WIP: geth-tavum

1 files changed, 619 insertions, 0 deletions

diff --git a/core/state/snapshot/snapshot.go b/core/state/snapshot/snapshot.go
new file mode 100644
index 0000000..3348685
--- /dev/null
+++ b/core/state/snapshot/snapshot.go
@@ -0,0 +1,619 @@
+// Copyright 2019 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 snapshot implements a journalled, dynamic state dump.
+package snapshot
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"sync"
+	"sync/atomic"
+
+	"github.com/ava-labs/coreth/core/rawdb"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/metrics"
+	"github.com/ethereum/go-ethereum/trie"
+)
+
+var (
+	snapshotCleanAccountHitMeter   = metrics.NewRegisteredMeter("state/snapshot/clean/account/hit", nil)
+	snapshotCleanAccountMissMeter  = metrics.NewRegisteredMeter("state/snapshot/clean/account/miss", nil)
+	snapshotCleanAccountInexMeter  = metrics.NewRegisteredMeter("state/snapshot/clean/account/inex", nil)
+	snapshotCleanAccountReadMeter  = metrics.NewRegisteredMeter("state/snapshot/clean/account/read", nil)
+	snapshotCleanAccountWriteMeter = metrics.NewRegisteredMeter("state/snapshot/clean/account/write", nil)
+
+	snapshotCleanStorageHitMeter   = metrics.NewRegisteredMeter("state/snapshot/clean/storage/hit", nil)
+	snapshotCleanStorageMissMeter  = metrics.NewRegisteredMeter("state/snapshot/clean/storage/miss", nil)
+	snapshotCleanStorageInexMeter  = metrics.NewRegisteredMeter("state/snapshot/clean/storage/inex", nil)
+	snapshotCleanStorageReadMeter  = metrics.NewRegisteredMeter("state/snapshot/clean/storage/read", nil)
+	snapshotCleanStorageWriteMeter = metrics.NewRegisteredMeter("state/snapshot/clean/storage/write", nil)
+
+	snapshotDirtyAccountHitMeter   = metrics.NewRegisteredMeter("state/snapshot/dirty/account/hit", nil)
+	snapshotDirtyAccountMissMeter  = metrics.NewRegisteredMeter("state/snapshot/dirty/account/miss", nil)
+	snapshotDirtyAccountInexMeter  = metrics.NewRegisteredMeter("state/snapshot/dirty/account/inex", nil)
+	snapshotDirtyAccountReadMeter  = metrics.NewRegisteredMeter("state/snapshot/dirty/account/read", nil)
+	snapshotDirtyAccountWriteMeter = metrics.NewRegisteredMeter("state/snapshot/dirty/account/write", nil)
+
+	snapshotDirtyStorageHitMeter   = metrics.NewRegisteredMeter("state/snapshot/dirty/storage/hit", nil)
+	snapshotDirtyStorageMissMeter  = metrics.NewRegisteredMeter("state/snapshot/dirty/storage/miss", nil)
+	snapshotDirtyStorageInexMeter  = metrics.NewRegisteredMeter("state/snapshot/dirty/storage/inex", nil)
+	snapshotDirtyStorageReadMeter  = metrics.NewRegisteredMeter("state/snapshot/dirty/storage/read", nil)
+	snapshotDirtyStorageWriteMeter = metrics.NewRegisteredMeter("state/snapshot/dirty/storage/write", nil)
+
+	snapshotDirtyAccountHitDepthHist = metrics.NewRegisteredHistogram("state/snapshot/dirty/account/hit/depth", nil, metrics.NewExpDecaySample(1028, 0.015))
+	snapshotDirtyStorageHitDepthHist = metrics.NewRegisteredHistogram("state/snapshot/dirty/storage/hit/depth", nil, metrics.NewExpDecaySample(1028, 0.015))
+
+	snapshotFlushAccountItemMeter = metrics.NewRegisteredMeter("state/snapshot/flush/account/item", nil)
+	snapshotFlushAccountSizeMeter = metrics.NewRegisteredMeter("state/snapshot/flush/account/size", nil)
+	snapshotFlushStorageItemMeter = metrics.NewRegisteredMeter("state/snapshot/flush/storage/item", nil)
+	snapshotFlushStorageSizeMeter = metrics.NewRegisteredMeter("state/snapshot/flush/storage/size", nil)
+
+	snapshotBloomIndexTimer = metrics.NewRegisteredResettingTimer("state/snapshot/bloom/index", nil)
+	snapshotBloomErrorGauge = metrics.NewRegisteredGaugeFloat64("state/snapshot/bloom/error", nil)
+
+	snapshotBloomAccountTrueHitMeter  = metrics.NewRegisteredMeter("state/snapshot/bloom/account/truehit", nil)
+	snapshotBloomAccountFalseHitMeter = metrics.NewRegisteredMeter("state/snapshot/bloom/account/falsehit", nil)
+	snapshotBloomAccountMissMeter     = metrics.NewRegisteredMeter("state/snapshot/bloom/account/miss", nil)
+
+	snapshotBloomStorageTrueHitMeter  = metrics.NewRegisteredMeter("state/snapshot/bloom/storage/truehit", nil)
+	snapshotBloomStorageFalseHitMeter = metrics.NewRegisteredMeter("state/snapshot/bloom/storage/falsehit", nil)
+	snapshotBloomStorageMissMeter     = metrics.NewRegisteredMeter("state/snapshot/bloom/storage/miss", nil)
+
+	// ErrSnapshotStale is returned from data accessors if the underlying snapshot
+	// layer had been invalidated due to the chain progressing forward far enough
+	// to not maintain the layer's original state.
