From 8c4dab77ba48dc68073fe1df79e7000043c0f966 Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@twurst.com>
Date: Mon, 14 Sep 2015 09:35:57 +0200
Subject: [PATCH 1/4] all: move common.Database to package ethdb

---
 cmd/geth/blocktestcmd.go           |  3 +-
 cmd/geth/chaincmd.go               |  3 +-
 cmd/geth/js_test.go                |  2 +-
 cmd/utils/flags.go                 |  2 +-
 common/natspec/natspec_e2e_test.go |  2 +-
 core/bench_test.go                 |  2 +-
 core/block_processor.go            |  5 ++--
 core/chain_makers.go               |  7 +++--
 core/chain_manager.go              |  5 ++--
 core/chain_manager_test.go         |  4 +--
 core/chain_util.go                 | 45 +++++++++++++++---------------
 core/genesis.go                    |  9 +++---
 core/helper_test.go                |  6 ++--
 core/manager.go                    |  6 ++--
 core/state/state_object.go         |  7 +++--
 core/state/statedb.go              |  5 ++--
 core/transaction_util.go           | 10 +++----
 eth/backend.go                     | 16 +++++------
 eth/handler.go                     |  5 ++--
 common/db.go => ethdb/interface.go |  3 +-
 miner/agent.go                     |  5 ++--
 miner/worker.go                    |  3 +-
 tests/block_test_util.go           |  2 +-
 tests/util.go                      |  3 +-
 24 files changed, 85 insertions(+), 75 deletions(-)
 rename common/db.go => ethdb/interface.go (96%)

diff --git a/cmd/geth/blocktestcmd.go b/cmd/geth/blocktestcmd.go
index 4eff82e3d..a667cfd60 100644
--- a/cmd/geth/blocktestcmd.go
+++ b/cmd/geth/blocktestcmd.go
@@ -22,7 +22,6 @@ import (
 
 	"github.com/codegangsta/cli"
 	"github.com/ethereum/go-ethereum/cmd/utils"
-	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/eth"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/tests"
@@ -103,7 +102,7 @@ func runBlockTest(ctx *cli.Context) {
 
 func runOneBlockTest(ctx *cli.Context, test *tests.BlockTest) (*eth.Ethereum, error) {
 	cfg := utils.MakeEthConfig(ClientIdentifier, Version, ctx)
-	cfg.NewDB = func(path string) (common.Database, error) { return ethdb.NewMemDatabase() }
+	cfg.NewDB = func(path string) (ethdb.Database, error) { return ethdb.NewMemDatabase() }
 	cfg.MaxPeers = 0 // disable network
 	cfg.Shh = false  // disable whisper
 	cfg.NAT = nil    // disable port mapping
diff --git a/cmd/geth/chaincmd.go b/cmd/geth/chaincmd.go
index c42045918..c5bc4b66a 100644
--- a/cmd/geth/chaincmd.go
+++ b/cmd/geth/chaincmd.go
@@ -29,6 +29,7 @@ import (
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/logger/glog"
 )
 
@@ -191,7 +192,7 @@ func hashish(x string) bool {
 	return err != nil
 }
 
-func closeAll(dbs ...common.Database) {
+func closeAll(dbs ...ethdb.Database) {
 	for _, db := range dbs {
 		db.Close()
 	}
diff --git a/cmd/geth/js_test.go b/cmd/geth/js_test.go
index 67c36dfe7..2fd5a531d 100644
--- a/cmd/geth/js_test.go
+++ b/cmd/geth/js_test.go
@@ -103,7 +103,7 @@ func testREPL(t *testing.T, config func(*eth.Config)) (string, *testjethre, *eth
 		Name:           "test",
 		SolcPath:       testSolcPath,
 		PowTest:        true,
-		NewDB:          func(path string) (common.Database, error) { return db, nil },
+		NewDB:          func(path string) (ethdb.Database, error) { return db, nil },
 	}
 	if config != nil {
 		config(conf)
diff --git a/cmd/utils/flags.go b/cmd/utils/flags.go
index 95fb649e6..b45ef0af2 100644
--- a/cmd/utils/flags.go
+++ b/cmd/utils/flags.go
@@ -508,7 +508,7 @@ func SetupEth(ctx *cli.Context) {
 }
 
 // MakeChain creates a chain manager from set command line flags.
-func MakeChain(ctx *cli.Context) (chain *core.ChainManager, chainDb common.Database) {
+func MakeChain(ctx *cli.Context) (chain *core.ChainManager, chainDb ethdb.Database) {
 	datadir := ctx.GlobalString(DataDirFlag.Name)
 	cache := ctx.GlobalInt(CacheFlag.Name)
 
diff --git a/common/natspec/natspec_e2e_test.go b/common/natspec/natspec_e2e_test.go
index fc8ca6af2..ea28b457e 100644
--- a/common/natspec/natspec_e2e_test.go
+++ b/common/natspec/natspec_e2e_test.go
@@ -143,7 +143,7 @@ func testEth(t *testing.T) (ethereum *eth.Ethereum, err error) {
 		MaxPeers:       0,
 		PowTest:        true,
 		Etherbase:      common.HexToAddress(testAddress),
-		NewDB:          func(path string) (common.Database, error) { return db, nil },
+		NewDB:          func(path string) (ethdb.Database, error) { return db, nil },
 	})
 
 	if err != nil {
diff --git a/core/bench_test.go b/core/bench_test.go
index baae8a7a5..d05b7d30b 100644
--- a/core/bench_test.go
+++ b/core/bench_test.go
@@ -144,7 +144,7 @@ func genUncles(i int, gen *BlockGen) {
 
 func benchInsertChain(b *testing.B, disk bool, gen func(int, *BlockGen)) {
 	// Create the database in memory or in a temporary directory.
-	var db common.Database
+	var db ethdb.Database
 	if !disk {
 		db, _ = ethdb.NewMemDatabase()
 	} else {
diff --git a/core/block_processor.go b/core/block_processor.go
index 1238fda7b..1d3bc6656 100644
--- a/core/block_processor.go
+++ b/core/block_processor.go
@@ -26,6 +26,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
@@ -41,7 +42,7 @@ const (
 )
 
 type BlockProcessor struct {
-	chainDb common.Database
+	chainDb ethdb.Database
 	// Mutex for locking the block processor. Blocks can only be handled one at a time
 	mutex sync.Mutex
 	// Canonical block chain
@@ -68,7 +69,7 @@ type GasPool interface {
 	SubGas(gas, price *big.Int) error
 }
 
