core/state, trie: add node iterator, test state/trie sync consistency

2 files changed, 237 insertions, 3 deletions

diff --git a/core/state/iterator.go b/core/state/iterator.go
new file mode 100644
index 000000000..a0b71f3ee
--- /dev/null
+++ b/core/state/iterator.go
@@ -0,0 +1,133 @@
+// Copyright 2015 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 state
+
+import (
+	"bytes"
+	"fmt"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/ethereum/go-ethereum/trie"
+)
+
+// NodeIterator is an iterator to traverse the entire state trie post-order,
+// including all of the contract code and contract state tries.
+type NodeIterator struct {
+	state *StateDB // State being iterated
+
+	stateIt *trie.NodeIterator // Primary iterator for the global state trie
+	dataIt  *trie.NodeIterator // Secondary iterator for the data trie of a contract
+	code    []byte             // Source code associated with a contract
+
+	Entry interface{} // Current state entry being iterated (internal representation)
+}
+
+// NewNodeIterator creates an post-order state node iterator.
+func NewNodeIterator(state *StateDB) *NodeIterator {
+	return &NodeIterator{
+		state: state,
+	}
+}
+
+// Next moves the iterator to the next node, returning whether there are any
+// further nodes.
+func (it *NodeIterator) Next() bool {
+	it.step()
+	return it.retrieve()
+}
+
+// step moves the iterator to the next entry of the state trie.
+func (it *NodeIterator) step() {
+	// Abort if we reached the end of the iteration
+	if it.state == nil {
+		return
+	}
+	// Initialize the iterator if we've just started
+	if it.stateIt == nil {
+		it.stateIt = trie.NewNodeIterator(it.state.trie.Trie)
+	}
+	// If we had data nodes previously, we surely have at least state nodes
+	if it.dataIt != nil {
+		if cont := it.dataIt.Next(); !cont {
+			it.dataIt = nil
+		}
+		return
+	}
+	// If we had source code previously, discard that
+	if it.code != nil {
+		it.code = nil
+		return
+	}
+	// Step to the next state trie node, terminating if we're out of nodes
+	if cont := it.stateIt.Next(); !cont {
+		it.state, it.stateIt = nil, nil
+		return
+	}
+	// If the state trie node is an internal entry, leave as is
+	if !it.stateIt.Leaf {
+		return
+	}
+	// Otherwise we've reached an account node, initiate data iteration
+	var account struct {
+		Nonce    uint64
+		Balance  *big.Int
+		Root     common.Hash
+		CodeHash []byte
+	}
+	err := rlp.Decode(bytes.NewReader(it.stateIt.LeafBlob), &account)
+	if err != nil {
+		panic(err)
+	}
+	dataTrie, err := trie.New(account.Root, it.state.db)
+	if err != nil {
+		panic(err)
+	}
+	it.dataIt = trie.NewNodeIterator(dataTrie)
+	if !it.dataIt.Next() {
+		it.dataIt = nil
+	}
+	if bytes.Compare(account.CodeHash, emptyCodeHash) != 0 {
+		it.code, err = it.state.db.Get(account.CodeHash)
+		if err != nil {
+			panic(fmt.Sprintf("code %x: %v", account.CodeHash, err))
+		}
+	}
+}
+
+// retrieve pulls and caches the current state entry the iterator is traversing.
+// The method returns whether there are any more data left for inspection.
+func (it *NodeIterator) retrieve() bool {
+	// Clear out any previously set values
+	it.Entry = nil
+
+	// If the iteration's done, return no available data
+	if it.state == nil {
+		return false
+	}
+	// Otherwise retrieve the current entry
+	switch {
+	case it.dataIt != nil:
+		it.Entry = it.dataIt.Node
+	case it.code != nil:
+		it.Entry = it.code
+	case it.stateIt != nil:
+		it.Entry = it.stateIt.Node
+	}
+	return true
+}
diff --git a/core/state/sync_test.go b/core/state/sync_test.go
index 0dab372ba..5d6d90d5d 100644
--- a/core/state/sync_test.go
+++ b/core/state/sync_test.go
@@ -18,10 +18,12 @@ package state
 
 import (
 	"bytes"
+	"fmt"
 	"math/big"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/trie"
 )
@@ -42,7 +44,7 @@ func makeTestState() (ethdb.Database, common.Hash, []*testAccount) {
 
 	// Fill it with some arbitrary data
 	accounts := []*testAccount{}
-	for i := byte(0); i < 255; i++ {
+	for i := byte(0); i < 96; i++ {
 		obj := state.GetOrNewStateObject(common.BytesToAddress([]byte{i}))
 		acc := &testAccount{address: common.BytesToAddress([]byte{i})}
 
@@ -61,6 +63,9 @@ func makeTestState() (ethdb.Database, common.Hash, []*testAccount) {
 	}
 	root, _ := state.Commit()
 