+	ErrSnapshotStale = errors.New("snapshot stale")
+
+	// ErrNotCoveredYet is returned from data accessors if the underlying snapshot
+	// is being generated currently and the requested data item is not yet in the
+	// range of accounts covered.
+	ErrNotCoveredYet = errors.New("not covered yet")
+
+	// errSnapshotCycle is returned if a snapshot is attempted to be inserted
+	// that forms a cycle in the snapshot tree.
+	errSnapshotCycle = errors.New("snapshot cycle")
+)
+
+// Snapshot represents the functionality supported by a snapshot storage layer.
+type Snapshot interface {
+	// Root returns the root hash for which this snapshot was made.
+	Root() common.Hash
+
+	// Account directly retrieves the account associated with a particular hash in
+	// the snapshot slim data format.
+	Account(hash common.Hash) (*Account, error)
+
+	// AccountRLP directly retrieves the account RLP associated with a particular
+	// hash in the snapshot slim data format.
+	AccountRLP(hash common.Hash) ([]byte, error)
+
+	// Storage directly retrieves the storage data associated with a particular hash,
+	// within a particular account.
+	Storage(accountHash, storageHash common.Hash) ([]byte, error)
+}
+
+// snapshot is the internal version of the snapshot data layer that supports some
+// additional methods compared to the public API.
+type snapshot interface {
+	Snapshot
+
+	// Parent returns the subsequent layer of a snapshot, or nil if the base was
+	// reached.
+	//
+	// Note, the method is an internal helper to avoid type switching between the
+	// disk and diff layers. There is no locking involved.
+	Parent() snapshot
+
+	// Update creates a new layer on top of the existing snapshot diff tree with
+	// the specified data items.
+	//
+	// Note, the maps are retained by the method to avoid copying everything.
+	Update(blockRoot common.Hash, destructs map[common.Hash]struct{}, accounts map[common.Hash][]byte, storage map[common.Hash]map[common.Hash][]byte) *diffLayer
+
+	// Journal commits an entire diff hierarchy to disk into a single journal entry.
+	// This is meant to be used during shutdown to persist the snapshot without
+	// flattening everything down (bad for reorgs).
+	Journal(buffer *bytes.Buffer) (common.Hash, error)
+
+	// Stale return whether this layer has become stale (was flattened across) or
+	// if it's still live.
+	Stale() bool
+
+	// AccountIterator creates an account iterator over an arbitrary layer.
+	AccountIterator(seek common.Hash) AccountIterator
+
+	// StorageIterator creates a storage iterator over an arbitrary layer.
+	StorageIterator(account common.Hash, seek common.Hash) (StorageIterator, bool)
+}
+
+// SnapshotTree is an Ethereum state snapshot tree. It consists of one persistent
+// base layer backed by a key-value store, on top of which arbitrarily many in-
+// memory diff layers are topped. The memory diffs can form a tree with branching,
+// but the disk layer is singleton and common to all. If a reorg goes deeper than
+// the disk layer, everything needs to be deleted.
+//
+// The goal of a state snapshot is twofold: to allow direct access to account and
+// storage data to avoid expensive multi-level trie lookups; and to allow sorted,
+// cheap iteration of the account/storage tries for sync aid.
