post-genesis transition (#426)

Support post-genesis transition

Reactivate a post-genesis transition for a kaustinen-like testnet that goes through the conversion.

It adds the ability:

 * To undergo the verkle transition "verge" past the genesis block, which so far was impossible with kaustinen-with-shapella.
 * To perform a shadow fork of holesky in the special kurtosis setup defined by the devops team.

It is also serving as the basis for multiple other branches, to be merged at a later time:

 * The branch to replay historical blocks in verkle 
 * The branch to execute transition tests

Co-authored-by: Ignacio Hagopian <jsign.uy@gmail.com>

cmd/geth/config.go

@@ -175,6 +175,17 @@ func makeFullNode(ctx *cli.Context) (*node.Node, ethapi.Backend) {
 		v := ctx.Uint64(utils.OverridePrague.Name)
 		cfg.Eth.OverridePrague = &v
 	}
+	if ctx.IsSet(utils.OverrideProofInBlock.Name) {
+		v := ctx.Bool(utils.OverrideProofInBlock.Name)
+		cfg.Eth.OverrideProofInBlock = &v
+	}
+	if ctx.IsSet(utils.OverrideOverlayStride.Name) {
+		v := ctx.Uint64(utils.OverrideOverlayStride.Name)
+		cfg.Eth.OverrideOverlayStride = &v
+	}
+	if ctx.IsSet(utils.ClearVerkleCosts.Name) {
+		params.ClearVerkleWitnessCosts()
+	}
 	backend, eth := utils.RegisterEthService(stack, &cfg.Eth)
 
 	// Configure log filter RPC API.

cmd/geth/main.go

@@ -67,8 +67,11 @@ var (
 		utils.NoUSBFlag,
 		utils.USBFlag,
 		utils.SmartCardDaemonPathFlag,
+		utils.OverrideOverlayStride,
 		utils.OverrideCancun,
 		utils.OverridePrague,
+		utils.OverrideProofInBlock,
+		utils.ClearVerkleCosts,
 		utils.EnablePersonal,
 		utils.TxPoolLocalsFlag,
 		utils.TxPoolNoLocalsFlag,

cmd/utils/flags.go

@@ -263,6 +263,12 @@ var (
 		Value:    2048,
 		Category: flags.EthCategory,
 	}
+	OverrideOverlayStride = &cli.Uint64Flag{
+		Name:     "override.overlay-stride",
+		Usage:    "Manually specify the stride of the overlay transition, overriding the bundled setting",
+		Value:    10000,
+		Category: flags.EthCategory,
+	}
 	OverrideCancun = &cli.Uint64Flag{
 		Name:     "override.cancun",
 		Usage:    "Manually specify the Cancun fork timestamp, overriding the bundled setting",
@@ -273,6 +279,17 @@ var (
 		Usage:    "Manually specify the Verkle fork timestamp, overriding the bundled setting",
 		Category: flags.EthCategory,
 	}
+	OverrideProofInBlock = &cli.BoolFlag{
+		Name:     "override.blockproof",
+		Usage:    "Manually specify the proof-in-block setting",
+		Value:    true,
+		Category: flags.EthCategory,
+	}
+	ClearVerkleCosts = &cli.BoolFlag{
+		Name:     "clear.verkle.costs",
+		Usage:    "Clear verkle costs (for shadow forks)",
+		Category: flags.EthCategory,
+	}
 	// Light server and client settings
 	LightServeFlag = &cli.IntFlag{
 		Name:     "light.serve",

consensus/beacon/consensus.go

@@ -25,8 +25,10 @@ import (
 	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/consensus/misc/eip1559"
 	"github.com/ethereum/go-ethereum/consensus/misc/eip4844"
+	"github.com/ethereum/go-ethereum/core/overlay"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rpc"
 	"github.com/ethereum/go-ethereum/trie"
@@ -358,6 +360,15 @@ func (beacon *Beacon) Finalize(chain consensus.ChainHeaderReader, header *types.
 		// The returned gas is not charged
 		state.Witness().TouchFullAccount(w.Address[:], true)
 	}
+
+	if chain.Config().IsPrague(header.Number, header.Time) {
+		// uncomment when debugging
+		// fmt.Println("at block", header.Number, "performing transition?", state.Database().InTransition())
+		parent := chain.GetHeaderByHash(header.ParentHash)
+		if err := overlay.OverlayVerkleTransition(state, parent.Root, chain.Config().OverlayStride); err != nil {
+			log.Error("error performing the transition", "err", err)
+		}
+	}
 }
 
 // FinalizeAndAssemble implements consensus.Engine, setting the final state and
@@ -382,19 +393,27 @@ func (beacon *Beacon) FinalizeAndAssemble(chain consensus.ChainHeaderReader, hea
 
 	// Assign the final state root to header.
 	header.Root = state.IntermediateRoot(true)
+	// Associate current conversion state to computed state
+	// root and store it in the database for later recovery.
+	state.Database().SaveTransitionState(header.Root)
 
 	var (
 		p    *verkle.VerkleProof
 		k    verkle.StateDiff
 		keys = state.Witness().Keys()
 	)
-	if chain.Config().IsPrague(header.Number, header.Time) && chain.Config().ProofInBlocks {
+	if chain.Config().IsPrague(header.Number, header.Time) {
 		// Open the pre-tree to prove the pre-state against
 		parent := chain.GetHeaderByNumber(header.Number.Uint64() - 1)
 		if parent == nil {
 			return nil, fmt.Errorf("nil parent header for block %d", header.Number)
 		}
 
+		// Load transition state at beginning of block, because
+		// OpenTrie needs to know what the conversion status is.
+		state.Database().LoadTransitionState(parent.Root)
+
+		if chain.Config().ProofInBlocks {
 			preTrie, err := state.Database().OpenTrie(parent.Root)
 			if err != nil {
 				return nil, fmt.Errorf("error opening pre-state tree root: %w", err)
@@ -405,7 +424,19 @@ func (beacon *Beacon) FinalizeAndAssemble(chain consensus.ChainHeaderReader, hea
 			switch pre := preTrie.(type) {
 			case *trie.VerkleTrie:
 				vtrpre, okpre = preTrie.(*trie.VerkleTrie)
-			vtrpost, okpost = state.GetTrie().(*trie.VerkleTrie)
+				switch tr := state.GetTrie().(type) {
+				case *trie.VerkleTrie:
+					vtrpost = tr
+					okpost = true
+				// This is to handle a situation right at the start of the conversion:
+				// the post trie is a transition tree when the pre tree is an empty
+				// verkle tree.
+				case *trie.TransitionTrie:
+					vtrpost = tr.Overlay()
+					okpost = true
+				default:
+					okpost = false
+				}
 			case *trie.TransitionTrie:
 				vtrpre = pre.Overlay()
 				okpre = true
@@ -431,6 +462,7 @@ func (beacon *Beacon) FinalizeAndAssemble(chain consensus.ChainHeaderReader, hea
 				}
 			}
 		}
+	}
 
 	// Assemble and return the final block.
 	block := types.NewBlockWithWithdrawals(header, txs, uncles, receipts, withdrawals, trie.NewStackTrie(nil))

core/block_validator.go

@@ -131,6 +131,10 @@ func (v *BlockValidator) ValidateState(block *types.Block, statedb *state.StateD
 	if root := statedb.IntermediateRoot(v.config.IsEIP158(header.Number)); header.Root != root {
 		return fmt.Errorf("invalid merkle root (remote: %x local: %x) dberr: %w", header.Root, root, statedb.Error())
 	}
+	// Verify that the advertised root is correct before
+	// it can be used as an identifier for the conversion
+	// status.
+	statedb.Database().SaveTransitionState(header.Root)
 	return nil
 }
 

core/blockchain.go

@@ -251,6 +251,14 @@ func NewBlockChain(db ethdb.Database, cacheConfig *CacheConfig, genesis *Genesis
 	if _, ok := genesisErr.(*params.ConfigCompatError); genesisErr != nil && !ok {
 		return nil, genesisErr
 	}
+	if overrides != nil {
+		if overrides.OverrideProofInBlock != nil {
+			chainConfig.ProofInBlocks = *overrides.OverrideProofInBlock
+		}
+		if overrides.OverrideOverlayStride != nil {
+			chainConfig.OverlayStride = *overrides.OverrideOverlayStride
+		}
+	}
 	log.Info("")
 	log.Info(strings.Repeat("-", 153))
 	for _, line := range strings.Split(chainConfig.Description(), "\n") {
@@ -312,7 +320,13 @@ func NewBlockChain(db ethdb.Database, cacheConfig *CacheConfig, genesis *Genesis
 	head := bc.CurrentBlock()
 
 	// Declare the end of the verkle transition if need be
-	if bc.chainConfig.Rules(head.Number, false /* XXX */, head.Time).IsPrague {
+	if bc.chainConfig.IsPrague(head.Number, head.Time) {
+		// TODO this only works when resuming a chain that has already gone
+		// through the conversion. All pointers should be saved to the DB
+		// for it to be able to recover if interrupted during the transition
+		// but that's left out to a later PR since there's not really a need
+		// right now.
+		bc.stateCache.InitTransitionStatus(true, true)
 		bc.stateCache.EndVerkleTransition()
 	}
 