-func NewBlockProcessor(db common.Database, pow pow.PoW, chainManager *ChainManager, eventMux *event.TypeMux) *BlockProcessor {
+func NewBlockProcessor(db ethdb.Database, pow pow.PoW, chainManager *ChainManager, eventMux *event.TypeMux) *BlockProcessor {
 	sm := &BlockProcessor{
 		chainDb:  db,
 		mem:      make(map[string]*big.Int),
diff --git a/core/chain_makers.go b/core/chain_makers.go
index f89218f82..d3b7c42b6 100644
--- a/core/chain_makers.go
+++ b/core/chain_makers.go
@@ -22,6 +22,7 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/pow"
 )
@@ -142,7 +143,7 @@ func (b *BlockGen) PrevBlock(index int) *types.Block {
 // Blocks created by GenerateChain do not contain valid proof of work
 // values. Inserting them into ChainManager requires use of FakePow or
 // a similar non-validating proof of work implementation.
-func GenerateChain(parent *types.Block, db common.Database, n int, gen func(int, *BlockGen)) []*types.Block {
+func GenerateChain(parent *types.Block, db ethdb.Database, n int, gen func(int, *BlockGen)) []*types.Block {
 	statedb := state.New(parent.Root(), db)
 	blocks := make(types.Blocks, n)
 	genblock := func(i int, h *types.Header) *types.Block {
@@ -185,7 +186,7 @@ func makeHeader(parent *types.Block, state *state.StateDB) *types.Header {
 
 // newCanonical creates a new deterministic canonical chain by running
 // InsertChain on the result of makeChain.
-func newCanonical(n int, db common.Database) (*BlockProcessor, error) {
+func newCanonical(n int, db ethdb.Database) (*BlockProcessor, error) {
 	evmux := &event.TypeMux{}
 
 	WriteTestNetGenesisBlock(db, 0)
@@ -201,7 +202,7 @@ func newCanonical(n int, db common.Database) (*BlockProcessor, error) {
 	return bman, err
 }
 
-func makeChain(parent *types.Block, n int, db common.Database, seed int) []*types.Block {
+func makeChain(parent *types.Block, n int, db ethdb.Database, seed int) []*types.Block {
 	return GenerateChain(parent, db, n, func(i int, b *BlockGen) {
 		b.SetCoinbase(common.Address{0: byte(seed), 19: byte(i)})
 	})
diff --git a/core/chain_manager.go b/core/chain_manager.go
index 407945f8e..1218b1a6e 100644
--- a/core/chain_manager.go
+++ b/core/chain_manager.go
@@ -30,6 +30,7 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
@@ -60,7 +61,7 @@ const (
 
 type ChainManager struct {
 	//eth          EthManager
-	chainDb      common.Database
+	chainDb      ethdb.Database
 	processor    types.BlockProcessor
 	eventMux     *event.TypeMux
 	genesisBlock *types.Block
@@ -90,7 +91,7 @@ type ChainManager struct {
 	pow pow.PoW
 }
 
-func NewChainManager(chainDb common.Database, pow pow.PoW, mux *event.TypeMux) (*ChainManager, error) {
+func NewChainManager(chainDb ethdb.Database, pow pow.PoW, mux *event.TypeMux) (*ChainManager, error) {
 	headerCache, _ := lru.New(headerCacheLimit)
 	bodyCache, _ := lru.New(bodyCacheLimit)
 	bodyRLPCache, _ := lru.New(bodyCacheLimit)
diff --git a/core/chain_manager_test.go b/core/chain_manager_test.go
index a20480de8..67ca41f00 100644
--- a/core/chain_manager_test.go
+++ b/core/chain_manager_test.go
@@ -46,7 +46,7 @@ func thePow() pow.PoW {
 	return pow
 }
 
-func theChainManager(db common.Database, t *testing.T) *ChainManager {
+func theChainManager(db ethdb.Database, t *testing.T) *ChainManager {
 	var eventMux event.TypeMux
 	WriteTestNetGenesisBlock(db, 0)
 	chainMan, err := NewChainManager(db, thePow(), &eventMux)
@@ -380,7 +380,7 @@ func makeChainWithDiff(genesis *types.Block, d []int, seed byte) []*types.Block
 	return chain
 }
 
-func chm(genesis *types.Block, db common.Database) *ChainManager {
+func chm(genesis *types.Block, db ethdb.Database) *ChainManager {
 	var eventMux event.TypeMux
 	bc := &ChainManager{chainDb: db, genesisBlock: genesis, eventMux: &eventMux, pow: FakePow{}}
 	bc.headerCache, _ = lru.New(100)
diff --git a/core/chain_util.go b/core/chain_util.go
index 0e3fa31f9..33d94cebd 100644
--- a/core/chain_util.go
+++ b/core/chain_util.go
@@ -22,6 +22,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
 	"github.com/ethereum/go-ethereum/params"
@@ -111,7 +112,7 @@ func CalcGasLimit(parent *types.Block) *big.Int {
 }
 