+type Tree struct {
+	diskdb ethdb.KeyValueStore      // Persistent database to store the snapshot
+	triedb *trie.Database           // In-memory cache to access the trie through
+	cache  int                      // Megabytes permitted to use for read caches
+	layers map[common.Hash]snapshot // Collection of all known layers
+	lock   sync.RWMutex
+}
+
+// New attempts to load an already existing snapshot from a persistent key-value
+// store (with a number of memory layers from a journal), ensuring that the head
+// of the snapshot matches the expected one.
+//
+// If the snapshot is missing or inconsistent, the entirety is deleted and will
+// be reconstructed from scratch based on the tries in the key-value store, on a
+// background thread.
+func New(diskdb ethdb.KeyValueStore, triedb *trie.Database, cache int, root common.Hash, async bool) *Tree {
+	// Create a new, empty snapshot tree
+	snap := &Tree{
+		diskdb: diskdb,
+		triedb: triedb,
+		cache:  cache,
+		layers: make(map[common.Hash]snapshot),
+	}
+	if !async {
+		defer snap.waitBuild()
+	}
+	// Attempt to load a previously persisted snapshot and rebuild one if failed
+	head, err := loadSnapshot(diskdb, triedb, cache, root)
+	if err != nil {
+		log.Warn("Failed to load snapshot, regenerating", "err", err)
+		snap.Rebuild(root)
+		return snap
+	}
+	// Existing snapshot loaded, seed all the layers
+	for head != nil {
+		snap.layers[head.Root()] = head
+		head = head.Parent()
+	}
+	return snap
+}
+
+// waitBuild blocks until the snapshot finishes rebuilding. This method is meant
+// to  be used by tests to ensure we're testing what we believe we are.
+func (t *Tree) waitBuild() {
+	// Find the rebuild termination channel
+	var done chan struct{}
+
+	t.lock.RLock()
+	for _, layer := range t.layers {
+		if layer, ok := layer.(*diskLayer); ok {
+			done = layer.genPending
+			break
+		}
+	}
+	t.lock.RUnlock()
+
+	// Wait until the snapshot is generated
+	if done != nil {
+		<-done
+	}
+}
+
+// Snapshot retrieves a snapshot belonging to the given block root, or nil if no
+// snapshot is maintained for that block.
+func (t *Tree) Snapshot(blockRoot common.Hash) Snapshot {
+	t.lock.RLock()
+	defer t.lock.RUnlock()
+
+	return t.layers[blockRoot]
+}
+
+// Update adds a new snapshot into the tree, if that can be linked to an existing
+// old parent. It is disallowed to insert a disk layer (the origin of all).
+func (t *Tree) Update(blockRoot common.Hash, parentRoot common.Hash, destructs map[common.Hash]struct{}, accounts map[common.Hash][]byte, storage map[common.Hash]map[common.Hash][]byte) error {
+	// Reject noop updates to avoid self-loops in the snapshot tree. This is a
+	// special case that can only happen for Clique networks where empty blocks
+	// don't modify the state (0 block subsidy).
+	//
+	// Although we could silently ignore this internally, it should be the caller's
+	// responsibility to avoid even attempting to insert such a snapshot.
+	if blockRoot == parentRoot {
+		return errSnapshotCycle
+	}
+	// Generate a new snapshot on top of the parent
+	parent := t.Snapshot(parentRoot).(snapshot)
+	if parent == nil {
+		return fmt.Errorf("parent [%#x] snapshot missing", parentRoot)
+	}
+	snap := parent.Update(blockRoot, destructs, accounts, storage)
+
+	// Save the new snapshot for later
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	t.layers[snap.root] = snap
+	return nil
+}
+
+// Cap traverses downwards the snapshot tree from a head block hash until the
+// number of allowed layers are crossed. All layers beyond the permitted number
+// are flattened downwards.
+func (t *Tree) Cap(root common.Hash, layers int) error {
+	// Retrieve the head snapshot to cap from
+	snap := t.Snapshot(root)
+	if snap == nil {
+		return fmt.Errorf("snapshot [%#x] missing", root)
+	}
+	diff, ok := snap.(*diffLayer)
+	if !ok {
+		return fmt.Errorf("snapshot [%#x] is disk layer", root)
+	}
+	// If the generator is still running, use a more aggressive cap
+	diff.origin.lock.RLock()
+	if diff.origin.genMarker != nil && layers > 8 {
+		layers = 8
+	}
+	diff.origin.lock.RUnlock()
+
+	// Run the internal capping and discard all stale layers
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	// Flattening the bottom-most diff layer requires special casing since there's
+	// no child to rewire to the grandparent. In that case we can fake a temporary
+	// child for the capping and then remove it.
