trie: added error handling

Created alternate versions of Trie and SecureTrie functions that can return a MissingNodeError (used by ODR services)

trie/arc.go

@@ -62,6 +62,18 @@ func newARC(c int) *arc {
 	}
 }
 
+// Clear clears the cache
+func (a *arc) Clear() {
+	a.mutex.Lock()
+	defer a.mutex.Unlock()
+	a.p = 0
+	a.t1 = list.New()
+	a.b1 = list.New()
+	a.t2 = list.New()
+	a.b2 = list.New()
+	a.cache = make(map[string]*entry, a.c)
+}
+
 // Put inserts a new key-value pair into the cache.
 // This optimizes future access to this entry (side effect).
 func (a *arc) Put(key hashNode, value node) bool {

trie/errors.go

@@ -0,0 +1,41 @@
+// Copyright 2014 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 trie
+
+import (
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+// MissingNodeError is returned by the trie functions (TryGet, TryUpdate, TryDelete)
+// in the case where a trie node is not present in the local database. Contains
+// information necessary for retrieving the missing node through an ODR service.
+//
+// NodeHash is the hash of the missing node
+// RootHash is the original root of the trie that contains the node
+// KeyPrefix is the prefix that leads from the root to the missing node (hex encoded)
+// KeySuffix (optional) contains the rest of the key we were looking for, gives a
+//  hint on which further nodes should also be retrieved (hex encoded)
+type MissingNodeError struct {
+	RootHash, NodeHash   common.Hash
+	KeyPrefix, KeySuffix []byte
+}
+
+func (err *MissingNodeError) Error() string {
+	return fmt.Sprintf("Missing trie node %064x", err.NodeHash)
+}

trie/iterator.go

@@ -16,7 +16,12 @@
 
 package trie
 
-import "bytes"
+import (
+	"bytes"
+
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
+)
 
 type Iterator struct {
 	trie *Trie
@@ -100,7 +105,11 @@ func (self *Iterator) next(node interface{}, key []byte, isIterStart bool) []byt
 		}
 
 	case hashNode:
-		return self.next(self.trie.resolveHash(node), key, isIterStart)
+		rn, err := self.trie.resolveHash(node, nil, nil)
+		if err != nil && glog.V(logger.Error) {
+			glog.Errorf("Unhandled trie error: %v", err)
+		}
+		return self.next(rn, key, isIterStart)
 	}
 	return nil
 }
@@ -127,7 +136,11 @@ func (self *Iterator) key(node interface{}) []byte {
 			}
 		}
 	case hashNode:
-		return self.key(self.trie.resolveHash(node))
+		rn, err := self.trie.resolveHash(node, nil, nil)
+		if err != nil && glog.V(logger.Error) {
+			glog.Errorf("Unhandled trie error: %v", err)
+		}
+		return self.key(rn)
 	}
 
 	return nil

trie/proof.go

@@ -7,6 +7,8 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto/sha3"
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
 	"github.com/ethereum/go-ethereum/rlp"
 )
 
@@ -39,7 +41,14 @@ func (t *Trie) Prove(key []byte) []rlp.RawValue {
 		case nil:
 			return nil
 		case hashNode:
-			tn = t.resolveHash(n)
+			var err error
+			tn, err = t.resolveHash(n, nil, nil)
+			if err != nil {
+				if glog.V(logger.Error) {
+					glog.Errorf("Unhandled trie error: %v", err)
+				}
+				return nil
+			}
 		default:
 			panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
 		}

trie/secure_trie.go

@@ -21,6 +21,8 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto/sha3"
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
 )
 
 var secureKeyPrefix = []byte("secure-key-")
@@ -46,8 +48,8 @@ type SecureTrie struct {
 // NewSecure creates a trie with an existing root node from db.
 //
 // If root is the zero hash or the sha3 hash of an empty string, the
-// trie is initially empty. Otherwise, New will panics if db is nil
-// and returns ErrMissingRoot if the root node cannpt be found.
+// trie is initially empty. Otherwise, New will panic if db is nil
+// and returns MissingNodeError if the root node cannot be found.
 // Accessing the trie loads nodes from db on demand.
 func NewSecure(root common.Hash, db Database) (*SecureTrie, error) {
 	if db == nil {
@@ -63,7 +65,18 @@ func NewSecure(root common.Hash, db Database) (*SecureTrie, error) {
 // Get returns the value for key stored in the trie.
 // The value bytes must not be modified by the caller.
 func (t *SecureTrie) Get(key []byte) []byte {
-	return t.Trie.Get(t.hashKey(key))
+	res, err := t.TryGet(key)
+	if err != nil && glog.V(logger.Error) {
+		glog.Errorf("Unhandled trie error: %v", err)
+	}
+	return res
+}
+
+// TryGet returns the value for key stored in the trie.
+// The value bytes must not be modified by the caller.
+// If a node was not found in the database, a MissingNodeError is returned.
+func (t *SecureTrie) TryGet(key []byte) ([]byte, error) {
+	return t.Trie.TryGet(t.hashKey(key))
 }
 