 // GetCanonicalHash retrieves a hash assigned to a canonical block number.
-func GetCanonicalHash(db common.Database, number uint64) common.Hash {
+func GetCanonicalHash(db ethdb.Database, number uint64) common.Hash {
 	data, _ := db.Get(append(blockNumPrefix, big.NewInt(int64(number)).Bytes()...))
 	if len(data) == 0 {
 		return common.Hash{}
@@ -124,7 +125,7 @@ func GetCanonicalHash(db common.Database, number uint64) common.Hash {
 // last block hash is only updated upon a full block import, the last header
 // hash is updated already at header import, allowing head tracking for the
 // fast synchronization mechanism.
-func GetHeadHeaderHash(db common.Database) common.Hash {
+func GetHeadHeaderHash(db ethdb.Database) common.Hash {
 	data, _ := db.Get(headHeaderKey)
 	if len(data) == 0 {
 		return common.Hash{}
@@ -133,7 +134,7 @@ func GetHeadHeaderHash(db common.Database) common.Hash {
 }
 
 // GetHeadBlockHash retrieves the hash of the current canonical head block.
-func GetHeadBlockHash(db common.Database) common.Hash {
+func GetHeadBlockHash(db ethdb.Database) common.Hash {
 	data, _ := db.Get(headBlockKey)
 	if len(data) == 0 {
 		return common.Hash{}
@@ -143,14 +144,14 @@ func GetHeadBlockHash(db common.Database) common.Hash {
 
 // GetHeaderRLP retrieves a block header in its raw RLP database encoding, or nil
 // if the header's not found.
-func GetHeaderRLP(db common.Database, hash common.Hash) rlp.RawValue {
+func GetHeaderRLP(db ethdb.Database, hash common.Hash) rlp.RawValue {
 	data, _ := db.Get(append(append(blockPrefix, hash[:]...), headerSuffix...))
 	return data
 }
 
 // GetHeader retrieves the block header corresponding to the hash, nil if none
 // found.
-func GetHeader(db common.Database, hash common.Hash) *types.Header {
+func GetHeader(db ethdb.Database, hash common.Hash) *types.Header {
 	data := GetHeaderRLP(db, hash)
 	if len(data) == 0 {
 		return nil
@@ -164,14 +165,14 @@ func GetHeader(db common.Database, hash common.Hash) *types.Header {
 }
 
 // GetBodyRLP retrieves the block body (transactions and uncles) in RLP encoding.
-func GetBodyRLP(db common.Database, hash common.Hash) rlp.RawValue {
+func GetBodyRLP(db ethdb.Database, hash common.Hash) rlp.RawValue {
 	data, _ := db.Get(append(append(blockPrefix, hash[:]...), bodySuffix...))
 	return data
 }
 
 // GetBody retrieves the block body (transactons, uncles) corresponding to the
 // hash, nil if none found.
-func GetBody(db common.Database, hash common.Hash) *types.Body {
+func GetBody(db ethdb.Database, hash common.Hash) *types.Body {
 	data := GetBodyRLP(db, hash)
 	if len(data) == 0 {
 		return nil
@@ -186,7 +187,7 @@ func GetBody(db common.Database, hash common.Hash) *types.Body {
 
 // GetTd retrieves a block's total difficulty corresponding to the hash, nil if
 // none found.
-func GetTd(db common.Database, hash common.Hash) *big.Int {
+func GetTd(db ethdb.Database, hash common.Hash) *big.Int {
 	data, _ := db.Get(append(append(blockPrefix, hash.Bytes()...), tdSuffix...))
 	if len(data) == 0 {
 		return nil
@@ -201,7 +202,7 @@ func GetTd(db common.Database, hash common.Hash) *big.Int {
 
 // GetBlock retrieves an entire block corresponding to the hash, assembling it
 // back from the stored header and body.
-func GetBlock(db common.Database, hash common.Hash) *types.Block {
+func GetBlock(db ethdb.Database, hash common.Hash) *types.Block {
 	// Retrieve the block header and body contents
 	header := GetHeader(db, hash)
 	if header == nil {
@@ -216,7 +217,7 @@ func GetBlock(db common.Database, hash common.Hash) *types.Block {
 }
 
 // WriteCanonicalHash stores the canonical hash for the given block number.
-func WriteCanonicalHash(db common.Database, hash common.Hash, number uint64) error {
+func WriteCanonicalHash(db ethdb.Database, hash common.Hash, number uint64) error {
 	key := append(blockNumPrefix, big.NewInt(int64(number)).Bytes()...)
 	if err := db.Put(key, hash.Bytes()); err != nil {
 		glog.Fatalf("failed to store number to hash mapping into database: %v", err)
@@ -226,7 +227,7 @@ func WriteCanonicalHash(db common.Database, hash common.Hash, number uint64) err
 }
 
 // WriteHeadHeaderHash stores the head header's hash.
-func WriteHeadHeaderHash(db common.Database, hash common.Hash) error {
+func WriteHeadHeaderHash(db ethdb.Database, hash common.Hash) error {
 	if err := db.Put(headHeaderKey, hash.Bytes()); err != nil {
 		glog.Fatalf("failed to store last header's hash into database: %v", err)
 		return err
@@ -235,7 +236,7 @@ func WriteHeadHeaderHash(db common.Database, hash common.Hash) error {
 }
 
 // WriteHeadBlockHash stores the head block's hash.
-func WriteHeadBlockHash(db common.Database, hash common.Hash) error {
+func WriteHeadBlockHash(db ethdb.Database, hash common.Hash) error {
 	if err := db.Put(headBlockKey, hash.Bytes()); err != nil {
 		glog.Fatalf("failed to store last block's hash into database: %v", err)
 		return err
@@ -244,7 +245,7 @@ func WriteHeadBlockHash(db common.Database, hash common.Hash) error {
 }
 
 // WriteHeader serializes a block header into the database.
-func WriteHeader(db common.Database, header *types.Header) error {
+func WriteHeader(db ethdb.Database, header *types.Header) error {
 	data, err := rlp.EncodeToBytes(header)
 	if err != nil {
 		return err
@@ -259,7 +260,7 @@ func WriteHeader(db common.Database, header *types.Header) error {
 }
 