@@ -1746,8 +1760,22 @@ func (bc *BlockChain) insertChain(chain types.Blocks, setHead bool) (int, error)
 			parent = bc.GetHeader(block.ParentHash(), block.NumberU64()-1)
 		}
 
+		if bc.Config().IsPrague(block.Number(), block.Time()) {
+			bc.stateCache.LoadTransitionState(parent.Root)
+
+			// pragueTime has been reached. If the transition isn't active, it means this
+			// is the fork block and that the conversion needs to be marked at started.
+			if !bc.stateCache.InTransition() && !bc.stateCache.Transitioned() {
+				bc.stateCache.StartVerkleTransition(parent.Root, emptyVerkleRoot, bc.Config(), bc.Config().PragueTime, parent.Root)
+			}
+		} else {
+			// If the verkle activation time hasn't started, declare it as "not started".
+			// This is so that if the miner activates the conversion, the insertion happens
+			// in the correct mode.
+			bc.stateCache.InitTransitionStatus(false, false)
+		}
 		if parent.Number.Uint64() == conversionBlock {
-			bc.StartVerkleTransition(parent.Root, emptyVerkleRoot, bc.Config(), &parent.Time)
+			bc.StartVerkleTransition(parent.Root, emptyVerkleRoot, bc.Config(), &parent.Time, parent.Root)
 			bc.stateCache.SetLastMerkleRoot(parent.Root)
 		}
 		statedb, err := state.New(parent.Root, bc.stateCache, bc.snaps)
@@ -1989,7 +2017,7 @@ func (bc *BlockChain) insertSideChain(block *types.Block, it *insertIterator) (i
 		parent = bc.GetHeader(parent.ParentHash, parent.Number.Uint64()-1)
 	}
 	if parent == nil {
-		return it.index, errors.New("missing parent")
+		return it.index, fmt.Errorf("missing parent: hash=%x, number=%d", current.Hash(), current.Number)
 	}
 	// Import all the pruned blocks to make the state available
 	var (
@@ -2050,7 +2078,7 @@ func (bc *BlockChain) recoverAncestors(block *types.Block) (common.Hash, error)
 		}
 	}
 	if parent == nil {
-		return common.Hash{}, errors.New("missing parent")
+		return common.Hash{}, fmt.Errorf("missing parent during ancestor recovery: hash=%x, number=%d", block.ParentHash(), block.Number())
 	}
 	// Import all the pruned blocks to make the state available
 	for i := len(hashes) - 1; i >= 0; i-- {
@@ -2288,6 +2316,7 @@ func (bc *BlockChain) SetCanonical(head *types.Block) (common.Hash, error) {
 	defer bc.chainmu.Unlock()
 
 	// Re-execute the reorged chain in case the head state is missing.
+	log.Trace("looking for state", "root", head.Root(), "has state", bc.HasState(head.Root()))
 	if !bc.HasState(head.Root()) {
 		if latestValidHash, err := bc.recoverAncestors(head); err != nil {
 			return latestValidHash, err
@@ -2533,8 +2562,8 @@ func (bc *BlockChain) GetTrieFlushInterval() time.Duration {
 	return time.Duration(bc.flushInterval.Load())
 }
 
-func (bc *BlockChain) StartVerkleTransition(originalRoot, translatedRoot common.Hash, chainConfig *params.ChainConfig, pragueTime *uint64) {
+func (bc *BlockChain) StartVerkleTransition(originalRoot, translatedRoot common.Hash, chainConfig *params.ChainConfig, pragueTime *uint64, root common.Hash) {
-	bc.stateCache.StartVerkleTransition(originalRoot, translatedRoot, chainConfig, pragueTime)
+	bc.stateCache.StartVerkleTransition(originalRoot, translatedRoot, chainConfig, pragueTime, root)
 }
 func (bc *BlockChain) ReorgThroughVerkleTransition() {
 	bc.stateCache.ReorgThroughVerkleTransition()

core/chain_makers.go

@@ -365,7 +365,7 @@ func GenerateChainWithGenesis(genesis *Genesis, engine consensus.Engine, n int,
 	return db, blocks, receipts
 }
 
-func GenerateVerkleChain(config *params.ChainConfig, parent *types.Block, engine consensus.Engine, db ethdb.Database, n int, gen func(int, *BlockGen)) ([]*types.Block, []types.Receipts, []*verkle.VerkleProof, []verkle.StateDiff) {
+func GenerateVerkleChain(config *params.ChainConfig, parent *types.Block, engine consensus.Engine, diskdb ethdb.Database, n int, gen func(int, *BlockGen)) ([]*types.Block, []types.Receipts, []*verkle.VerkleProof, []verkle.StateDiff) {
 	if config == nil {
 		config = params.TestChainConfig
 	}
@@ -434,13 +434,16 @@ func GenerateVerkleChain(config *params.ChainConfig, parent *types.Block, engine
 		return nil, nil
 	}
 	var snaps *snapshot.Tree
-	triedb := state.NewDatabaseWithConfig(db, nil)
+	db := state.NewDatabaseWithConfig(diskdb, nil)
-	triedb.EndVerkleTransition()
+	db.StartVerkleTransition(common.Hash{}, common.Hash{}, config, config.PragueTime, common.Hash{})
+	db.EndVerkleTransition()
+	db.SaveTransitionState(parent.Root())
 	for i := 0; i < n; i++ {
-		statedb, err := state.New(parent.Root(), triedb, snaps)
+		statedb, err := state.New(parent.Root(), db, snaps)
 		if err != nil {
 			panic(fmt.Sprintf("could not find state for block %d: err=%v, parent root=%x", i, err, parent.Root()))
 		}
+		statedb.NewAccessWitness()
 		block, receipt := genblock(i, parent, statedb)
 		blocks[i] = block
 		receipts[i] = receipt

core/genesis.go

@@ -126,6 +126,7 @@ func (ga *GenesisAlloc) deriveHash(cfg *params.ChainConfig, timestamp uint64) (c
 	// all the derived states will be discarded to not pollute disk.
 	db := state.NewDatabase(rawdb.NewMemoryDatabase())
 	if cfg.IsPrague(big.NewInt(int64(0)), timestamp) {
+		db.StartVerkleTransition(common.Hash{}, common.Hash{}, cfg, &timestamp, common.Hash{})
 		db.EndVerkleTransition()
 	}
 	statedb, err := state.New(types.EmptyRootHash, db, nil)
@@ -146,15 +147,17 @@ func (ga *GenesisAlloc) deriveHash(cfg *params.ChainConfig, timestamp uint64) (c
 // flush is very similar with deriveHash, but the main difference is
 // all the generated states will be persisted into the given database.
 // Also, the genesis state specification will be flushed as well.
-func (ga *GenesisAlloc) flush(db ethdb.Database, triedb *trie.Database, blockhash common.Hash, cfg *params.ChainConfig) error {
+func (ga *GenesisAlloc) flush(db ethdb.Database, triedb *trie.Database, blockhash common.Hash, cfg *params.ChainConfig, timestamp *uint64) error {
-	statedb, err := state.New(types.EmptyRootHash, state.NewDatabaseWithNodeDB(db, triedb), nil)
+	database := state.NewDatabaseWithNodeDB(db, triedb)
-	if err != nil {
+	// End the verkle conversion at genesis if the fork block is 0
-		return err
+	if timestamp != nil && cfg.IsPrague(big.NewInt(int64(0)), *timestamp) {
+		database.StartVerkleTransition(common.Hash{}, common.Hash{}, cfg, timestamp, common.Hash{})
+		database.EndVerkleTransition()
 	}
 
-	// End the verkle conversion at genesis if the fork block is 0
+	statedb, err := state.New(types.EmptyRootHash, database, nil)
-	if triedb.IsVerkle() {
+	if err != nil {
-		statedb.Database().EndVerkleTransition()
+		return err
 	}
 
 	for addr, account := range *ga {
@@ -221,7 +224,7 @@ func CommitGenesisState(db ethdb.Database, triedb *trie.Database, blockhash comm
 			return errors.New("not found")
 		}
 	}
-	return alloc.flush(db, triedb, blockhash, config)
+	return alloc.flush(db, triedb, blockhash, config, nil)
 }
 
 // GenesisAccount is an account in the state of the genesis block.
@@ -290,6 +293,8 @@ func (e *GenesisMismatchError) Error() string {
 type ChainOverrides struct {
 	OverrideCancun        *uint64
 	OverridePrague        *uint64
+	OverrideProofInBlock  *bool
+	OverrideOverlayStride *uint64
 }
 
 // SetupGenesisBlock writes or updates the genesis block in db.
@@ -536,7 +541,7 @@ func (g *Genesis) Commit(db ethdb.Database, triedb *trie.Database) (*types.Block
 	// All the checks has passed, flush the states derived from the genesis
 	// specification as well as the specification itself into the provided
 	// database.
-	if err := g.Alloc.flush(db, triedb, block.Hash(), g.Config); err != nil {
+	if err := g.Alloc.flush(db, triedb, block.Hash(), g.Config, &g.Timestamp); err != nil {
 		return nil, err
 	}
 	rawdb.WriteTd(db, block.Hash(), block.NumberU64(), block.Difficulty())

core/overlay/conversion.go

@@ -14,14 +14,17 @@
 // 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 core
+package overlay
 
 import (
 	"bufio"
 	"bytes"
+	"encoding/binary"
 	"fmt"
 	"io"
 	"os"
+	"runtime"
+	"sync"
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -32,15 +35,199 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/trie"
+	"github.com/ethereum/go-ethereum/trie/utils"
+	"github.com/ethereum/go-verkle"
+	"github.com/holiman/uint256"
 )
 