+	var persisted *diskLayer
+
+	switch layers {
+	case 0:
+		// If full commit was requested, flatten the diffs and merge onto disk
+		diff.lock.RLock()
+		base := diffToDisk(diff.flatten().(*diffLayer))
+		diff.lock.RUnlock()
+
+		// Replace the entire snapshot tree with the flat base
+		t.layers = map[common.Hash]snapshot{base.root: base}
+		return nil
+
+	case 1:
+		// If full flattening was requested, flatten the diffs but only merge if the
+		// memory limit was reached
+		var (
+			bottom *diffLayer
+			base   *diskLayer
+		)
+		diff.lock.RLock()
+		bottom = diff.flatten().(*diffLayer)
+		if bottom.memory >= aggregatorMemoryLimit {
+			base = diffToDisk(bottom)
+		}
+		diff.lock.RUnlock()
+
+		// If all diff layers were removed, replace the entire snapshot tree
+		if base != nil {
+			t.layers = map[common.Hash]snapshot{base.root: base}
+			return nil
+		}
+		// Merge the new aggregated layer into the snapshot tree, clean stales below
+		t.layers[bottom.root] = bottom
+
+	default:
+		// Many layers requested to be retained, cap normally
+		persisted = t.cap(diff, layers)
+	}
+	// Remove any layer that is stale or links into a stale layer
+	children := make(map[common.Hash][]common.Hash)
+	for root, snap := range t.layers {
+		if diff, ok := snap.(*diffLayer); ok {
+			parent := diff.parent.Root()
+			children[parent] = append(children[parent], root)
+		}
+	}
+	var remove func(root common.Hash)
+	remove = func(root common.Hash) {
+		delete(t.layers, root)
+		for _, child := range children[root] {
+			remove(child)
+		}
+		delete(children, root)
+	}
+	for root, snap := range t.layers {
+		if snap.Stale() {
+			remove(root)
+		}
+	}
+	// If the disk layer was modified, regenerate all the cumulative blooms
+	if persisted != nil {
+		var rebloom func(root common.Hash)
+		rebloom = func(root common.Hash) {
+			if diff, ok := t.layers[root].(*diffLayer); ok {
+				diff.rebloom(persisted)
+			}
+			for _, child := range children[root] {
+				rebloom(child)
+			}
+		}
+		rebloom(persisted.root)
+	}
+	return nil
+}
+
+// cap traverses downwards the diff tree until the number of allowed layers are
+// crossed. All diffs beyond the permitted number are flattened downwards. If the
+// layer limit is reached, memory cap is also enforced (but not before).
+//
+// The method returns the new disk layer if diffs were persistend into it.
+func (t *Tree) cap(diff *diffLayer, layers int) *diskLayer {
+	// Dive until we run out of layers or reach the persistent database
+	for ; layers > 2; layers-- {
+		// If we still have diff layers below, continue down
+		if parent, ok := diff.parent.(*diffLayer); ok {
+			diff = parent
+		} else {
+			// Diff stack too shallow, return without modifications
+			return nil
+		}
+	}
+	// We're out of layers, flatten anything below, stopping if it's the disk or if
+	// the memory limit is not yet exceeded.
+	switch parent := diff.parent.(type) {
+	case *diskLayer:
+		return nil
+
+	case *diffLayer:
+		// Flatten the parent into the grandparent. The flattening internally obtains a
+		// write lock on grandparent.
+		flattened := parent.flatten().(*diffLayer)
+		t.layers[flattened.root] = flattened
+
+		diff.lock.Lock()
+		defer diff.lock.Unlock()
+
+		diff.parent = flattened
+		if flattened.memory < aggregatorMemoryLimit {
+			// Accumulator layer is smaller than the limit, so we can abort, unless
+			// there's a snapshot being generated currently. In that case, the trie
+			// will move fron underneath the generator so we **must** merge all the
+			// partial data down into the snapshot and restart the generation.
