core/db/level-db.go
@@ -18,14 +18,23 @@
 package db
 
 import (
-	"encoding/json"
-
 	"github.com/syndtr/goleveldb/leveldb"
 
 	"github.com/dexon-foundation/dexon-consensus/common"
 	"github.com/dexon-foundation/dexon-consensus/core/types"
+	"github.com/dexon-foundation/dexon/rlp"
+)
+
+var (
+	blockKeyPrefix            = []byte("b-")
+	compactionChainTipInfoKey = []byte("cc-tip")
 )
 
+type compactionChainTipInfo struct {
+	Height uint64      `json:"height"`
+	Hash   common.Hash `json:"hash"`
+}
+
 // LevelDBBackedDB is a leveldb backed DB implementation.
 type LevelDBBackedDB struct {
 	db *leveldb.DB
@@ -50,7 +59,7 @@ func (lvl *LevelDBBackedDB) Close() error {
 
 // HasBlock implements the Reader.Has method.
 func (lvl *LevelDBBackedDB) HasBlock(hash common.Hash) bool {
-	exists, err := lvl.db.Has([]byte(hash[:]), nil)
+	exists, err := lvl.internalHasBlock(lvl.getBlockKey(hash))
 	if err != nil {
 		// TODO(missionliao): Modify the interface to return error.
 		panic(err)
@@ -58,18 +67,25 @@ func (lvl *LevelDBBackedDB) HasBlock(hash common.Hash) bool {
 	return exists
 }
 
+func (lvl *LevelDBBackedDB) internalHasBlock(key []byte) (bool, error) {
+	exists, err := lvl.db.Has(key, nil)
+	if err != nil {
+		return false, err
+	}
+	return exists, nil
+}
+
 // GetBlock implements the Reader.GetBlock method.
 func (lvl *LevelDBBackedDB) GetBlock(
 	hash common.Hash) (block types.Block, err error) {
-
-	queried, err := lvl.db.Get([]byte(hash[:]), nil)
+	queried, err := lvl.db.Get(lvl.getBlockKey(hash), nil)
 	if err != nil {
 		if err == leveldb.ErrNotFound {
 			err = ErrBlockDoesNotExist
 		}
 		return
 	}
-	err = json.Unmarshal(queried, &block)
+	err = rlp.DecodeBytes(queried, &block)
 	if err != nil {
 		return
 	}
@@ -80,20 +96,20 @@ func (lvl *LevelDBBackedDB) GetBlock(
 func (lvl *LevelDBBackedDB) UpdateBlock(block types.Block) (err error) {
 	// NOTE: we didn't handle changes of block hash (and it
 	//       should not happen).
-	marshaled, err := json.Marshal(&block)
+	marshaled, err := rlp.EncodeToBytes(&block)
 	if err != nil {
 		return
 	}
-
-	if !lvl.HasBlock(block.Hash) {
+	blockKey := lvl.getBlockKey(block.Hash)
+	exists, err := lvl.internalHasBlock(blockKey)
+	if err != nil {
+		return
+	}
+	if !exists {
 		err = ErrBlockDoesNotExist
 		return
 	}
-	err = lvl.db.Put(
-		[]byte(block.Hash[:]),
-		marshaled,
-		nil)
-	if err != nil {
+	if err = lvl.db.Put(blockKey, marshaled, nil); err != nil {
 		return
 	}
 	return
@@ -101,19 +117,20 @@ func (lvl *LevelDBBackedDB) UpdateBlock(block types.Block) (err error) {
 