+	// Remove any potentially cached data from the test state creation
+	trie.ClearGlobalCache()
+
 	// Return the generated state
 	return db, root, accounts
 }
@@ -68,9 +73,18 @@ func makeTestState() (ethdb.Database, common.Hash, []*testAccount) {
 // checkStateAccounts cross references a reconstructed state with an expected
 // account array.
 func checkStateAccounts(t *testing.T, db ethdb.Database, root common.Hash, accounts []*testAccount) {
-	state, _ := New(root, db)
-	for i, acc := range accounts {
+	// Remove any potentially cached data from the state synchronisation
+	trie.ClearGlobalCache()
 
+	// Check root availability and state contents
+	state, err := New(root, db)
+	if err != nil {
+		t.Fatalf("failed to create state trie at %x: %v", root, err)
+	}
+	if err := checkStateConsistency(db, root); err != nil {
+		t.Fatalf("inconsistent state trie at %x: %v", root, err)
+	}
+	for i, acc := range accounts {
 		if balance := state.GetBalance(acc.address); balance.Cmp(acc.balance) != 0 {
 			t.Errorf("account %d: balance mismatch: have %v, want %v", i, balance, acc.balance)
 		}
@@ -83,6 +97,31 @@ func checkStateAccounts(t *testing.T, db ethdb.Database, root common.Hash, accou
 	}
 }
 
+// checkStateConsistency checks that all nodes in a state trie and indeed present.
+func checkStateConsistency(db ethdb.Database, root common.Hash) (failure error) {
+	// Capture any panics by the iterator
+	defer func() {
+		if r := recover(); r != nil {
+			failure = fmt.Errorf("%v", r)
+		}
+	}()
+	// Remove any potentially cached data from the test state creation or previous checks
+	trie.ClearGlobalCache()
+
+	// Create and iterate a state trie rooted in a sub-node
+	if _, err := db.Get(root.Bytes()); err != nil {
+		return
+	}
+	state, err := New(root, db)
+	if err != nil {
+		return
+	}
+	it := NewNodeIterator(state)
+	for it.Next() {
+	}
+	return nil
+}
+
 // Tests that an empty state is not scheduled for syncing.
 func TestEmptyStateSync(t *testing.T) {
 	empty := common.HexToHash("56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421")
@@ -236,3 +275,65 @@ func TestIterativeRandomDelayedStateSync(t *testing.T) {
 	// Cross check that the two states are in sync
 	checkStateAccounts(t, dstDb, srcRoot, srcAccounts)
 }
+
+// Tests that at any point in time during a sync, only complete sub-tries are in
+// the database.
+func TestIncompleteStateSync(t *testing.T) {
+	// Create a random state to copy
+	srcDb, srcRoot, srcAccounts := makeTestState()
+
+	// Create a destination state and sync with the scheduler
+	dstDb, _ := ethdb.NewMemDatabase()
+	sched := NewStateSync(srcRoot, dstDb)
+
+	added := []common.Hash{}
+	queue := append([]common.Hash{}, sched.Missing(1)...)
+	for len(queue) > 0 {
+		// Fetch a batch of state nodes
+		results := make([]trie.SyncResult, len(queue))
+		for i, hash := range queue {
+			data, err := srcDb.Get(hash.Bytes())
+			if err != nil {
+				t.Fatalf("failed to retrieve node data for %x: %v", hash, err)
+			}
+			results[i] = trie.SyncResult{hash, data}
+		}
+		// Process each of the state nodes
+		if index, err := sched.Process(results); err != nil {
+			t.Fatalf("failed to process result #%d: %v", index, err)
+		}
+		for _, result := range results {
+			added = append(added, result.Hash)
+		}
+		// Check that all known sub-tries in the synced state is complete
+		for _, root := range added {
+			// Skim through the accounts and make sure the root hash is not a code node
+			codeHash := false
+			for _, acc := range srcAccounts {
+				if bytes.Compare(root.Bytes(), crypto.Sha3(acc.code)) == 0 {
+					codeHash = true
+					break
+				}
+			}
+			// If the root is a real trie node, check consistency
+			if !codeHash {
+				if err := checkStateConsistency(dstDb, root); err != nil {
+					t.Fatalf("state inconsistent: %v", err)
+				}
+			}
+		}
+		// Fetch the next batch to retrieve
+		queue = append(queue[:0], sched.Missing(1)...)
+	}
+	// Sanity check that removing any node from the database is detected
+	for _, node := range added[1:] {
+		key := node.Bytes()
+		value, _ := dstDb.Get(key)
+
+		dstDb.Delete(key)
+		if err := checkStateConsistency(dstDb, added[0]); err == nil {
+			t.Fatalf("trie inconsistency not caught, missing: %x", key)
+		}
+		dstDb.Put(key, value)
+	}
+}