+var zeroTreeIndex uint256.Int
+
+// keyValueMigrator is a helper module that collects key-values from the overlay-tree migration for Verkle Trees.
+// It assumes that the walk of the base tree is done in address-order, so it exploit that fact to
+// collect the key-values in a way that is efficient.
+type keyValueMigrator struct {
+	// leafData contains the values for the future leaf for a particular VKT branch.
+	leafData map[branchKey]*migratedKeyValue
+
+	// When prepare() is called, it will start a background routine that will process the leafData
+	// saving the result in newLeaves to be used by migrateCollectedKeyValues(). The background
+	// routine signals that it is done by closing processingReady.
+	processingReady chan struct{}
+	newLeaves       []verkle.LeafNode
+	prepareErr      error
+}
+
+func newKeyValueMigrator() *keyValueMigrator {
+	// We do initialize the VKT config since prepare() might indirectly make multiple GetConfig() calls
+	// in different goroutines when we never called GetConfig() before, causing a race considering the way
+	// that `config` is designed in go-verkle.
+	// TODO: jsign as a fix for this in the PR where we move to a file-less precomp, since it allows safe
+	//       concurrent calls to GetConfig(). When that gets merged, we can remove this line.
+	_ = verkle.GetConfig()
+	return &keyValueMigrator{
+		processingReady: make(chan struct{}),
+		leafData:        make(map[branchKey]*migratedKeyValue, 10_000),
+	}
+}
+
+type migratedKeyValue struct {
+	branchKey    branchKey
+	leafNodeData verkle.BatchNewLeafNodeData
+}
+type branchKey struct {
+	addr      common.Address
+	treeIndex uint256.Int
+}
+
+func newBranchKey(addr []byte, treeIndex *uint256.Int) branchKey {
+	var sk branchKey
+	copy(sk.addr[:], addr)
+	sk.treeIndex = *treeIndex
+	return sk
+}
+
+func (kvm *keyValueMigrator) addStorageSlot(addr []byte, slotNumber []byte, slotValue []byte) {
+	treeIndex, subIndex := utils.GetTreeKeyStorageSlotTreeIndexes(slotNumber)
+	leafNodeData := kvm.getOrInitLeafNodeData(newBranchKey(addr, treeIndex))
+	leafNodeData.Values[subIndex] = slotValue
+}
+
+func (kvm *keyValueMigrator) addAccount(addr []byte, acc *types.StateAccount) {
+	leafNodeData := kvm.getOrInitLeafNodeData(newBranchKey(addr, &zeroTreeIndex))
+
+	var version [verkle.LeafValueSize]byte
+	leafNodeData.Values[utils.VersionLeafKey] = version[:]
+
+	var balance [verkle.LeafValueSize]byte
+	for i, b := range acc.Balance.Bytes() {
+		balance[len(acc.Balance.Bytes())-1-i] = b
+	}
+	leafNodeData.Values[utils.BalanceLeafKey] = balance[:]
+
+	var nonce [verkle.LeafValueSize]byte
+	binary.LittleEndian.PutUint64(nonce[:8], acc.Nonce)
+	leafNodeData.Values[utils.NonceLeafKey] = nonce[:]
+
+	leafNodeData.Values[utils.CodeHashLeafKey] = acc.CodeHash[:]
+}
+
+func (kvm *keyValueMigrator) addAccountCode(addr []byte, codeSize uint64, chunks []byte) {
+	leafNodeData := kvm.getOrInitLeafNodeData(newBranchKey(addr, &zeroTreeIndex))
+
+	// Save the code size.
+	var codeSizeBytes [verkle.LeafValueSize]byte
+	binary.LittleEndian.PutUint64(codeSizeBytes[:8], codeSize)
+	leafNodeData.Values[utils.CodeSizeLeafKey] = codeSizeBytes[:]
+
+	// The first 128 chunks are stored in the account header leaf.
+	for i := 0; i < 128 && i < len(chunks)/32; i++ {
+		leafNodeData.Values[byte(128+i)] = chunks[32*i : 32*(i+1)]
+	}
+
+	// Potential further chunks, have their own leaf nodes.
+	for i := 128; i < len(chunks)/32; {
+		treeIndex, _ := utils.GetTreeKeyCodeChunkIndices(uint256.NewInt(uint64(i)))
+		leafNodeData := kvm.getOrInitLeafNodeData(newBranchKey(addr, treeIndex))
+
+		j := i
+		for ; (j-i) < 256 && j < len(chunks)/32; j++ {
+			leafNodeData.Values[byte((j-128)%256)] = chunks[32*j : 32*(j+1)]
+		}
+		i = j
+	}
+}
+
+func (kvm *keyValueMigrator) getOrInitLeafNodeData(bk branchKey) *verkle.BatchNewLeafNodeData {
+	if ld, ok := kvm.leafData[bk]; ok {
+		return &ld.leafNodeData
+	}
+	kvm.leafData[bk] = &migratedKeyValue{
+		branchKey: bk,
+		leafNodeData: verkle.BatchNewLeafNodeData{
+			Stem:   nil, // It will be calculated in the prepare() phase, since it's CPU heavy.
+			Values: make(map[byte][]byte, 256),
+		},
+	}
+	return &kvm.leafData[bk].leafNodeData
+}
+
+func (kvm *keyValueMigrator) prepare() {
+	// We fire a background routine to process the leafData and save the result in newLeaves.
+	// The background routine signals that it is done by closing processingReady.
+	go func() {
+		// Step 1: We split kvm.leafData in numBatches batches, and we process each batch in a separate goroutine.
+		//         This fills each leafNodeData.Stem with the correct value.
+		leafData := make([]migratedKeyValue, 0, len(kvm.leafData))
+		for _, v := range kvm.leafData {
+			leafData = append(leafData, *v)
+		}
+		var wg sync.WaitGroup
+		batchNum := runtime.NumCPU()
+		batchSize := (len(kvm.leafData) + batchNum - 1) / batchNum
+		for i := 0; i < len(kvm.leafData); i += batchSize {
+			start := i
+			end := i + batchSize
+			if end > len(kvm.leafData) {
+				end = len(kvm.leafData)
+			}
+			wg.Add(1)
+
+			batch := leafData[start:end]
+			go func() {
+				defer wg.Done()
+				var currAddr common.Address
+				var currPoint *verkle.Point
+				for i := range batch {
+					if batch[i].branchKey.addr != currAddr || currAddr == (common.Address{}) {
+						currAddr = batch[i].branchKey.addr
+						currPoint = utils.EvaluateAddressPoint(currAddr[:])
+					}
+					stem := utils.GetTreeKeyWithEvaluatedAddess(currPoint, &batch[i].branchKey.treeIndex, 0)
+					stem = stem[:verkle.StemSize]
+					batch[i].leafNodeData.Stem = stem
+				}
+			}()
+		}
+		wg.Wait()
+
+		// Step 2: Now that we have all stems (i.e: tree keys) calculated, we can create the new leaves.
+		nodeValues := make([]verkle.BatchNewLeafNodeData, len(kvm.leafData))
+		for i := range leafData {
+			nodeValues[i] = leafData[i].leafNodeData
+		}
+
+		// Create all leaves in batch mode so we can optimize cryptography operations.
+		kvm.newLeaves, kvm.prepareErr = verkle.BatchNewLeafNode(nodeValues)
+		close(kvm.processingReady)
+	}()
+}
+
+func (kvm *keyValueMigrator) migrateCollectedKeyValues(tree *trie.VerkleTrie) error {
+	now := time.Now()
+	<-kvm.processingReady
+	if kvm.prepareErr != nil {
+		return fmt.Errorf("failed to prepare key values: %w", kvm.prepareErr)
+	}
+	log.Info("Prepared key values from base tree", "duration", time.Since(now))
+
+	// Insert into the tree.
+	if err := tree.InsertMigratedLeaves(kvm.newLeaves); err != nil {
+		return fmt.Errorf("failed to insert migrated leaves: %w", err)
+	}
+
+	return nil
+}
+
 // OverlayVerkleTransition contains the overlay conversion logic
-func OverlayVerkleTransition(statedb *state.StateDB) error {
+func OverlayVerkleTransition(statedb *state.StateDB, root common.Hash, maxMovedCount uint64) error {
 	migrdb := statedb.Database()
+	migrdb.LockCurrentTransitionState()
+	defer migrdb.UnLockCurrentTransitionState()
 
 	// verkle transition: if the conversion process is in progress, move
 	// N values from the MPT into the verkle tree.
 	if migrdb.InTransition() {
+		log.Debug("Processing verkle conversion starting", "account hash", migrdb.GetCurrentAccountHash(), "slot hash", migrdb.GetCurrentSlotHash(), "state root", root)
 		var (
 			now             = time.Now()
 			tt              = statedb.GetTrie().(*trie.TransitionTrie)
@@ -92,14 +279,13 @@ func OverlayVerkleTransition(statedb *state.StateDB) error {
 			preimageSeek += int64(len(addr))
 		}
 