+			if flattened.parent.(*diskLayer).genAbort == nil {
+				return nil
+			}
+		}
+	default:
+		panic(fmt.Sprintf("unknown data layer: %T", parent))
+	}
+	// If the bottom-most layer is larger than our memory cap, persist to disk
+	bottom := diff.parent.(*diffLayer)
+
+	bottom.lock.RLock()
+	base := diffToDisk(bottom)
+	bottom.lock.RUnlock()
+
+	t.layers[base.root] = base
+	diff.parent = base
+	return base
+}
+
+// diffToDisk merges a bottom-most diff into the persistent disk layer underneath
+// it. The method will panic if called onto a non-bottom-most diff layer.
+func diffToDisk(bottom *diffLayer) *diskLayer {
+	var (
+		base  = bottom.parent.(*diskLayer)
+		batch = base.diskdb.NewBatch()
+		stats *generatorStats
+	)
+	// If the disk layer is running a snapshot generator, abort it
+	if base.genAbort != nil {
+		abort := make(chan *generatorStats)
+		base.genAbort <- abort
+		stats = <-abort
+	}
+	// Start by temporarily deleting the current snapshot block marker. This
+	// ensures that in the case of a crash, the entire snapshot is invalidated.
+	rawdb.DeleteSnapshotRoot(batch)
+
+	// Mark the original base as stale as we're going to create a new wrapper
+	base.lock.Lock()
+	if base.stale {
+		panic("parent disk layer is stale") // we've committed into the same base from two children, boo
+	}
+	base.stale = true
+	base.lock.Unlock()
+
+	// Destroy all the destructed accounts from the database
+	for hash := range bottom.destructSet {
+		// Skip any account not covered yet by the snapshot
+		if base.genMarker != nil && bytes.Compare(hash[:], base.genMarker) > 0 {
+			continue
+		}
+		// Remove all storage slots
+		rawdb.DeleteAccountSnapshot(batch, hash)
+		base.cache.Set(hash[:], nil)
+
+		it := rawdb.IterateStorageSnapshots(base.diskdb, hash)
+		for it.Next() {
+			if key := it.Key(); len(key) == 65 { // TODO(karalabe): Yuck, we should move this into the iterator
+				batch.Delete(key)
+				base.cache.Del(key[1:])
+
+				snapshotFlushStorageItemMeter.Mark(1)
+			}
+		}
+		it.Release()
+	}
+	// Push all updated accounts into the database
+	for hash, data := range bottom.accountData {
+		// Skip any account not covered yet by the snapshot
+		if base.genMarker != nil && bytes.Compare(hash[:], base.genMarker) > 0 {
+			continue
+		}
+		// Push the account to disk
+		rawdb.WriteAccountSnapshot(batch, hash, data)
+		base.cache.Set(hash[:], data)
+		snapshotCleanAccountWriteMeter.Mark(int64(len(data)))
+
+		if batch.ValueSize() > ethdb.IdealBatchSize {
+			if err := batch.Write(); err != nil {
+				log.Crit("Failed to write account snapshot", "err", err)
+			}
+			batch.Reset()
+		}
+		snapshotFlushAccountItemMeter.Mark(1)
+		snapshotFlushAccountSizeMeter.Mark(int64(len(data)))
+	}
+	// Push all the storage slots into the database
+	for accountHash, storage := range bottom.storageData {
+		// Skip any account not covered yet by the snapshot
+		if base.genMarker != nil && bytes.Compare(accountHash[:], base.genMarker) > 0 {
+			continue
+		}
+		// Generation might be mid-account, track that case too
+		midAccount := base.genMarker != nil && bytes.Equal(accountHash[:], base.genMarker[:common.HashLength])
+
+		for storageHash, data := range storage {
+			// Skip any slot not covered yet by the snapshot
+			if midAccount && bytes.Compare(storageHash[:], base.genMarker[common.HashLength:]) > 0 {
+				continue
+			}
+			if len(data) > 0 {
+				rawdb.WriteStorageSnapshot(batch, accountHash, storageHash, data)
+				base.cache.Set(append(accountHash[:], storageHash[:]...), data)
+				snapshotCleanStorageWriteMeter.Mark(int64(len(data)))
+			} else {
+				rawdb.DeleteStorageSnapshot(batch, accountHash, storageHash)
+				base.cache.Set(append(accountHash[:], storageHash[:]...), nil)
+			}
+			snapshotFlushStorageItemMeter.Mark(1)
+			snapshotFlushStorageSizeMeter.Mark(int64(len(data)))
+		}
+		if batch.ValueSize() > ethdb.IdealBatchSize {
+			if err := batch.Write(); err != nil {
+				log.Crit("Failed to write storage snapshot", "err", err)
+			}
+			batch.Reset()
+		}
+	}
+	// Update the snapshot block marker and write any remainder data
+	rawdb.WriteSnapshotRoot(batch, bottom.root)
+	if err := batch.Write(); err != nil {
+		log.Crit("Failed to write leftover snapshot", "err", err)
+	}
+	res := &diskLayer{
+		root:       bottom.root,
+		cache:      base.cache,
+		diskdb:     base.diskdb,
+		triedb:     base.triedb,
+		genMarker:  base.genMarker,
+		genPending: base.genPending,
+	}
+	// If snapshot generation hasn't finished yet, port over all the starts and
+	// continue where the previous round left off.