 // PutBlock implements the Writer.PutBlock method.
 func (lvl *LevelDBBackedDB) PutBlock(block types.Block) (err error) {
-	marshaled, err := json.Marshal(&block)
+	marshaled, err := rlp.EncodeToBytes(&block)
+	if err != nil {
+		return
+	}
+	blockKey := lvl.getBlockKey(block.Hash)
+	exists, err := lvl.internalHasBlock(blockKey)
 	if err != nil {
 		return
 	}
-	if lvl.HasBlock(block.Hash) {
+	if exists {
 		err = ErrBlockExists
 		return
 	}
-	err = lvl.db.Put(
-		[]byte(block.Hash[:]),
-		marshaled,
-		nil)
-	if err != nil {
+	if err = lvl.db.Put(blockKey, marshaled, nil); err != nil {
 		return
 	}
 	return
@@ -125,3 +142,62 @@ func (lvl *LevelDBBackedDB) GetAllBlocks() (BlockIterator, error) {
 	// TODO (mission): Implement this part via goleveldb's iterator.
 	return nil, ErrNotImplemented
 }
+
+// PutCompactionChainTipInfo saves tip of compaction chain into the database.
+func (lvl *LevelDBBackedDB) PutCompactionChainTipInfo(
+	blockHash common.Hash, height uint64) error {
+	marshaled, err := rlp.EncodeToBytes(&compactionChainTipInfo{
+		Hash:   blockHash,
+		Height: height,
+	})
+	if err != nil {
+		return err
+	}
+	// Check current cached tip info to make sure the one to be updated is
+	// valid.
+	info, err := lvl.internalGetCompactionChainTipInfo()
+	if err != nil {
+		return err
+	}
+	if info.Height >= height {
+		return ErrInvalidCompactionChainTipHeight
+	}
+	if err = lvl.db.Put(compactionChainTipInfoKey, marshaled, nil); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (lvl *LevelDBBackedDB) internalGetCompactionChainTipInfo() (
+	info compactionChainTipInfo, err error) {
+	queried, err := lvl.db.Get(compactionChainTipInfoKey, nil)
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			err = nil
+		}
+		return
+	}
+	if err = rlp.DecodeBytes(queried, &info); err != nil {
+		return
+	}
+	return
+}
+
+// GetCompactionChainTipInfo get the tip info of compaction chain into the
+// database.
+func (lvl *LevelDBBackedDB) GetCompactionChainTipInfo() (
+	hash common.Hash, height uint64) {
+	info, err := lvl.internalGetCompactionChainTipInfo()
+	if err != nil {
+		panic(err)
+	}
+	hash, height = info.Hash, info.Height
+	return
+}
+
+func (lvl *LevelDBBackedDB) getBlockKey(hash common.Hash) (ret []byte) {
+	ret = make([]byte, len(blockKeyPrefix)+len(hash[:]))
+	copy(ret, blockKeyPrefix)
+	copy(ret[len(blockKeyPrefix):], hash[:])
+	return
+}
diff --git a/core/db/level-db_test.go b/core/db/level-db_test.go
index 1335d5d..69c8f07 100644
--- a/core/db/level-db_test.go
+++ b/core/db/level-db_test.go
@@ -37,12 +37,12 @@ type LevelDBTestSuite struct {
 func (s *LevelDBTestSuite) TestBasicUsage() {
 	dbName := fmt.Sprintf("test-db-%v.db", time.Now().UTC())
 	dbInst, err := NewLevelDBBackedDB(dbName)
-	s.Require().Nil(err)
+	s.Require().NoError(err)
 	defer func(dbName string) {
 		err = dbInst.Close()
-		s.Nil(err)
+		s.NoError(err)
 		err = os.RemoveAll(dbName)
-		s.Nil(err)
+		s.NoError(err)
 	}(dbName)
 
 	// Queried something from an empty database.
@@ -64,11 +64,11 @@ func (s *LevelDBTestSuite) TestBasicUsage() {
 
 	// Put to create a new record should just work fine.
 	err = dbInst.PutBlock(block1)
-	s.Nil(err)
+	s.NoError(err)
 
 	// Get it back should work fine.
 	queried, err := dbInst.GetBlock(block1.Hash)
-	s.Nil(err)
+	s.NoError(err)
 	s.Equal(queried.ProposerID, block1.ProposerID)
 
 	// Test Update.
@@ -76,24 +76,24 @@ func (s *LevelDBTestSuite) TestBasicUsage() {
 	queried.Timestamp = now
 
 	err = dbInst.UpdateBlock(queried)
-	s.Nil(err)
+	s.NoError(err)
 
 	// Try to get it back via NodeID and height.
 	queried, err = dbInst.GetBlock(block1.Hash)
 