-		const maxMovedCount = 10000
 		// mkv will be assiting in the collection of up to maxMovedCount key values to be migrated to the VKT.
 		// It has internal caches to do efficient MPT->VKT key calculations, which will be discarded after
 		// this function.
 		mkv := newKeyValueMigrator()
 		// move maxCount accounts into the verkle tree, starting with the
 		// slots from the previous account.
-		count := 0
+		count := uint64(0)
 
 		// if less than maxCount slots were moved, move to the next account
 		for count < maxMovedCount {
@@ -124,7 +310,12 @@ func OverlayVerkleTransition(statedb *state.StateDB) error {
 				if err != nil {
 					return err
 				}
-				stIt.Next()
+				processed := stIt.Next()
+				if processed {
+					log.Debug("account has storage and a next item")
+				} else {
+					log.Debug("account has storage and NO next item")
+				}
 
 				// fdb.StorageProcessed will be initialized to `true` if the
 				// entire storage for an account was not entirely processed
@@ -133,6 +324,7 @@ func OverlayVerkleTransition(statedb *state.StateDB) error {
 				// If the entire storage was processed, then the iterator was
 				// created in vain, but it's ok as this will not happen often.
 				for ; !migrdb.GetStorageProcessed() && count < maxMovedCount; count++ {
+					log.Trace("Processing storage", "count", count, "slot", stIt.Slot(), "storage processed", migrdb.GetStorageProcessed(), "current account", migrdb.GetCurrentAccountAddress(), "current account hash", migrdb.GetCurrentAccountHash())
 					var (
 						value     []byte   // slot value after RLP decoding
 						safeValue [32]byte // 32-byte aligned value
@@ -155,6 +347,7 @@ func OverlayVerkleTransition(statedb *state.StateDB) error {
 							return fmt.Errorf("slotnr len is zero is not 32: %d", len(slotnr))
 						}
 					}
+					log.Trace("found slot number", "number", slotnr)
 					if crypto.Keccak256Hash(slotnr[:]) != stIt.Hash() {
 						return fmt.Errorf("preimage file does not match storage hash: %s!=%s", crypto.Keccak256Hash(slotnr), stIt.Hash())
 					}
@@ -196,6 +389,7 @@ func OverlayVerkleTransition(statedb *state.StateDB) error {
 				// Move to the next account, if available - or end
 				// the transition otherwise.
 				if accIt.Next() {
+					log.Trace("Found another account to convert", "hash", accIt.Hash())
 					var addr common.Address
 					if hasPreimagesBin {
 						if _, err := io.ReadFull(fpreimages, addr[:]); err != nil {
@@ -207,10 +401,10 @@ func OverlayVerkleTransition(statedb *state.StateDB) error {
 							return fmt.Errorf("account address len is zero is not 20: %d", len(addr))
 						}
 					}
-					// fmt.Printf("account switch: %s != %s\n", crypto.Keccak256Hash(addr[:]), accIt.Hash())
 					if crypto.Keccak256Hash(addr[:]) != accIt.Hash() {
 						return fmt.Errorf("preimage file does not match account hash: %s != %s", crypto.Keccak256Hash(addr[:]), accIt.Hash())
 					}
+					log.Trace("Converting account address", "hash", accIt.Hash(), "addr", addr)
 					preimageSeek += int64(len(addr))
 					migrdb.SetCurrentAccountAddress(addr)
 				} else {
@@ -223,7 +417,7 @@ func OverlayVerkleTransition(statedb *state.StateDB) error {
 		}
 		migrdb.SetCurrentPreimageOffset(preimageSeek)
 
-		log.Info("Collected key values from base tree", "count", count, "duration", time.Since(now), "last account", statedb.Database().GetCurrentAccountHash())
+		log.Info("Collected key values from base tree", "count", count, "duration", time.Since(now), "last account hash", statedb.Database().GetCurrentAccountHash(), "last account address", statedb.Database().GetCurrentAccountAddress(), "storage processed", statedb.Database().GetStorageProcessed(), "last storage", statedb.Database().GetCurrentSlotHash())
 
 		// Take all the collected key-values and prepare the new leaf values.
 		// This fires a background routine that will start doing the work that

core/rawdb/accessors_overlay.go

@@ -0,0 +1,30 @@
+// Copyright 2024 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// 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 rawdb
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/ethdb"
+)
+
+func ReadVerkleTransitionState(db ethdb.KeyValueReader, hash common.Hash) ([]byte, error) {
+	return db.Get(transitionStateKey(hash))
+}
+
+func WriteVerkleTransitionState(db ethdb.KeyValueWriter, hash common.Hash, state []byte) error {
+	return db.Put(transitionStateKey(hash), state)
+}

core/rawdb/schema.go

@@ -129,6 +129,8 @@ var (
 
 	CliqueSnapshotPrefix = []byte("clique-")
 
+	VerkleTransitionStatePrefix = []byte("verkle-transition-state-")
+
 	preimageCounter    = metrics.NewRegisteredCounter("db/preimage/total", nil)
 	preimageHitCounter = metrics.NewRegisteredCounter("db/preimage/hits", nil)
 )
@@ -262,6 +264,11 @@ func storageTrieNodeKey(accountHash common.Hash, path []byte) []byte {
 	return append(append(trieNodeStoragePrefix, accountHash.Bytes()...), path...)
 }
 
+// transitionStateKey = transitionStatusKey + hash
+func transitionStateKey(hash common.Hash) []byte {
+	return append(VerkleTransitionStatePrefix, hash.Bytes()...)
+}
+
 // IsLegacyTrieNode reports whether a provided database entry is a legacy trie
 // node. The characteristics of legacy trie node are:
 // - the key length is 32 bytes

core/state/database.go

@@ -17,8 +17,11 @@
 package state
 
 import (
+	"bytes"
+	"encoding/gob"
 	"errors"
 	"fmt"
+	"sync"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/lru"
@@ -26,6 +29,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/trie"
 	"github.com/ethereum/go-ethereum/trie/trienode"
@@ -64,7 +68,7 @@ type Database interface {
 	// TrieDB retrieves the low level trie database used for data storage.
 	TrieDB() *trie.Database
 
-	StartVerkleTransition(originalRoot, translatedRoot common.Hash, chainConfig *params.ChainConfig, cancunTime *uint64)
+	StartVerkleTransition(originalRoot, translatedRoot common.Hash, chainConfig *params.ChainConfig, cancunTime *uint64, root common.Hash)
 
 	ReorgThroughVerkleTransition()
 
@@ -74,7 +78,9 @@ type Database interface {
 
 	Transitioned() bool
 
-	SetCurrentSlotHash(hash common.Hash)
+	InitTransitionStatus(bool, bool)
+
+	SetCurrentSlotHash(common.Hash)
 
 	GetCurrentAccountAddress() *common.Address
 
@@ -94,7 +100,15 @@ type Database interface {
 
 	AddRootTranslation(originalRoot, translatedRoot common.Hash)
 
-	SetLastMerkleRoot(root common.Hash)
+	SetLastMerkleRoot(common.Hash)
+
+	SaveTransitionState(common.Hash)
+
+	LoadTransitionState(common.Hash)
+
+	LockCurrentTransitionState()
+
+	UnLockCurrentTransitionState()
 }
 
 // Trie is a Ethereum Merkle Patricia trie.
@@ -187,6 +201,7 @@ func NewDatabaseWithConfig(db ethdb.Database, config *trie.Config) Database {
 		codeCache:              lru.NewSizeConstrainedCache[common.Hash, []byte](codeCacheSize),
 		triedb:                 trie.NewDatabaseWithConfig(db, config),
 		addrToPoint:            utils.NewPointCache(),
+		TransitionStatePerRoot: lru.NewBasicLRU[common.Hash, *TransitionState](100),
 	}
 }
 
@@ -198,20 +213,20 @@ func NewDatabaseWithNodeDB(db ethdb.Database, triedb *trie.Database) Database {
 		codeCache:              lru.NewSizeConstrainedCache[common.Hash, []byte](codeCacheSize),
 		triedb:                 triedb,
 		addrToPoint:            utils.NewPointCache(),
-		ended:         triedb.IsVerkle(),
+		TransitionStatePerRoot: lru.NewBasicLRU[common.Hash, *TransitionState](100),
 	}
 }
 
 func (db *cachingDB) InTransition() bool {
-	return db.started && !db.ended
+	return db.CurrentTransitionState != nil && db.CurrentTransitionState.Started && !db.CurrentTransitionState.Ended
 }
 
 func (db *cachingDB) Transitioned() bool {
-	return db.ended
+	return db.CurrentTransitionState != nil && db.CurrentTransitionState.Ended
 }
 