 // WriteBody serializes the body of a block into the database.
-func WriteBody(db common.Database, hash common.Hash, body *types.Body) error {
+func WriteBody(db ethdb.Database, hash common.Hash, body *types.Body) error {
 	data, err := rlp.EncodeToBytes(body)
 	if err != nil {
 		return err
@@ -274,7 +275,7 @@ func WriteBody(db common.Database, hash common.Hash, body *types.Body) error {
 }
 
 // WriteTd serializes the total difficulty of a block into the database.
-func WriteTd(db common.Database, hash common.Hash, td *big.Int) error {
+func WriteTd(db ethdb.Database, hash common.Hash, td *big.Int) error {
 	data, err := rlp.EncodeToBytes(td)
 	if err != nil {
 		return err
@@ -289,7 +290,7 @@ func WriteTd(db common.Database, hash common.Hash, td *big.Int) error {
 }
 
 // WriteBlock serializes a block into the database, header and body separately.
-func WriteBlock(db common.Database, block *types.Block) error {
+func WriteBlock(db ethdb.Database, block *types.Block) error {
 	// Store the body first to retain database consistency
 	if err := WriteBody(db, block.Hash(), &types.Body{block.Transactions(), block.Uncles()}); err != nil {
 		return err
@@ -302,27 +303,27 @@ func WriteBlock(db common.Database, block *types.Block) error {
 }
 
 // DeleteCanonicalHash removes the number to hash canonical mapping.
-func DeleteCanonicalHash(db common.Database, number uint64) {
+func DeleteCanonicalHash(db ethdb.Database, number uint64) {
 	db.Delete(append(blockNumPrefix, big.NewInt(int64(number)).Bytes()...))
 }
 
 // DeleteHeader removes all block header data associated with a hash.
-func DeleteHeader(db common.Database, hash common.Hash) {
+func DeleteHeader(db ethdb.Database, hash common.Hash) {
 	db.Delete(append(append(blockPrefix, hash.Bytes()...), headerSuffix...))
 }
 
 // DeleteBody removes all block body data associated with a hash.
-func DeleteBody(db common.Database, hash common.Hash) {
+func DeleteBody(db ethdb.Database, hash common.Hash) {
 	db.Delete(append(append(blockPrefix, hash.Bytes()...), bodySuffix...))
 }
 
 // DeleteTd removes all block total difficulty data associated with a hash.
-func DeleteTd(db common.Database, hash common.Hash) {
+func DeleteTd(db ethdb.Database, hash common.Hash) {
 	db.Delete(append(append(blockPrefix, hash.Bytes()...), tdSuffix...))
 }
 
 // DeleteBlock removes all block data associated with a hash.
-func DeleteBlock(db common.Database, hash common.Hash) {
+func DeleteBlock(db ethdb.Database, hash common.Hash) {
 	DeleteHeader(db, hash)
 	DeleteBody(db, hash)
 	DeleteTd(db, hash)
@@ -333,7 +334,7 @@ func DeleteBlock(db common.Database, hash common.Hash) {
 // or nil if not found. This method is only used by the upgrade mechanism to
 // access the old combined block representation. It will be dropped after the
 // network transitions to eth/63.
-func GetBlockByHashOld(db common.Database, hash common.Hash) *types.Block {
+func GetBlockByHashOld(db ethdb.Database, hash common.Hash) *types.Block {
 	data, _ := db.Get(append(blockHashPre, hash[:]...))
 	if len(data) == 0 {
 		return nil
diff --git a/core/genesis.go b/core/genesis.go
index 3a8f0af0c..727e2c75f 100644
--- a/core/genesis.go
+++ b/core/genesis.go
@@ -27,13 +27,14 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
 	"github.com/ethereum/go-ethereum/params"
 )
 
 // WriteGenesisBlock writes the genesis block to the database as block number 0
-func WriteGenesisBlock(chainDb common.Database, reader io.Reader) (*types.Block, error) {
+func WriteGenesisBlock(chainDb ethdb.Database, reader io.Reader) (*types.Block, error) {
 	contents, err := ioutil.ReadAll(reader)
 	if err != nil {
 		return nil, err
@@ -110,7 +111,7 @@ func WriteGenesisBlock(chainDb common.Database, reader io.Reader) (*types.Block,
 
 // GenesisBlockForTesting creates a block in which addr has the given wei balance.
 // The state trie of the block is written to db.
-func GenesisBlockForTesting(db common.Database, addr common.Address, balance *big.Int) *types.Block {
+func GenesisBlockForTesting(db ethdb.Database, addr common.Address, balance *big.Int) *types.Block {
 	statedb := state.New(common.Hash{}, db)
 	obj := statedb.GetOrNewStateObject(addr)
 	obj.SetBalance(balance)
@@ -124,7 +125,7 @@ func GenesisBlockForTesting(db common.Database, addr common.Address, balance *bi
 	return block
 }
 
-func WriteGenesisBlockForTesting(db common.Database, addr common.Address, balance *big.Int) *types.Block {
+func WriteGenesisBlockForTesting(db ethdb.Database, addr common.Address, balance *big.Int) *types.Block {
 	testGenesis := fmt.Sprintf(`{
 	"nonce":"0x%x",
 	"gasLimit":"0x%x",
@@ -137,7 +138,7 @@ func WriteGenesisBlockForTesting(db common.Database, addr common.Address, balanc
 	return block
 }
 
-func WriteTestNetGenesisBlock(chainDb common.Database, nonce uint64) (*types.Block, error) {
+func WriteTestNetGenesisBlock(chainDb ethdb.Database, nonce uint64) (*types.Block, error) {
 	testGenesis := fmt.Sprintf(`{
 	"nonce":"0x%x",
 	"gasLimit":"0x%x",
diff --git a/core/helper_test.go b/core/helper_test.go
index b21f31d7c..81ea6fc22 100644
--- a/core/helper_test.go
+++ b/core/helper_test.go
@@ -22,7 +22,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/core/types"
 	// "github.com/ethereum/go-ethereum/crypto"
-	"github.com/ethereum/go-ethereum/common"
+
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 )
@@ -32,7 +32,7 @@ type TestManager struct {
 	// stateManager *StateManager
 	eventMux *event.TypeMux
 