-	s.Nil(err)
+	s.NoError(err)
 	s.Equal(now, queried.Timestamp)
 }
 
 func (s *LevelDBTestSuite) TestSyncIndex() {
 	dbName := fmt.Sprintf("test-db-%v-si.db", time.Now().UTC())
 	dbInst, err := NewLevelDBBackedDB(dbName)
-	s.Require().Nil(err)
+	s.Require().NoError(err)
 	defer func(dbName string) {
 		err = dbInst.Close()
-		s.Nil(err)
+		s.NoError(err)
 		err = os.RemoveAll(dbName)
-		s.Nil(err)
+		s.NoError(err)
 	}(dbName)
 
 	// Create some blocks.
@@ -112,21 +112,43 @@ func (s *LevelDBTestSuite) TestSyncIndex() {
 
 	// Save blocks to db.
 	err = dbInst.Close()
-	s.Nil(err)
+	s.NoError(err)
 
 	// Load back blocks(syncIndex is called).
 	dbInst, err = NewLevelDBBackedDB(dbName)
-	s.Require().Nil(err)
+	s.Require().NoError(err)
 
 	// Verify result.
 	for _, block := range blocks {
 		queried, err := dbInst.GetBlock(block.Hash)
-		s.Nil(err)
+		s.NoError(err)
 		s.Equal(block.ProposerID, queried.ProposerID)
 		s.Equal(block.Position.Height, queried.Position.Height)
 	}
 }
 
+func (s *LevelDBTestSuite) TestCompactionChainTipInfo() {
+	dbName := fmt.Sprintf("test-db-%v-cc-tip.db", time.Now().UTC())
+	dbInst, err := NewLevelDBBackedDB(dbName)
+	s.Require().NoError(err)
+	defer func(dbName string) {
+		err = dbInst.Close()
+		s.NoError(err)
+		err = os.RemoveAll(dbName)
+		s.NoError(err)
+	}(dbName)
+	// Save some tip info.
+	hash := common.NewRandomHash()
+	s.Require().NoError(dbInst.PutCompactionChainTipInfo(hash, 123))
+	// Get it back to check.
+	hashBack, height := dbInst.GetCompactionChainTipInfo()
+	s.Require().Equal(hash, hashBack)
+	s.Require().Equal(height, uint64(123))
+	// Unable to put compaction chain tip info with lower height.
+	err = dbInst.PutCompactionChainTipInfo(hash, 122)
+	s.Require().IsType(err, ErrInvalidCompactionChainTipHeight)
+}
+
 func TestLevelDB(t *testing.T) {
 	suite.Run(t, new(LevelDBTestSuite))
 }
diff --git a/core/db/memory.go b/core/db/memory.go
index 4246e4f..568c64b 100644
--- a/core/db/memory.go
+++ b/core/db/memory.go
@@ -41,10 +41,13 @@ func (seq *blockSeqIterator) NextBlock() (types.Block, error) {
 
 // MemBackedDB is a memory backed DB implementation.
 type MemBackedDB struct {
-	blocksMutex        sync.RWMutex
-	blockHashSequence  common.Hashes
-	blocksByHash       map[common.Hash]*types.Block
-	persistantFilePath string
+	blocksLock               sync.RWMutex
+	blockHashSequence        common.Hashes
+	blocksByHash             map[common.Hash]*types.Block
+	compactionChainTipLock   sync.RWMutex
+	compactionChainTipHash   common.Hash
+	compactionChainTipHeight uint64
+	persistantFilePath       string
 }
 
 // NewMemBackedDB initialize a memory-backed database.
@@ -87,8 +90,8 @@ func NewMemBackedDB(persistantFilePath ...string) (
 
 // HasBlock returns wheter or not the DB has a block identified with the hash.
 func (m *MemBackedDB) HasBlock(hash common.Hash) bool {
-	m.blocksMutex.RLock()
-	defer m.blocksMutex.RUnlock()
+	m.blocksLock.RLock()
+	defer m.blocksLock.RUnlock()
 
 	_, ok := m.blocksByHash[hash]
 	return ok
@@ -96,8 +99,8 @@ func (m *MemBackedDB) HasBlock(hash common.Hash) bool {
 