 // Fork implements the fork
-func (db *cachingDB) StartVerkleTransition(originalRoot, translatedRoot common.Hash, chainConfig *params.ChainConfig, pragueTime *uint64) {
+func (db *cachingDB) StartVerkleTransition(originalRoot, translatedRoot common.Hash, chainConfig *params.ChainConfig, pragueTime *uint64, root common.Hash) {
 	fmt.Println(`
 	__________.__                       .__                .__                   __       .__                               .__          ____         
 	\__    ___|  |__   ____        ____ |  |   ____ ______ |  |__ _____    _____/  |_     |  |__ _____    ______    __  _  _|__| ____   / ___\ ______
@@ -219,24 +234,35 @@ func (db *cachingDB) StartVerkleTransition(originalRoot, translatedRoot common.H
 	  |    |  |   Y  \  ___/     \  ___/|  |_\  ___/|  |_> |   Y  \/ __ \|   |  |  |      |   Y  \/ __ \_\___ \      \     /|  |   |  \\___  /\___ \
 	  |____|  |___|  /\___        \___  |____/\___  |   __/|___|  (____  |___|  |__|      |___|  (____  /_____/       \/\_/ |__|___|  /_____//_____/
                                                     |__|`)
-	db.started = true
+	db.CurrentTransitionState = &TransitionState{
-	db.ended = false
+		Started: true,
+		// initialize so that the first storage-less accounts are processed
+		StorageProcessed: true,
+	}
 	// db.AddTranslation(originalRoot, translatedRoot)
 	db.baseRoot = originalRoot
-	// initialize so that the first storage-less accounts are processed
+
-	db.StorageProcessed = true
+	// Reinitialize values in case of a reorg
 	if pragueTime != nil {
 		chainConfig.PragueTime = pragueTime
 	}
 }
 
 func (db *cachingDB) ReorgThroughVerkleTransition() {
-	db.ended, db.started = false, false
+	log.Warn("trying to reorg through the transition, which makes no sense at this point")
+}
+
+func (db *cachingDB) InitTransitionStatus(started, ended bool) {
+	db.CurrentTransitionState = &TransitionState{
+		Ended:   ended,
+		Started: started,
+		// TODO add other fields when we handle mid-transition interrupts
+	}
 }
 
 func (db *cachingDB) EndVerkleTransition() {
-	if !db.started {
+	if !db.CurrentTransitionState.Started {
-		db.started = true
+		db.CurrentTransitionState.Started = true
 	}
 
 	fmt.Println(`
@@ -246,7 +272,36 @@ func (db *cachingDB) EndVerkleTransition() {
 	  |    |  |   Y  \  ___/     \  ___/|  |_\  ___/|  |_> |   Y  \/ __ \|   |  |  |      |   Y  \/ __ \_\___ \     |  |__/ __ \|   |  / /_/ \  ___// /_/ |
 	  |____|  |___|  /\___        \___  |____/\___  |   __/|___|  (____  |___|  |__|      |___|  (____  /_____/     |____(____  |___|  \____ |\___  \____ |
                                                     |__|`)
-	db.ended = true
+	db.CurrentTransitionState.Ended = true
+}
+
+type TransitionState struct {
+	CurrentAccountAddress *common.Address // addresss of the last translated account
+	CurrentSlotHash       common.Hash     // hash of the last translated storage slot
+	CurrentPreimageOffset int64           // next byte to read from the preimage file
+	Started, Ended        bool
+
+	// Mark whether the storage for an account has been processed. This is useful if the
+	// maximum number of leaves of the conversion is reached before the whole storage is
+	// processed.
+	StorageProcessed bool
+}
+
+func (ts *TransitionState) Copy() *TransitionState {
+	ret := &TransitionState{
+		Started:               ts.Started,
+		Ended:                 ts.Ended,
+		CurrentSlotHash:       ts.CurrentSlotHash,
+		CurrentPreimageOffset: ts.CurrentPreimageOffset,
+		StorageProcessed:      ts.StorageProcessed,
+	}
+
+	if ts.CurrentAccountAddress != nil {
+		ret.CurrentAccountAddress = &common.Address{}
+		copy(ret.CurrentAccountAddress[:], ts.CurrentAccountAddress[:])
+	}
+
+	return ret
 }
 
 type cachingDB struct {
@@ -255,22 +310,16 @@ type cachingDB struct {
 	codeCache     *lru.SizeConstrainedCache[common.Hash, []byte]
 	triedb        *trie.Database
 
-	// Verkle specific fields
+	// Transition-specific fields
 	// TODO ensure that this info is in the DB
-	started, ended bool
 	LastMerkleRoot         common.Hash // root hash of the read-only base tree
+	CurrentTransitionState *TransitionState
+	TransitionStatePerRoot lru.BasicLRU[common.Hash, *TransitionState]
+	transitionStateLock    sync.Mutex
 
 	addrToPoint *utils.PointCache
 
 	baseRoot common.Hash // hash of the read-only base tree
-	CurrentAccountAddress *common.Address // addresss of the last translated account
-	CurrentSlotHash       common.Hash     // hash of the last translated storage slot
-	CurrentPreimageOffset int64           // next byte to read from the preimage file
-
-	// Mark whether the storage for an account has been processed. This is useful if the
-	// maximum number of leaves of the conversion is reached before the whole storage is
-	// processed.
-	StorageProcessed bool
 }
 
 func (db *cachingDB) openMPTTrie(root common.Hash) (Trie, error) {
@@ -284,14 +333,14 @@ func (db *cachingDB) openMPTTrie(root common.Hash) (Trie, error) {
 func (db *cachingDB) openVKTrie(root common.Hash) (Trie, error) {
 	payload, err := db.DiskDB().Get(trie.FlatDBVerkleNodeKeyPrefix)
 	if err != nil {
-		return trie.NewVerkleTrie(verkle.New(), db.triedb, db.addrToPoint, db.ended), nil
+		return trie.NewVerkleTrie(verkle.New(), db.triedb, db.addrToPoint, db.CurrentTransitionState.Ended), nil
 	}
 
 	r, err := verkle.ParseNode(payload, 0)
 	if err != nil {
 		panic(err)
 	}
-	return trie.NewVerkleTrie(r, db.triedb, db.addrToPoint, db.ended), err
+	return trie.NewVerkleTrie(r, db.triedb, db.addrToPoint, db.CurrentTransitionState.Ended), err
 }
 
 // OpenTrie opens the main account trie at a specific root hash.
@@ -300,19 +349,22 @@ func (db *cachingDB) OpenTrie(root common.Hash) (Trie, error) {
 		mpt Trie
 		err error
 	)
+	fmt.Printf("opening trie with root %x, %v %v\n", root, db.InTransition(), db.Transitioned())
 
 	// TODO separate both cases when I can be certain that it won't
 	// find a Verkle trie where is expects a Transitoion trie.
-	if db.started || db.ended {
+	if db.InTransition() || db.Transitioned() {
 		// NOTE this is a kaustinen-only change, it will break replay
 		vkt, err := db.openVKTrie(root)
 		if err != nil {
+			log.Error("failed to open the vkt", "err", err)
 			return nil, err
 		}
 
 		// If the verkle conversion has ended, return a single
 		// verkle trie.
-		if db.ended {
+		if db.CurrentTransitionState.Ended {
+			log.Debug("transition ended, returning a simple verkle tree")
 			return vkt, nil
 		}
 
@@ -320,6 +372,7 @@ func (db *cachingDB) OpenTrie(root common.Hash) (Trie, error) {
 		// trie and an overlay, verkle trie.
 		mpt, err = db.openMPTTrie(db.baseRoot)
 		if err != nil {
+			log.Error("failed to open the mpt", "err", err, "root", db.baseRoot)
 			return nil, err
 		}
 
@@ -345,7 +398,7 @@ func (db *cachingDB) openStorageMPTrie(stateRoot common.Hash, address common.Add
 // OpenStorageTrie opens the storage trie of an account
 func (db *cachingDB) OpenStorageTrie(stateRoot common.Hash, address common.Address, root common.Hash, self Trie) (Trie, error) {
 	// TODO this should only return a verkle tree
-	if db.ended {
+	if db.Transitioned() {
 		mpt, err := db.openStorageMPTrie(types.EmptyRootHash, address, common.Hash{}, self)
 		if err != nil {
 			return nil, err
@@ -361,7 +414,8 @@ func (db *cachingDB) OpenStorageTrie(stateRoot common.Hash, address common.Addre
 			panic("unexpected trie type")
 		}
 	}
-	if db.started {
+	if db.InTransition() {
+		fmt.Printf("OpenStorageTrie during transition, state root=%x root=%x\n", stateRoot, root)
 		mpt, err := db.openStorageMPTrie(db.LastMerkleRoot, address, root, nil)
 		if err != nil {
 			return nil, err
@@ -374,7 +428,7 @@ func (db *cachingDB) OpenStorageTrie(stateRoot common.Hash, address common.Addre
 		case *trie.TransitionTrie:
 			return trie.NewTransitionTree(mpt.(*trie.SecureTrie), self.Overlay(), true), nil
 		default:
-			panic("unexpected trie type")
+			return nil, errors.New("expected a verkle account tree, and found another type")
 		}
 	}
 	mpt, err := db.openStorageMPTrie(stateRoot, address, root, nil)
@@ -451,48 +505,128 @@ func (db *cachingDB) GetTreeKeyHeader(addr []byte) *verkle.Point {
 }
 