-	db         common.Database
+	db         ethdb.Database
 	txPool     *TxPool
 	blockChain *ChainManager
 	Blocks     []*types.Block
@@ -74,7 +74,7 @@ func (tm *TestManager) EventMux() *event.TypeMux {
 // 	return nil
 // }
 
-func (tm *TestManager) Db() common.Database {
+func (tm *TestManager) Db() ethdb.Database {
 	return tm.db
 }
 
diff --git a/core/manager.go b/core/manager.go
index 8b0401b03..0f108a6de 100644
--- a/core/manager.go
+++ b/core/manager.go
@@ -18,7 +18,7 @@ package core
 
 import (
 	"github.com/ethereum/go-ethereum/accounts"
-	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 )
 
@@ -28,7 +28,7 @@ type Backend interface {
 	BlockProcessor() *BlockProcessor
 	ChainManager() *ChainManager
 	TxPool() *TxPool
-	ChainDb() common.Database
-	DappDb() common.Database
+	ChainDb() ethdb.Database
+	DappDb() ethdb.Database
 	EventMux() *event.TypeMux
 }
diff --git a/core/state/state_object.go b/core/state/state_object.go
index 69c64ae40..353f2357b 100644
--- a/core/state/state_object.go
+++ b/core/state/state_object.go
@@ -23,6 +23,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
 	"github.com/ethereum/go-ethereum/rlp"
@@ -56,7 +57,7 @@ func (self Storage) Copy() Storage {
 
 type StateObject struct {
 	// State database for storing state changes
-	db   common.Database
+	db   ethdb.Database
 	trie *trie.SecureTrie
 
 	// Address belonging to this account
@@ -87,7 +88,7 @@ type StateObject struct {
 	dirty   bool
 }
 
-func NewStateObject(address common.Address, db common.Database) *StateObject {
+func NewStateObject(address common.Address, db ethdb.Database) *StateObject {
 	object := &StateObject{db: db, address: address, balance: new(big.Int), gasPool: new(big.Int), dirty: true}
 	object.trie = trie.NewSecure((common.Hash{}).Bytes(), db)
 	object.storage = make(Storage)
@@ -96,7 +97,7 @@ func NewStateObject(address common.Address, db common.Database) *StateObject {
 	return object
 }
 
-func NewStateObjectFromBytes(address common.Address, data []byte, db common.Database) *StateObject {
+func NewStateObjectFromBytes(address common.Address, data []byte, db ethdb.Database) *StateObject {
 	// TODO clean me up
 	var extobject struct {
 		Nonce    uint64
diff --git a/core/state/statedb.go b/core/state/statedb.go
index b754f0887..24f97e32a 100644
--- a/core/state/statedb.go
+++ b/core/state/statedb.go
@@ -21,6 +21,7 @@ import (
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
 	"github.com/ethereum/go-ethereum/trie"
@@ -32,7 +33,7 @@ import (
 // * Contracts
 // * Accounts
 type StateDB struct {
-	db   common.Database
+	db   ethdb.Database
 	trie *trie.SecureTrie
 	root common.Hash
 
@@ -47,7 +48,7 @@ type StateDB struct {
 }
 
 // Create a new state from a given trie
-func New(root common.Hash, db common.Database) *StateDB {
+func New(root common.Hash, db ethdb.Database) *StateDB {
 	trie := trie.NewSecure(root[:], db)
 	return &StateDB{root: root, db: db, trie: trie, stateObjects: make(map[string]*StateObject), refund: new(big.Int), logs: make(map[common.Hash]Logs)}
 }
diff --git a/core/transaction_util.go b/core/transaction_util.go
index ce2ceac46..69c6bc36f 100644
--- a/core/transaction_util.go
+++ b/core/transaction_util.go
@@ -32,7 +32,7 @@ var (
 )
 
 // PutTransactions stores the transactions in the given database
-func PutTransactions(db common.Database, block *types.Block, txs types.Transactions) {
+func PutTransactions(db ethdb.Database, block *types.Block, txs types.Transactions) {
 	batch := new(leveldb.Batch)
 	_, batchWrite := db.(*ethdb.LDBDatabase)
 
@@ -78,7 +78,7 @@ func PutTransactions(db common.Database, block *types.Block, txs types.Transacti
 }
 
 // PutReceipts stores the receipts in the current database
-func PutReceipts(db common.Database, receipts types.Receipts) error {
+func PutReceipts(db ethdb.Database, receipts types.Receipts) error {
 	batch := new(leveldb.Batch)
 	_, batchWrite := db.(*ethdb.LDBDatabase)
 
@@ -108,7 +108,7 @@ func PutReceipts(db common.Database, receipts types.Receipts) error {
 }
 
 // GetReceipt returns a receipt by hash
-func GetReceipt(db common.Database, txHash common.Hash) *types.Receipt {
+func GetReceipt(db ethdb.Database, txHash common.Hash) *types.Receipt {
 	data, _ := db.Get(append(receiptsPre, txHash[:]...))
 	if len(data) == 0 {
 		return nil
@@ -124,7 +124,7 @@ func GetReceipt(db common.Database, txHash common.Hash) *types.Receipt {
 
 // GetBlockReceipts returns the receipts generated by the transactions
 // included in block's given hash.
-func GetBlockReceipts(db common.Database, hash common.Hash) types.Receipts {
+func GetBlockReceipts(db ethdb.Database, hash common.Hash) types.Receipts {
 	data, _ := db.Get(append(blockReceiptsPre, hash[:]...))
 	if len(data) == 0 {
 		return nil
@@ -141,7 +141,7 @@ func GetBlockReceipts(db common.Database, hash common.Hash) types.Receipts {
 // PutBlockReceipts stores the block's transactions associated receipts
 // and stores them by block hash in a single slice. This is required for
 // forks and chain reorgs
-func PutBlockReceipts(db common.Database, block *types.Block, receipts types.Receipts) error {
+func PutBlockReceipts(db ethdb.Database, block *types.Block, receipts types.Receipts) error {
 	rs := make([]*types.ReceiptForStorage, len(receipts))
 	for i, receipt := range receipts {
 		rs[i] = (*types.ReceiptForStorage)(receipt)
diff --git a/eth/backend.go b/eth/backend.go
index deb6d3d0f..a923cfa78 100644
--- a/eth/backend.go
+++ b/eth/backend.go
@@ -128,7 +128,7 @@ type Config struct {
 