 // GetBlock returns a block given a hash.
 func (m *MemBackedDB) GetBlock(hash common.Hash) (types.Block, error) {
-	m.blocksMutex.RLock()
-	defer m.blocksMutex.RUnlock()
+	m.blocksLock.RLock()
+	defer m.blocksLock.RUnlock()
 
 	return m.internalGetBlock(hash)
 }
@@ -116,8 +119,8 @@ func (m *MemBackedDB) PutBlock(block types.Block) error {
 		return ErrBlockExists
 	}
 
-	m.blocksMutex.Lock()
-	defer m.blocksMutex.Unlock()
+	m.blocksLock.Lock()
+	defer m.blocksLock.Unlock()
 
 	m.blockHashSequence = append(m.blockHashSequence, block.Hash)
 	m.blocksByHash[block.Hash] = &block
@@ -130,13 +133,35 @@ func (m *MemBackedDB) UpdateBlock(block types.Block) error {
 		return ErrBlockDoesNotExist
 	}
 
-	m.blocksMutex.Lock()
-	defer m.blocksMutex.Unlock()
+	m.blocksLock.Lock()
+	defer m.blocksLock.Unlock()
 
 	m.blocksByHash[block.Hash] = &block
 	return nil
 }
 
+// PutCompactionChainTipInfo saves tip of compaction chain into the database.
+func (m *MemBackedDB) PutCompactionChainTipInfo(
+	blockHash common.Hash, height uint64) error {
+	m.compactionChainTipLock.Lock()
+	defer m.compactionChainTipLock.Unlock()
+	if m.compactionChainTipHeight >= height {
+		return ErrInvalidCompactionChainTipHeight
+	}
+	m.compactionChainTipHeight = height
+	m.compactionChainTipHash = blockHash
+	return nil
+}
+
+// GetCompactionChainTipInfo get the tip info of compaction chain into the
+// database.
+func (m *MemBackedDB) GetCompactionChainTipInfo() (
+	hash common.Hash, height uint64) {
+	m.compactionChainTipLock.RLock()
+	defer m.compactionChainTipLock.RUnlock()
+	return m.compactionChainTipHash, m.compactionChainTipHeight
+}
+
 // Close implement Closer interface, which would release allocated resource.
 func (m *MemBackedDB) Close() (err error) {
 	// Save internal state to a pretty-print json file. It's a temporary way
@@ -145,8 +170,8 @@ func (m *MemBackedDB) Close() (err error) {
 		return
 	}
 
-	m.blocksMutex.RLock()
-	defer m.blocksMutex.RUnlock()
+	m.blocksLock.RLock()
+	defer m.blocksLock.RUnlock()
 
 	toDump := struct {
 		Sequence common.Hashes
@@ -167,8 +192,8 @@ func (m *MemBackedDB) Close() (err error) {
 }
 
 func (m *MemBackedDB) getBlockByIndex(idx int) (types.Block, error) {
-	m.blocksMutex.RLock()
-	defer m.blocksMutex.RUnlock()
+	m.blocksLock.RLock()
+	defer m.blocksLock.RUnlock()
 
 	if idx >= len(m.blockHashSequence) {
 		return types.Block{}, ErrIterationFinished
diff --git a/core/db/memory_test.go b/core/db/memory_test.go
index 8fee582..7d18c3a 100644
--- a/core/db/memory_test.go
+++ b/core/db/memory_test.go
@@ -72,55 +72,55 @@ func (s *MemBackedDBTestSuite) TestSaveAndLoad() {
 
 	// Make sure the file pointed by 'dbPath' doesn't exist.
 	_, err := os.Stat(dbPath)
-	s.Require().NotNil(err)
+	s.Require().Error(err)
 
 	dbInst, err := NewMemBackedDB(dbPath)
-	s.Require().Nil(err)
+	s.Require().NoError(err)
 	s.Require().NotNil(dbInst)
 	defer func() {
 		if dbInst != nil {
-			s.Nil(os.Remove(dbPath))
+			s.NoError(os.Remove(dbPath))
 			dbInst = nil
 		}
 	}()
 