 func (db *cachingDB) SetCurrentAccountAddress(addr common.Address) {
-	db.CurrentAccountAddress = &addr
+	db.CurrentTransitionState.CurrentAccountAddress = &addr
 }
 
 func (db *cachingDB) GetCurrentAccountHash() common.Hash {
 	var addrHash common.Hash
-	if db.CurrentAccountAddress != nil {
+	if db.CurrentTransitionState.CurrentAccountAddress != nil {
-		addrHash = crypto.Keccak256Hash(db.CurrentAccountAddress[:])
+		addrHash = crypto.Keccak256Hash(db.CurrentTransitionState.CurrentAccountAddress[:])
 	}
 	return addrHash
 }
 
 func (db *cachingDB) GetCurrentAccountAddress() *common.Address {
-	return db.CurrentAccountAddress
+	return db.CurrentTransitionState.CurrentAccountAddress
 }
 
 func (db *cachingDB) GetCurrentPreimageOffset() int64 {
-	return db.CurrentPreimageOffset
+	return db.CurrentTransitionState.CurrentPreimageOffset
 }
 
 func (db *cachingDB) SetCurrentPreimageOffset(offset int64) {
-	db.CurrentPreimageOffset = offset
+	db.CurrentTransitionState.CurrentPreimageOffset = offset
 }
 
 func (db *cachingDB) SetCurrentSlotHash(hash common.Hash) {
-	db.CurrentSlotHash = hash
+	db.CurrentTransitionState.CurrentSlotHash = hash
 }
 
 func (db *cachingDB) GetCurrentSlotHash() common.Hash {
-	return db.CurrentSlotHash
+	return db.CurrentTransitionState.CurrentSlotHash
 }
 
 func (db *cachingDB) SetStorageProcessed(processed bool) {
-	db.StorageProcessed = processed
+	db.CurrentTransitionState.StorageProcessed = processed
 }
 
 func (db *cachingDB) GetStorageProcessed() bool {
-	return db.StorageProcessed
+	return db.CurrentTransitionState.StorageProcessed
 }
 
 func (db *cachingDB) AddRootTranslation(originalRoot, translatedRoot common.Hash) {
 }
 
-func (db *cachingDB) SetLastMerkleRoot(root common.Hash) {
+func (db *cachingDB) SetLastMerkleRoot(merkleRoot common.Hash) {
-	db.LastMerkleRoot = root
+	db.LastMerkleRoot = merkleRoot
+}
+
+func (db *cachingDB) SaveTransitionState(root common.Hash) {
+	db.transitionStateLock.Lock()
+	defer db.transitionStateLock.Unlock()
+	if db.CurrentTransitionState != nil {
+		var buf bytes.Buffer
+		enc := gob.NewEncoder(&buf)
+		err := enc.Encode(db.CurrentTransitionState)
+		if err != nil {
+			log.Error("failed to encode transition state", "err", err)
+			return
+		}
+
+		if !db.TransitionStatePerRoot.Contains(root) {
+			// Copy so that the address pointer isn't updated after
+			// it has been saved.
+			db.TransitionStatePerRoot.Add(root, db.CurrentTransitionState.Copy())
+
+			rawdb.WriteVerkleTransitionState(db.DiskDB(), root, buf.Bytes())
+		}
+
+		log.Debug("saving transition state", "storage processed", db.CurrentTransitionState.StorageProcessed, "addr", db.CurrentTransitionState.CurrentAccountAddress, "slot hash", db.CurrentTransitionState.CurrentSlotHash, "root", root, "ended", db.CurrentTransitionState.Ended, "started", db.CurrentTransitionState.Started)
+	}
+}
+
+func (db *cachingDB) LoadTransitionState(root common.Hash) {
+	db.transitionStateLock.Lock()
+	defer db.transitionStateLock.Unlock()
+	// Try to get the transition state from the cache and
+	// the DB if it's not there.
+	ts, ok := db.TransitionStatePerRoot.Get(root)
+	if !ok {
+		// Not in the cache, try getting it from the DB
+		data, err := rawdb.ReadVerkleTransitionState(db.DiskDB(), root)
+		if err != nil {
+			log.Error("failed to read transition state", "err", err)
+			return
+		}
+
+		// if a state could be read from the db, attempt to decode it
+		if len(data) > 0 {
+			var (
+				newts TransitionState
+				buf   = bytes.NewBuffer(data[:])
+				dec   = gob.NewDecoder(buf)
+			)
+			// Decode transition state
+			err = dec.Decode(&newts)
+			if err != nil {
+				log.Error("failed to decode transition state", "err", err)
+				return
+			}
+			ts = &newts
+		}
+
+		// Fallback that should only happen before the transition
+		if ts == nil {
+			// Initialize the first transition state, with the "ended"
+			// field set to true if the database was created
+			// as a verkle database.
+			log.Debug("no transition state found, starting fresh", "is verkle", db.triedb.IsVerkle())
+			// Start with a fresh state
+			ts = &TransitionState{Ended: db.triedb.IsVerkle()}
+		}
+	}
+
+	// Copy so that the CurrentAddress pointer in the map
+	// doesn't get overwritten.
+	db.CurrentTransitionState = ts.Copy()
+
+	log.Debug("loaded transition state", "storage processed", db.CurrentTransitionState.StorageProcessed, "addr", db.CurrentTransitionState.CurrentAccountAddress, "slot hash", db.CurrentTransitionState.CurrentSlotHash, "root", root, "ended", db.CurrentTransitionState.Ended, "started", db.CurrentTransitionState.Started)
+}
+
+func (db *cachingDB) LockCurrentTransitionState() {
+	db.transitionStateLock.Lock()
+}
+
+func (db *cachingDB) UnLockCurrentTransitionState() {
+	db.transitionStateLock.Unlock()
 }

core/state/statedb.go

@@ -176,10 +176,11 @@ func New(root common.Hash, db Database, snaps *snapshot.Tree) (*StateDB, error)
 	if tr.IsVerkle() {
 		sdb.witness = sdb.NewAccessWitness()
 	}
-	// if sdb.snaps != nil {
+	if sdb.snaps != nil {
 		// 	if sdb.snap = sdb.snaps.Snapshot(root); sdb.snap == nil {
 		// 	}
-	// }
+		sdb.snap = sdb.snaps.Snapshot(root)
+	}
 	return sdb, nil
 }
 
@@ -1317,7 +1318,7 @@ func (s *StateDB) Commit(block uint64, deleteEmptyObjects bool) (common.Hash, er
 			// - head layer is paired with HEAD state
 			// - head-1 layer is paired with HEAD-1 state
 			// - head-127 layer(bottom-most diff layer) is paired with HEAD-127 state
-			if err := s.snaps.Cap(root, 128); err != nil {
+			if err := s.snaps.Cap(root, 8192); err != nil {
 				log.Warn("Failed to cap snapshot tree", "root", root, "layers", 128, "err", err)
 			}
 		}

core/state/trie_prefetcher.go

@@ -302,7 +302,7 @@ func (sf *subfetcher) loop() {
 		}
 		sf.trie = trie
 	} else {
-		trie, err := sf.db.OpenStorageTrie(sf.state, sf.addr, sf.root, nil /* safe to set to nil for now, as there is no prefetcher for verkle */)
+		trie, err := sf.db.OpenStorageTrie(sf.state, sf.addr, sf.root, sf.trie)
 		if err != nil {
 			log.Warn("Trie prefetcher failed opening trie", "root", sf.root, "err", err)
 			return

core/state_processor.go

@@ -21,9 +21,6 @@ import (
 	"errors"
 	"fmt"
 	"math/big"
-	"runtime"
-	"sync"
-	"time"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/consensus"
@@ -34,10 +31,6 @@ import (
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/trie"
-	tutils "github.com/ethereum/go-ethereum/trie/utils"
-	"github.com/ethereum/go-verkle"
-	"github.com/holiman/uint256"
 )
 
 // StateProcessor is a basic Processor, which takes care of transitioning
@@ -113,11 +106,6 @@ func (p *StateProcessor) Process(block *types.Block, statedb *state.StateDB, cfg
 		return nil, nil, 0, errors.New("withdrawals before shanghai")
 	}
 
-	// Perform the overlay transition, if relevant
-	if err := OverlayVerkleTransition(statedb); err != nil {
-		return nil, nil, 0, fmt.Errorf("error performing verkle overlay transition: %w", err)
-	}
-
 	// Finalize the block, applying any consensus engine specific extras (e.g. block rewards)
 	p.engine.Finalize(p.bc, header, statedb, block.Transactions(), block.Uncles(), withdrawals)
 
@@ -192,185 +180,6 @@ func ApplyTransaction(config *params.ChainConfig, bc ChainContext, author *commo
 	return applyTransaction(msg, config, gp, statedb, header.Number, header.Hash(), tx, usedGas, vmenv)
 }
 