 	// NewDB is used to create databases.
 	// If nil, the default is to create leveldb databases on disk.
-	NewDB func(path string) (common.Database, error)
+	NewDB func(path string) (ethdb.Database, error)
 }
 
 func (cfg *Config) parseBootNodes() []*discover.Node {
@@ -210,8 +210,8 @@ type Ethereum struct {
 	shutdownChan chan bool
 
 	// DB interfaces
-	chainDb common.Database // Block chain databe
-	dappDb  common.Database // Dapp database
+	chainDb ethdb.Database // Block chain database
+	dappDb  ethdb.Database // Dapp database
 
 	// Closed when databases are flushed and closed
 	databasesClosed chan bool
@@ -267,7 +267,7 @@ func New(config *Config) (*Ethereum, error) {
 
 	newdb := config.NewDB
 	if newdb == nil {
-		newdb = func(path string) (common.Database, error) { return ethdb.NewLDBDatabase(path, config.DatabaseCache) }
+		newdb = func(path string) (ethdb.Database, error) { return ethdb.NewLDBDatabase(path, config.DatabaseCache) }
 	}
 
 	// Open the chain database and perform any upgrades needed
@@ -527,8 +527,8 @@ func (s *Ethereum) BlockProcessor() *core.BlockProcessor { return s.blockProcess
 func (s *Ethereum) TxPool() *core.TxPool                 { return s.txPool }
 func (s *Ethereum) Whisper() *whisper.Whisper            { return s.whisper }
 func (s *Ethereum) EventMux() *event.TypeMux             { return s.eventMux }
-func (s *Ethereum) ChainDb() common.Database             { return s.chainDb }
-func (s *Ethereum) DappDb() common.Database              { return s.dappDb }
+func (s *Ethereum) ChainDb() ethdb.Database              { return s.chainDb }
+func (s *Ethereum) DappDb() ethdb.Database               { return s.dappDb }
 func (s *Ethereum) IsListening() bool                    { return true } // Always listening
 func (s *Ethereum) PeerCount() int                       { return s.net.PeerCount() }
 func (s *Ethereum) Peers() []*p2p.Peer                   { return s.net.Peers() }
@@ -717,7 +717,7 @@ func dagFiles(epoch uint64) (string, string) {
 	return dag, "full-R" + dag
 }
 
-func saveBlockchainVersion(db common.Database, bcVersion int) {
+func saveBlockchainVersion(db ethdb.Database, bcVersion int) {
 	d, _ := db.Get([]byte("BlockchainVersion"))
 	blockchainVersion := common.NewValue(d).Uint()
 
@@ -728,7 +728,7 @@ func saveBlockchainVersion(db common.Database, bcVersion int) {
 
 // upgradeChainDatabase ensures that the chain database stores block split into
 // separate header and body entries.
-func upgradeChainDatabase(db common.Database) error {
+func upgradeChainDatabase(db ethdb.Database) error {
 	// Short circuit if the head block is stored already as separate header and body
 	data, err := db.Get([]byte("LastBlock"))
 	if err != nil {
diff --git a/eth/handler.go b/eth/handler.go
index 4aef69043..0a06ea335 100644
--- a/eth/handler.go
+++ b/eth/handler.go
@@ -28,6 +28,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/eth/downloader"
 	"github.com/ethereum/go-ethereum/eth/fetcher"
+	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
@@ -61,7 +62,7 @@ func (ep extProt) GetBlock(hashes []common.Hash) error { return ep.getBlocks(has
 type ProtocolManager struct {
 	txpool   txPool
 	chainman *core.ChainManager
-	chaindb  common.Database
+	chaindb  ethdb.Database
 
 	downloader *downloader.Downloader
 	fetcher    *fetcher.Fetcher
@@ -86,7 +87,7 @@ type ProtocolManager struct {
 
 // NewProtocolManager returns a new ethereum sub protocol manager. The Ethereum sub protocol manages peers capable
 // with the ethereum network.
-func NewProtocolManager(networkId int, mux *event.TypeMux, txpool txPool, pow pow.PoW, chainman *core.ChainManager, chaindb common.Database) *ProtocolManager {
+func NewProtocolManager(networkId int, mux *event.TypeMux, txpool txPool, pow pow.PoW, chainman *core.ChainManager, chaindb ethdb.Database) *ProtocolManager {
 	// Create the protocol manager with the base fields
 	manager := &ProtocolManager{
 		eventMux:  mux,
diff --git a/common/db.go b/ethdb/interface.go
similarity index 96%
rename from common/db.go
rename to ethdb/interface.go
index 60c090cdc..598e8eaa3 100644
--- a/common/db.go
+++ b/ethdb/interface.go
@@ -14,9 +14,8 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-package common
+package ethdb
 
-// Database interface
 type Database interface {
 	Put(key []byte, value []byte) error
 	Get(key []byte) ([]byte, error)
diff --git a/miner/agent.go b/miner/agent.go
index 7ccf8d2e0..e80b222c8 100644
--- a/miner/agent.go
+++ b/miner/agent.go
@@ -19,11 +19,12 @@ package miner
 import (
 	"sync"
 