-	s.Nil(dbInst.PutBlock(*s.b00))
-	s.Nil(dbInst.PutBlock(*s.b01))
-	s.Nil(dbInst.PutBlock(*s.b02))
-	s.Nil(dbInst.Close())
+	s.NoError(dbInst.PutBlock(*s.b00))
+	s.NoError(dbInst.PutBlock(*s.b01))
+	s.NoError(dbInst.PutBlock(*s.b02))
+	s.NoError(dbInst.Close())
 
 	// Load the json file back to check if all inserted blocks
 	// exists.
 	dbInst, err = NewMemBackedDB(dbPath)
-	s.Require().Nil(err)
+	s.Require().NoError(err)
 	s.Require().NotNil(dbInst)
 	s.True(dbInst.HasBlock(s.b00.Hash))
 	s.True(dbInst.HasBlock(s.b01.Hash))
 	s.True(dbInst.HasBlock(s.b02.Hash))
-	s.Nil(dbInst.Close())
+	s.NoError(dbInst.Close())
 }
 
 func (s *MemBackedDBTestSuite) TestIteration() {
 	// Make sure the file pointed by 'dbPath' doesn't exist.
 	dbInst, err := NewMemBackedDB()
-	s.Require().Nil(err)
+	s.Require().NoError(err)
 	s.Require().NotNil(dbInst)
 
 	// Setup database.
-	s.Nil(dbInst.PutBlock(*s.b00))
-	s.Nil(dbInst.PutBlock(*s.b01))
-	s.Nil(dbInst.PutBlock(*s.b02))
+	s.NoError(dbInst.PutBlock(*s.b00))
+	s.NoError(dbInst.PutBlock(*s.b01))
+	s.NoError(dbInst.PutBlock(*s.b02))
 
 	// Check if we can iterate all 3 blocks.
 	iter, err := dbInst.GetAllBlocks()
-	s.Require().Nil(err)
+	s.Require().NoError(err)
 	touched := common.Hashes{}
 	for {
 		b, err := iter.NextBlock()
 		if err == ErrIterationFinished {
 			break
 		}
-		s.Require().Nil(err)
+		s.Require().NoError(err)
 		touched = append(touched, b.Hash)
 	}
 	s.Len(touched, 3)
@@ -129,6 +129,22 @@ func (s *MemBackedDBTestSuite) TestIteration() {
 	s.Contains(touched, s.b02.Hash)
 }
 
+func (s *MemBackedDBTestSuite) TestCompactionChainTipInfo() {
+	dbInst, err := NewMemBackedDB()
+	s.Require().NoError(err)
+	s.Require().NotNil(dbInst)
+	// Save some tip info.
+	hash := common.NewRandomHash()
+	s.Require().NoError(dbInst.PutCompactionChainTipInfo(hash, 123))
+	// Get it back to check.
+	hashBack, height := dbInst.GetCompactionChainTipInfo()
+	s.Require().Equal(hash, hashBack)
+	s.Require().Equal(height, uint64(123))
+	// Unable to put compaction chain tip info with lower height.
+	err = dbInst.PutCompactionChainTipInfo(hash, 122)
+	s.Require().IsType(err, ErrInvalidCompactionChainTipHeight)
+}
+
 func TestMemBackedDB(t *testing.T) {
 	suite.Run(t, new(MemBackedDBTestSuite))
 }
diff --git a/core/syncer/consensus.go b/core/syncer/consensus.go
index 13a8873..901485e 100644
--- a/core/syncer/consensus.go
+++ b/core/syncer/consensus.go
@@ -42,6 +42,10 @@ var (
 	// ErrMismatchBlockHashSequence means the delivering sequence is not
 	// correct, compared to finalized blocks.
 	ErrMismatchBlockHashSequence = fmt.Errorf("mismatch block hash sequence")
+	// ErrInvalidSyncingFinalizationHeight raised when the blocks to sync is
+	// not following the compaction chain tip in database.
+	ErrInvalidSyncingFinalizationHeight = fmt.Errorf(
+		"invalid syncing finalization height")
 )
 