-var zeroTreeIndex uint256.Int
-
-// keyValueMigrator is a helper module that collects key-values from the overlay-tree migration for Verkle Trees.
-// It assumes that the walk of the base tree is done in address-order, so it exploit that fact to
-// collect the key-values in a way that is efficient.
-type keyValueMigrator struct {
-	// leafData contains the values for the future leaf for a particular VKT branch.
-	leafData []migratedKeyValue
-
-	// When prepare() is called, it will start a background routine that will process the leafData
-	// saving the result in newLeaves to be used by migrateCollectedKeyValues(). The background
-	// routine signals that it is done by closing processingReady.
-	processingReady chan struct{}
-	newLeaves       []verkle.LeafNode
-	prepareErr      error
-}
-
-func newKeyValueMigrator() *keyValueMigrator {
-	// We do initialize the VKT config since prepare() might indirectly make multiple GetConfig() calls
-	// in different goroutines when we never called GetConfig() before, causing a race considering the way
-	// that `config` is designed in go-verkle.
-	// TODO: jsign as a fix for this in the PR where we move to a file-less precomp, since it allows safe
-	//       concurrent calls to GetConfig(). When that gets merged, we can remove this line.
-	_ = verkle.GetConfig()
-	return &keyValueMigrator{
-		processingReady: make(chan struct{}),
-		leafData:        make([]migratedKeyValue, 0, 10_000),
-	}
-}
-
-type migratedKeyValue struct {
-	branchKey    branchKey
-	leafNodeData verkle.BatchNewLeafNodeData
-}
-type branchKey struct {
-	addr      common.Address
-	treeIndex uint256.Int
-}
-
-func newBranchKey(addr []byte, treeIndex *uint256.Int) branchKey {
-	var sk branchKey
-	copy(sk.addr[:], addr)
-	sk.treeIndex = *treeIndex
-	return sk
-}
-
-func (kvm *keyValueMigrator) addStorageSlot(addr []byte, slotNumber []byte, slotValue []byte) {
-	treeIndex, subIndex := tutils.GetTreeKeyStorageSlotTreeIndexes(slotNumber)
-	leafNodeData := kvm.getOrInitLeafNodeData(newBranchKey(addr, treeIndex))
-	leafNodeData.Values[subIndex] = slotValue
-}
-
-func (kvm *keyValueMigrator) addAccount(addr []byte, acc *types.StateAccount) {
-	leafNodeData := kvm.getOrInitLeafNodeData(newBranchKey(addr, &zeroTreeIndex))
-
-	var version [verkle.LeafValueSize]byte
-	leafNodeData.Values[tutils.VersionLeafKey] = version[:]
-
-	var balance [verkle.LeafValueSize]byte
-	for i, b := range acc.Balance.Bytes() {
-		balance[len(acc.Balance.Bytes())-1-i] = b
-	}
-	leafNodeData.Values[tutils.BalanceLeafKey] = balance[:]
-
-	var nonce [verkle.LeafValueSize]byte
-	binary.LittleEndian.PutUint64(nonce[:8], acc.Nonce)
-	leafNodeData.Values[tutils.NonceLeafKey] = nonce[:]
-
-	leafNodeData.Values[tutils.CodeHashLeafKey] = acc.CodeHash[:]
-}
-
-func (kvm *keyValueMigrator) addAccountCode(addr []byte, codeSize uint64, chunks []byte) {
-	leafNodeData := kvm.getOrInitLeafNodeData(newBranchKey(addr, &zeroTreeIndex))
-
-	// Save the code size.
-	var codeSizeBytes [verkle.LeafValueSize]byte
-	binary.LittleEndian.PutUint64(codeSizeBytes[:8], codeSize)
-	leafNodeData.Values[tutils.CodeSizeLeafKey] = codeSizeBytes[:]
-
-	// The first 128 chunks are stored in the account header leaf.
-	for i := 0; i < 128 && i < len(chunks)/32; i++ {
-		leafNodeData.Values[byte(128+i)] = chunks[32*i : 32*(i+1)]
-	}
-
-	// Potential further chunks, have their own leaf nodes.
-	for i := 128; i < len(chunks)/32; {
-		treeIndex, _ := tutils.GetTreeKeyCodeChunkIndices(uint256.NewInt(uint64(i)))
-		leafNodeData := kvm.getOrInitLeafNodeData(newBranchKey(addr, treeIndex))
-
-		j := i
-		for ; (j-i) < 256 && j < len(chunks)/32; j++ {
-			leafNodeData.Values[byte((j-128)%256)] = chunks[32*j : 32*(j+1)]
-		}
-		i = j
-	}
-}
-
-func (kvm *keyValueMigrator) getOrInitLeafNodeData(bk branchKey) *verkle.BatchNewLeafNodeData {
-	// Remember that keyValueMigration receives actions ordered by (address, subtreeIndex).
-	// This means that we can assume that the last element of leafData is the one that we
-	// are looking for, or that we need to create a new one.
-	if len(kvm.leafData) == 0 || kvm.leafData[len(kvm.leafData)-1].branchKey != bk {
-		kvm.leafData = append(kvm.leafData, migratedKeyValue{
-			branchKey: bk,
-			leafNodeData: verkle.BatchNewLeafNodeData{
-				Stem:   nil, // It will be calculated in the prepare() phase, since it's CPU heavy.
-				Values: make(map[byte][]byte),
-			},
-		})
-	}
-	return &kvm.leafData[len(kvm.leafData)-1].leafNodeData
-}
-
-func (kvm *keyValueMigrator) prepare() {
-	// We fire a background routine to process the leafData and save the result in newLeaves.
-	// The background routine signals that it is done by closing processingReady.
-	go func() {
-		// Step 1: We split kvm.leafData in numBatches batches, and we process each batch in a separate goroutine.
-		//         This fills each leafNodeData.Stem with the correct value.
-		var wg sync.WaitGroup
-		batchNum := runtime.NumCPU()
-		batchSize := (len(kvm.leafData) + batchNum - 1) / batchNum
-		for i := 0; i < len(kvm.leafData); i += batchSize {
-			start := i
-			end := i + batchSize
-			if end > len(kvm.leafData) {
-				end = len(kvm.leafData)
-			}
-			wg.Add(1)
-
-			batch := kvm.leafData[start:end]
-			go func() {
-				defer wg.Done()
-				var currAddr common.Address
-				var currPoint *verkle.Point
-				for i := range batch {
-					if batch[i].branchKey.addr != currAddr {
-						currAddr = batch[i].branchKey.addr
-						currPoint = tutils.EvaluateAddressPoint(currAddr[:])
-					}
-					stem := tutils.GetTreeKeyWithEvaluatedAddess(currPoint, &batch[i].branchKey.treeIndex, 0)
-					stem = stem[:verkle.StemSize]
-					batch[i].leafNodeData.Stem = stem
-				}
-			}()
-		}
-		wg.Wait()
-
-		// Step 2: Now that we have all stems (i.e: tree keys) calculated, we can create the new leaves.
-		nodeValues := make([]verkle.BatchNewLeafNodeData, len(kvm.leafData))
-		for i := range kvm.leafData {
-			nodeValues[i] = kvm.leafData[i].leafNodeData
-		}
-
-		// Create all leaves in batch mode so we can optimize cryptography operations.
-		kvm.newLeaves, kvm.prepareErr = verkle.BatchNewLeafNode(nodeValues)
-		close(kvm.processingReady)
-	}()
-}
-
-func (kvm *keyValueMigrator) migrateCollectedKeyValues(tree *trie.VerkleTrie) error {
-	now := time.Now()
-	<-kvm.processingReady
-	if kvm.prepareErr != nil {
-		return fmt.Errorf("failed to prepare key values: %w", kvm.prepareErr)
-	}
-	log.Info("Prepared key values from base tree", "duration", time.Since(now))
-
-	// Insert into the tree.
-	if err := tree.InsertMigratedLeaves(kvm.newLeaves); err != nil {
-		return fmt.Errorf("failed to insert migrated leaves: %w", err)
-	}
-
-	return nil
-}
-
-// InsertBlockHashHistoryAtEip2935Fork handles the insertion of all previous 256
-// blocks on the eip2935 activation block. It also adds the account header of the
-// history contract to the witness.
 func InsertBlockHashHistoryAtEip2935Fork(statedb *state.StateDB, prevNumber uint64, prevHash common.Hash, chain consensus.ChainHeaderReader) {
 	// Make sure that the historical contract is added to the witness
 	statedb.Witness().TouchFullAccount(params.HistoryStorageAddress[:], true)

eth/api_debug.go

@@ -17,7 +17,9 @@
 package eth
 
 import (
+	"bytes"
 	"context"
+	"encoding/gob"
 	"errors"
 	"fmt"
 	"time"
@@ -432,3 +434,41 @@ func (api *DebugAPI) SetTrieFlushInterval(interval string) error {
 func (api *DebugAPI) GetTrieFlushInterval() string {
 	return api.eth.blockchain.GetTrieFlushInterval().String()
 }
+
+type ConversionStatusResult struct {
+	Started bool `json:"started"`
+	Ended   bool `json:"ended"`
+}
+
+func (api *DebugAPI) ConversionStatus(ctx context.Context, blockNrOrHash rpc.BlockNumberOrHash) (*ConversionStatusResult, error) {
+	block, err := api.eth.APIBackend.BlockByNumberOrHash(ctx, blockNrOrHash)
+	if err != nil {
+		return nil, err
+	}
+	data, err := rawdb.ReadVerkleTransitionState(api.eth.ChainDb(), block.Root())
+	if err != nil {
+		if err.Error() == "pebble: not found" {
+			return &ConversionStatusResult{}, nil
+		}
+		return nil, err
+	}
+	log.Info("found entry", "data", data)
+	if len(data) == 0 {
+		log.Info("found no data")
+		// started and ended will be false as no conversion has started
+		return &ConversionStatusResult{}, nil
+	}
+
+	var (
+		ts  state.TransitionState
+		buf = bytes.NewBuffer(data[:])
+		dec = gob.NewDecoder(buf)
+	)
+	// Decode transition state
+	err = dec.Decode(&ts)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decode transition state, err=%v", err)
+	}
+
+	return &ConversionStatusResult{Started: ts.Started, Ended: ts.Ended}, nil
+}