+	"sync/atomic"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
 	"github.com/ethereum/go-ethereum/pow"
-	"sync/atomic"
 )
 
 type CpuAgent struct {
@@ -63,7 +64,7 @@ func (self *CpuAgent) Stop() {
 func (self *CpuAgent) Start() {
 	self.mu.Lock()
 	defer self.mu.Unlock()
-	
+
 	if !atomic.CompareAndSwapInt32(&self.isMining, 0, 1) {
 		return // agent already started
 	}
diff --git a/miner/worker.go b/miner/worker.go
index 2f43b110f..96c42c292 100644
--- a/miner/worker.go
+++ b/miner/worker.go
@@ -29,6 +29,7 @@ import (
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
@@ -100,7 +101,7 @@ type worker struct {
 	eth     core.Backend
 	chain   *core.ChainManager
 	proc    *core.BlockProcessor
-	chainDb common.Database
+	chainDb ethdb.Database
 
 	coinbase common.Address
 	gasPrice *big.Int
diff --git a/tests/block_test_util.go b/tests/block_test_util.go
index 30488951d..e31ca6344 100644
--- a/tests/block_test_util.go
+++ b/tests/block_test_util.go
@@ -197,7 +197,7 @@ func (test *BlockTest) makeEthConfig() *eth.Config {
 		Verbosity:      5,
 		Etherbase:      common.Address{},
 		AccountManager: accounts.NewManager(ks),
-		NewDB:          func(path string) (common.Database, error) { return ethdb.NewMemDatabase() },
+		NewDB:          func(path string) (ethdb.Database, error) { return ethdb.NewMemDatabase() },
 	}
 }
 
diff --git a/tests/util.go b/tests/util.go
index a9b5011a9..72d927ada 100644
--- a/tests/util.go
+++ b/tests/util.go
@@ -27,6 +27,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/ethdb"
 )
 
 func checkLogs(tlog []Log, logs state.Logs) error {
@@ -87,7 +88,7 @@ func (self Log) Topics() [][]byte {
 	return t
 }
 
-func StateObjectFromAccount(db common.Database, addr string, account Account) *state.StateObject {
+func StateObjectFromAccount(db ethdb.Database, addr string, account Account) *state.StateObject {
 	obj := state.NewStateObject(common.HexToAddress(addr), db)
 	obj.SetBalance(common.Big(account.Balance))
 

From 8b32f10f16f19c0b8985399fafdfe31af29493a1 Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@twurst.com>
Date: Tue, 18 Aug 2015 13:42:21 +0200
Subject: [PATCH 2/4] ethdb: add NewBatch

---
 ethdb/database.go        | 20 ++++++++++++++++++++
 ethdb/interface.go       |  6 ++++++
 ethdb/memory_database.go | 23 +++++++++++++++++++++++
 3 files changed, 49 insertions(+)

diff --git a/ethdb/database.go b/ethdb/database.go
index 9e80e5409..ad87f853d 100644
--- a/ethdb/database.go
+++ b/ethdb/database.go
@@ -268,3 +268,23 @@ func (self *LDBDatabase) meter(refresh time.Duration) {
 		}
 	}
 }
+
+// TODO: remove this stuff and expose leveldb directly
+
+func (db *LDBDatabase) NewBatch() Batch {
+	return &ldbBatch{db: db.db, b: new(leveldb.Batch)}
+}
+
+type ldbBatch struct {
+	db *leveldb.DB
+	b  *leveldb.Batch
+}
+
+func (b *ldbBatch) Put(key, value []byte) error {
+	b.b.Put(key, value)
+	return nil
+}
+
+func (b *ldbBatch) Write() error {
+	return b.db.Write(b.b, nil)
+}
diff --git a/ethdb/interface.go b/ethdb/interface.go
index 598e8eaa3..acb1b57c0 100644
--- a/ethdb/interface.go
+++ b/ethdb/interface.go
@@ -22,4 +22,10 @@ type Database interface {
 	Delete(key []byte) error
 	Close()
 	Flush() error
+	NewBatch() Batch
+}
+
+type Batch interface {
+	Put(key, value []byte) error
+	Write() error
 }
diff --git a/ethdb/memory_database.go b/ethdb/memory_database.go
index d50f8f9d4..4fcce1812 100644
--- a/ethdb/memory_database.go
+++ b/ethdb/memory_database.go
@@ -95,3 +95,26 @@ func (db *MemDatabase) LastKnownTD() []byte {
 func (db *MemDatabase) Flush() error {
 	return nil
 }
+
+func (db *MemDatabase) NewBatch() Batch {
+	return &memBatch{db: db}
+}
+
+type kv struct{ k, v []byte }
+
+type memBatch struct {
+	db     *MemDatabase
+	writes []kv
+}
+
+func (w *memBatch) Put(key, value []byte) error {
+	w.writes = append(w.writes, kv{key, common.CopyBytes(value)})
+	return nil
+}
+
+func (w *memBatch) Write() error {
+	for _, kv := range w.writes {
+		w.db.db[string(kv.k)] = kv.v
+	}
+	return nil
+}

From d581dfee5fbd46f3e6c54e3fab2717105e6bd510 Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@twurst.com>
Date: Mon, 6 Jul 2015 01:19:16 +0200
Subject: [PATCH 3/4] ethdb: copy stored memdb values

Storing a value in LevelDB copies the bytes, modifying the value
afterwards does not affect the content of the database. This commit
ensures that MemDatabase satisfies the same property.
---
 ethdb/memory_database.go | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/ethdb/memory_database.go b/ethdb/memory_database.go
index 4fcce1812..fd5663fec 100644
--- a/ethdb/memory_database.go
+++ b/ethdb/memory_database.go
@@ -36,8 +36,7 @@ func NewMemDatabase() (*MemDatabase, error) {
 }
 
 func (db *MemDatabase) Put(key []byte, value []byte) error {
-	db.db[string(key)] = value
-
+	db.db[string(key)] = common.CopyBytes(value)
 	return nil
 }
 

From b25258996059439df82687cc653ed14a5a9edce1 Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@twurst.com>
Date: Mon, 14 Sep 2015 09:45:40 +0200
Subject: [PATCH 4/4] ethdb: remove Flush