+	//
+	// Note, the `base.genAbort` comparison is not used normally, it's checked
+	// to allow the tests to play with the marker without triggering this path.
+	if base.genMarker != nil && base.genAbort != nil {
+		res.genMarker = base.genMarker
+		res.genAbort = make(chan chan *generatorStats)
+		go res.generate(stats)
+	}
+	return res
+}
+
+// Journal commits an entire diff hierarchy to disk into a single journal entry.
+// This is meant to be used during shutdown to persist the snapshot without
+// flattening everything down (bad for reorgs).
+//
+// The method returns the root hash of the base layer that needs to be persisted
+// to disk as a trie too to allow continuing any pending generation op.
+func (t *Tree) Journal(root common.Hash) (common.Hash, error) {
+	// Retrieve the head snapshot to journal from var snap snapshot
+	snap := t.Snapshot(root)
+	if snap == nil {
+		return common.Hash{}, fmt.Errorf("snapshot [%#x] missing", root)
+	}
+	// Run the journaling
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	journal := new(bytes.Buffer)
+	base, err := snap.(snapshot).Journal(journal)
+	if err != nil {
+		return common.Hash{}, err
+	}
+	// Store the journal into the database and return
+	rawdb.WriteSnapshotJournal(t.diskdb, journal.Bytes())
+	return base, nil
+}
+
+// Rebuild wipes all available snapshot data from the persistent database and
+// discard all caches and diff layers. Afterwards, it starts a new snapshot
+// generator with the given root hash.
+func (t *Tree) Rebuild(root common.Hash) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	// Track whether there's a wipe currently running and keep it alive if so
+	var wiper chan struct{}
+
+	// Iterate over and mark all layers stale
+	for _, layer := range t.layers {
+		switch layer := layer.(type) {
+		case *diskLayer:
+			// If the base layer is generating, abort it and save
+			if layer.genAbort != nil {
+				abort := make(chan *generatorStats)
+				layer.genAbort <- abort
+
+				if stats := <-abort; stats != nil {
+					wiper = stats.wiping
+				}
+			}
+			// Layer should be inactive now, mark it as stale
+			layer.lock.Lock()
+			layer.stale = true
+			layer.lock.Unlock()
+
+		case *diffLayer:
+			// If the layer is a simple diff, simply mark as stale
+			layer.lock.Lock()
+			atomic.StoreUint32(&layer.stale, 1)
+			layer.lock.Unlock()
+
+		default:
+			panic(fmt.Sprintf("unknown layer type: %T", layer))
+		}
+	}
+	// Start generating a new snapshot from scratch on a backgroung thread. The
+	// generator will run a wiper first if there's not one running right now.
+	log.Info("Rebuilding state snapshot")
+	t.layers = map[common.Hash]snapshot{
+		root: generateSnapshot(t.diskdb, t.triedb, t.cache, root, wiper),
+	}
+}
+
+// AccountIterator creates a new account iterator for the specified root hash and
+// seeks to a starting account hash.
+func (t *Tree) AccountIterator(root common.Hash, seek common.Hash) (AccountIterator, error) {
+	return newFastAccountIterator(t, root, seek)
+}
+
+// StorageIterator creates a new storage iterator for the specified root hash and
+// account. The iterator will be move to the specific start position.
+func (t *Tree) StorageIterator(root common.Hash, account common.Hash, seek common.Hash) (StorageIterator, error) {
+	return newFastStorageIterator(t, root, account, seek)
+}