 // Consensus is for syncing consensus module.
@@ -394,6 +398,15 @@ func (con *Consensus) SyncBlocks(
 			return nil, ErrInvalidBlockOrder
 		}
 	}
+	// Make sure the first block is the next block of current compaction chain
+	// tip in DB.
+	_, tipHeight := con.db.GetCompactionChainTipInfo()
+	if blocks[0].Finalization.Height != tipHeight+1 {
+		con.logger.Error("mismatched finalization height",
+			"now", blocks[0].Finalization.Height,
+			"expected", tipHeight+1)
+		return nil, ErrInvalidSyncingFinalizationHeight
+	}
 	con.logger.Info("syncBlocks",
 		"position", &blocks[0].Position,
 		"final height", blocks[0].Finalization.Height,
@@ -404,10 +417,19 @@ func (con *Consensus) SyncBlocks(
 	for _, b := range blocks {
 		// TODO(haoping) remove this if lattice puts blocks into db.
 		if err := con.db.PutBlock(*b); err != nil {
-			if err != db.ErrBlockExists {
+			// A block might be put into db when confirmed by BA, but not
+			// finalized yet.
+			if err == db.ErrBlockExists {
+				err = con.db.UpdateBlock(*b)
+			}
+			if err != nil {
 				return nil, err
 			}
 		}
+		if err := con.db.PutCompactionChainTipInfo(
+			b.Hash, b.Finalization.Height); err != nil {
+			return nil, err
+		}
 		if err := con.processFinalizedBlock(b); err != nil {
 			return nil, err
 		}
diff --git a/core/test/blocks-generator_test.go b/core/test/blocks-generator_test.go
index bd7a5a2..78b609b 100644
--- a/core/test/blocks-generator_test.go
+++ b/core/test/blocks-generator_test.go
@@ -18,7 +18,6 @@
 package test
 
 import (
-	"fmt"
 	"sort"
 	"testing"
 	"time"
@@ -318,7 +317,6 @@ func (s *BlocksGeneratorTestSuite) TestConcateBlocksFromRounds() {
 		totalAckCount += len(b.Acks)
 	}
 	// At least all blocks can ack some non-parent block.
-	fmt.Println(totalAckCount, totalBlockCount)
 	req.True(totalAckCount/totalBlockCount >= 2)
 }
 
diff --git a/core/test/utils.go b/core/test/utils.go
index 56c5eac..6abd0b5 100644
--- a/core/test/utils.go
+++ b/core/test/utils.go
@@ -18,6 +18,7 @@
 package test
 
 import (
+	"errors"
 	"fmt"
 	"math"
 	"net"
@@ -26,6 +27,7 @@ import (
 	"github.com/dexon-foundation/dexon-consensus/common"
 	"github.com/dexon-foundation/dexon-consensus/core/crypto"
 	"github.com/dexon-foundation/dexon-consensus/core/crypto/ecdsa"
+	"github.com/dexon-foundation/dexon-consensus/core/db"
 	"github.com/dexon-foundation/dexon-consensus/core/types"
 	typesDKG "github.com/dexon-foundation/dexon-consensus/core/types/dkg"
 	"github.com/dexon-foundation/dexon/rlp"
@@ -170,3 +172,32 @@ func cloneBlockRandomnessResult(rand *types.BlockRandomnessResult) (
 	}
 	return
 }
+
+var (
+	// ErrCompactionChainTipBlockNotExists raised when the hash of compaction
+	// chain tip doesn't match a block in database.
+	ErrCompactionChainTipBlockNotExists = errors.New(
+		"compaction chain tip block not exists")
+	// ErrEmptyCompactionChainTipInfo raised when a compaction chain tip info
+	// is empty.
+	ErrEmptyCompactionChainTipInfo = errors.New(
+		"empty compaction chain tip info")
+	// ErrMismatchBlockHash raise when the hash for that block mismatched.
+	ErrMismatchBlockHash = errors.New("mismatched block hash")
+)
+
+// VerifyDB check if a database is valid after test.
+func VerifyDB(db db.Database) error {
+	hash, height := db.GetCompactionChainTipInfo()
+	if (hash == common.Hash{}) || height == 0 {
+		return ErrEmptyCompactionChainTipInfo
+	}
+	b, err := db.GetBlock(hash)
+	if err != nil {
+		return err
+	}
+	if b.Hash != hash {
+		return ErrMismatchBlockHash
+	}
+	return nil
+}