---
 eth/backend.go           | 35 ++---------------------------------
 ethdb/database.go        | 21 ++++++++-------------
 ethdb/interface.go       |  1 -
 ethdb/memory_database.go |  4 ----
 4 files changed, 10 insertions(+), 51 deletions(-)

diff --git a/eth/backend.go b/eth/backend.go
index a923cfa78..349dfa613 100644
--- a/eth/backend.go
+++ b/eth/backend.go
@@ -213,9 +213,6 @@ type Ethereum struct {
 	chainDb ethdb.Database // Block chain database
 	dappDb  ethdb.Database // Dapp database
 
-	// Closed when databases are flushed and closed
-	databasesClosed chan bool
-
 	//*** SERVICES ***
 	// State manager for processing new blocks and managing the over all states
 	blockProcessor  *core.BlockProcessor
@@ -337,7 +334,6 @@ func New(config *Config) (*Ethereum, error) {
 
 	eth := &Ethereum{
 		shutdownChan:            make(chan bool),
-		databasesClosed:         make(chan bool),
 		chainDb:                 chainDb,
 		dappDb:                  dappDb,
 		eventMux:                &event.TypeMux{},
@@ -549,8 +545,6 @@ func (s *Ethereum) Start() error {
 	if err != nil {
 		return err
 	}
-	// periodically flush databases
-	go s.syncDatabases()
 
 	if s.AutoDAG {
 		s.StartAutoDAG()
@@ -566,32 +560,6 @@ func (s *Ethereum) Start() error {
 	return nil
 }
 
-// sync databases every minute. If flushing fails we exit immediatly. The system
-// may not continue under any circumstances.
-func (s *Ethereum) syncDatabases() {
-	ticker := time.NewTicker(1 * time.Minute)
-done:
-	for {
-		select {
-		case <-ticker.C:
-			// don't change the order of database flushes
-			if err := s.dappDb.Flush(); err != nil {
-				glog.Fatalf("fatal error: flush dappDb: %v (Restart your node. We are aware of this issue)\n", err)
-			}
-			if err := s.chainDb.Flush(); err != nil {
-				glog.Fatalf("fatal error: flush chainDb: %v (Restart your node. We are aware of this issue)\n", err)
-			}
-		case <-s.shutdownChan:
-			break done
-		}
-	}
-
-	s.chainDb.Close()
-	s.dappDb.Close()
-
-	close(s.databasesClosed)
-}
-
 func (s *Ethereum) StartForTest() {
 	jsonlogger.LogJson(&logger.LogStarting{
 		ClientString:    s.net.Name,
@@ -622,12 +590,13 @@ func (s *Ethereum) Stop() {
 	}
 	s.StopAutoDAG()
 
+	s.chainDb.Close()
+	s.dappDb.Close()
 	close(s.shutdownChan)
 }
 
 // This function will wait for a shutdown and resumes main thread execution
 func (s *Ethereum) WaitForShutdown() {
-	<-s.databasesClosed
 	<-s.shutdownChan
 }
 
diff --git a/ethdb/database.go b/ethdb/database.go
index ad87f853d..047821c30 100644
--- a/ethdb/database.go
+++ b/ethdb/database.go
@@ -61,9 +61,7 @@ type LDBDatabase struct {
 	quitChan chan chan error // Quit channel to stop the metrics collection before closing the database
 }
 
-// NewLDBDatabase returns a LevelDB wrapped object. LDBDatabase does not persist data by
-// it self but requires a background poller which syncs every X. `Flush` should be called
-// when data needs to be stored and written to disk.
+// NewLDBDatabase returns a LevelDB wrapped object.
 func NewLDBDatabase(file string, cache int) (*LDBDatabase, error) {
 	// Calculate the cache allowance for this particular database
 	cache = int(float64(cache) * cacheRatio[filepath.Base(file)])
@@ -142,11 +140,6 @@ func (self *LDBDatabase) NewIterator() iterator.Iterator {
 	return self.db.NewIterator(nil, nil)
 }
 
-// Flush flushes out the queue to leveldb
-func (self *LDBDatabase) Flush() error {
-	return nil
-}
-
 func (self *LDBDatabase) Close() {
 	// Stop the metrics collection to avoid internal database races
 	self.quitLock.Lock()
@@ -159,12 +152,14 @@ func (self *LDBDatabase) Close() {
 			glog.V(logger.Error).Infof("metrics failure in '%s': %v\n", self.fn, err)
 		}
 	}
-	// Flush and close the database
-	if err := self.Flush(); err != nil {
-		glog.V(logger.Error).Infof("flushing '%s' failed: %v\n", self.fn, err)
+	err := self.db.Close()
+	if glog.V(logger.Error) {
+		if err == nil {
+			glog.Infoln("closed db:", self.fn)
+		} else {
+			glog.Errorf("error closing db %s: %v", self.fn, err)
+		}
 	}
-	self.db.Close()
-	glog.V(logger.Error).Infoln("flushed and closed db:", self.fn)
 }
 
 func (self *LDBDatabase) LDB() *leveldb.DB {
diff --git a/ethdb/interface.go b/ethdb/interface.go
index acb1b57c0..f4b787a52 100644
--- a/ethdb/interface.go
+++ b/ethdb/interface.go
@@ -21,7 +21,6 @@ type Database interface {
 	Get(key []byte) ([]byte, error)
 	Delete(key []byte) error
 	Close()
-	Flush() error
 	NewBatch() Batch
 }
 
diff --git a/ethdb/memory_database.go b/ethdb/memory_database.go
index fd5663fec..81911f23f 100644
--- a/ethdb/memory_database.go
+++ b/ethdb/memory_database.go
@@ -91,10 +91,6 @@ func (db *MemDatabase) LastKnownTD() []byte {
 	return data
 }
 
-func (db *MemDatabase) Flush() error {
-	return nil
-}
-
 func (db *MemDatabase) NewBatch() Batch {
 	return &memBatch{db: db}
 }