eth/backend.go

@@ -201,6 +201,12 @@ func New(stack *node.Node, config *ethconfig.Config) (*Ethereum, error) {
 	if config.OverridePrague != nil {
 		overrides.OverridePrague = config.OverridePrague
 	}
+	if config.OverrideProofInBlock != nil {
+		overrides.OverrideProofInBlock = config.OverrideProofInBlock
+	}
+	if config.OverrideOverlayStride != nil {
+		overrides.OverrideOverlayStride = config.OverrideOverlayStride
+	}
 	eth.blockchain, err = core.NewBlockChain(chainDb, cacheConfig, config.Genesis, &overrides, eth.engine, vmConfig, eth.shouldPreserve, &config.TxLookupLimit)
 	if err != nil {
 		return nil, err

eth/catalyst/api.go

@@ -532,13 +532,9 @@ func (api *ConsensusAPI) newPayload(params engine.ExecutableData, versionedHashe
 	if api.eth.BlockChain().Config().IsPrague(block.Number(), block.Time()) && !api.eth.BlockChain().Config().IsPrague(parent.Number(), parent.Time()) {
 		parent := api.eth.BlockChain().GetHeaderByNumber(block.NumberU64() - 1)
 		if !api.eth.BlockChain().Config().IsPrague(parent.Number, parent.Time) {
-			api.eth.BlockChain().StartVerkleTransition(parent.Root, common.Hash{}, api.eth.BlockChain().Config(), nil)
+			api.eth.BlockChain().StartVerkleTransition(parent.Root, common.Hash{}, api.eth.BlockChain().Config(), nil, parent.Root)
 		}
 	}
-	// Reset db merge state in case of a reorg
-	if !api.eth.BlockChain().Config().IsPrague(block.Number(), block.Time()) {
-		api.eth.BlockChain().ReorgThroughVerkleTransition()
-	}
 	// Another cornercase: if the node is in snap sync mode, but the CL client
 	// tries to make it import a block. That should be denied as pushing something
 	// into the database directly will conflict with the assumptions of snap sync

eth/ethconfig/config.go

@@ -158,6 +158,12 @@ type Config struct {
 
 	// OverrideVerkle (TODO: remove after the fork)
 	OverridePrague *uint64 `toml:",omitempty"`
+
+	// OverrideProofInBlock
+	OverrideProofInBlock *bool `toml:",omitempty"`
+
+	// OverrideOverlayStride
+	OverrideOverlayStride *uint64 `toml:",omitempty"`
 }
 
 // CreateConsensusEngine creates a consensus engine for the given chain config.

light/trie.go

@@ -101,7 +101,7 @@ func (db *odrDatabase) DiskDB() ethdb.KeyValueStore {
 	panic("not implemented")
 }
 
-func (db *odrDatabase) StartVerkleTransition(originalRoot common.Hash, translatedRoot common.Hash, chainConfig *params.ChainConfig, _ *uint64) {
+func (db *odrDatabase) StartVerkleTransition(originalRoot common.Hash, translatedRoot common.Hash, chainConfig *params.ChainConfig, _ *uint64, _ common.Hash) {
 	panic("not implemented") // TODO: Implement
 }
 
@@ -121,7 +121,11 @@ func (db *odrDatabase) Transitioned() bool {
 	panic("not implemented") // TODO: Implement
 }
 
-func (db *odrDatabase) SetCurrentSlotHash(hash common.Hash) {
+func (db *odrDatabase) InitTransitionStatus(bool, bool) {
+	panic("not implemented") // TODO: Implement
+}
+
+func (db *odrDatabase) SetCurrentSlotHash(common.Hash) {
 	panic("not implemented") // TODO: Implement
 }
 
@@ -129,7 +133,7 @@ func (db *odrDatabase) GetCurrentAccountAddress() *common.Address {
 	panic("not implemented") // TODO: Implement
 }
 
-func (db *odrDatabase) SetCurrentAccountAddress(_ common.Address) {
+func (db *odrDatabase) SetCurrentAccountAddress(common.Address) {
 	panic("not implemented") // TODO: Implement
 }
 
@@ -141,7 +145,7 @@ func (db *odrDatabase) GetCurrentSlotHash() common.Hash {
 	panic("not implemented") // TODO: Implement
 }
 
-func (db *odrDatabase) SetStorageProcessed(_ bool) {
+func (db *odrDatabase) SetStorageProcessed(bool) {
 	panic("not implemented") // TODO: Implement
 }
 
@@ -153,15 +157,30 @@ func (db *odrDatabase) GetCurrentPreimageOffset() int64 {
 	panic("not implemented") // TODO: Implement
 }
 
-func (db *odrDatabase) SetCurrentPreimageOffset(_ int64) {
+func (db *odrDatabase) SetCurrentPreimageOffset(int64) {
 	panic("not implemented") // TODO: Implement
 }
 
-func (db *odrDatabase) AddRootTranslation(originalRoot common.Hash, translatedRoot common.Hash) {
+func (db *odrDatabase) AddRootTranslation(common.Hash, common.Hash) {
 	panic("not implemented") // TODO: Implement
 }
 
-func (db *odrDatabase) SetLastMerkleRoot(root common.Hash) {
+func (db *odrDatabase) SetLastMerkleRoot(common.Hash) {
+	panic("not implemented") // TODO: Implement
+}
+
+func (db *odrDatabase) SaveTransitionState(common.Hash) {
+	panic("not implemented") // TODO: Implement
+}
+
+func (db *odrDatabase) LoadTransitionState(common.Hash) {
+	panic("not implemented") // TODO: Implement
+}
+
+func (db *odrDatabase) LockCurrentTransitionState() {
+	panic("not implemented") // TODO: Implement
+}
+func (db *odrDatabase) UnLockCurrentTransitionState() {
 	panic("not implemented") // TODO: Implement
 }
 

miner/worker.go

@@ -852,7 +852,7 @@ func (w *worker) prepareWork(genParams *generateParams) (*environment, error) {
 	if genParams.parentHash != (common.Hash{}) {
 		block := w.chain.GetBlockByHash(genParams.parentHash)
 		if block == nil {
-			return nil, fmt.Errorf("missing parent")
+			return nil, fmt.Errorf("missing parent: %x", genParams.parentHash)
 		}
 		parent = block.Header()
 	}
@@ -894,7 +894,7 @@ func (w *worker) prepareWork(genParams *generateParams) (*environment, error) {
 	if w.chain.Config().IsPrague(header.Number, header.Time) {
 		parent := w.chain.GetHeaderByNumber(header.Number.Uint64() - 1)
 		if !w.chain.Config().IsPrague(parent.Number, parent.Time) {
-			w.chain.StartVerkleTransition(parent.Root, common.Hash{}, w.chain.Config(), nil)
+			w.chain.StartVerkleTransition(parent.Root, common.Hash{}, w.chain.Config(), w.chain.Config().PragueTime, parent.Root)
 		}
 	}
 
@@ -904,9 +904,6 @@ func (w *worker) prepareWork(genParams *generateParams) (*environment, error) {
 	if err != nil {
 		return nil, err
 	}
-	if w.chain.Config().IsPrague(header.Number, header.Time) {
-		core.OverlayVerkleTransition(state)
-	}
 	// Run the consensus preparation with the default or customized consensus engine.
 	if err := w.engine.Prepare(w.chain, header); err != nil {
 		log.Error("Failed to prepare header for sealing", "err", err)

params/config.go

@@ -302,6 +302,7 @@ type ChainConfig struct {
 
 	// Proof in block
 	ProofInBlocks bool   `json:"proofInBlocks,omitempty"`
+	OverlayStride uint64 `json:"overlayStride,omitempty"`
 }
 
 // EthashConfig is the consensus engine configs for proof-of-work based sealing.

trie/transition.go

@@ -17,6 +17,8 @@
 package trie
 
 import (
+	"fmt"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/ethdb"
@@ -62,7 +64,11 @@ func (t *TransitionTrie) GetKey(key []byte) []byte {
 // not be modified by the caller. If a node was not found in the database, a
 // trie.MissingNodeError is returned.
 func (t *TransitionTrie) GetStorage(addr common.Address, key []byte) ([]byte, error) {
-	if val, err := t.overlay.GetStorage(addr, key); len(val) != 0 || err != nil {
+	val, err := t.overlay.GetStorage(addr, key)
+	if err != nil {
+		return nil, fmt.Errorf("get storage from overlay: %s", err)
+	}
+	if len(val) != 0 {
 		return val, nil
 	}
 	// TODO also insert value into overlay