 // Update associates key with value in the trie. Subsequent calls to
@@ -73,14 +86,40 @@ func (t *SecureTrie) Get(key []byte) []byte {
 // The value bytes must not be modified by the caller while they are
 // stored in the trie.
 func (t *SecureTrie) Update(key, value []byte) {
+	if err := t.TryUpdate(key, value); err != nil && glog.V(logger.Error) {
+		glog.Errorf("Unhandled trie error: %v", err)
+	}
+}
+
+// TryUpdate associates key with value in the trie. Subsequent calls to
+// Get will return value. If value has length zero, any existing value
+// is deleted from the trie and calls to Get will return nil.
+//
+// The value bytes must not be modified by the caller while they are
+// stored in the trie.
+//
+// If a node was not found in the database, a MissingNodeError is returned.
+func (t *SecureTrie) TryUpdate(key, value []byte) error {
 	hk := t.hashKey(key)
-	t.Trie.Update(hk, value)
+	err := t.Trie.TryUpdate(hk, value)
+	if err != nil {
+		return err
+	}
 	t.Trie.db.Put(t.secKey(hk), key)
+	return nil
 }
 
 // Delete removes any existing value for key from the trie.
 func (t *SecureTrie) Delete(key []byte) {
-	t.Trie.Delete(t.hashKey(key))
+	if err := t.TryDelete(key); err != nil && glog.V(logger.Error) {
+		glog.Errorf("Unhandled trie error: %v", err)
+	}
+}
+
+// TryDelete removes any existing value for key from the trie.
+// If a node was not found in the database, a MissingNodeError is returned.
+func (t *SecureTrie) TryDelete(key []byte) error {
+	return t.Trie.TryDelete(t.hashKey(key))
 }
 
 // GetKey returns the sha3 preimage of a hashed key that was

trie/trie.go

@@ -19,7 +19,6 @@ package trie
 
 import (
 	"bytes"
-	"errors"
 	"fmt"
 	"hash"
 
@@ -44,7 +43,10 @@ var (
 	emptyState = crypto.Sha3Hash(nil)
 )
 
-var ErrMissingRoot = errors.New("missing root node")
+// ClearGlobalCache clears the global trie cache
+func ClearGlobalCache() {
+	globalCache.Clear()
+}
 
 // Database must be implemented by backing stores for the trie.
 type Database interface {
@@ -69,6 +71,7 @@ type DatabaseWriter interface {
 type Trie struct {
 	root         node
 	db           Database
+	originalRoot common.Hash
 	*hasher
 }
 
@@ -76,16 +79,19 @@ type Trie struct {
 //
 // If root is the zero hash or the sha3 hash of an empty string, the
 // trie is initially empty and does not require a database. Otherwise,
-// New will panics if db is nil or root does not exist in the
-// database. Accessing the trie loads nodes from db on demand.
+// New will panic if db is nil and returns a MissingNodeError if root does
+// not exist in the database. Accessing the trie loads nodes from db on demand.
 func New(root common.Hash, db Database) (*Trie, error) {
-	trie := &Trie{db: db}
+	trie := &Trie{db: db, originalRoot: root}
 	if (root != common.Hash{}) && root != emptyRoot {
 		if db == nil {
 			panic("trie.New: cannot use existing root without a database")
 		}
 		if v, _ := trie.db.Get(root[:]); len(v) == 0 {
-			return nil, ErrMissingRoot
+			return nil, &MissingNodeError{
+				RootHash: root,
+				NodeHash: root,
+			}
 		}
 		trie.root = hashNode(root.Bytes())
 	}
@@ -100,28 +106,44 @@ func (t *Trie) Iterator() *Iterator {
 // Get returns the value for key stored in the trie.
 // The value bytes must not be modified by the caller.
 func (t *Trie) Get(key []byte) []byte {
+	res, err := t.TryGet(key)
+	if err != nil && glog.V(logger.Error) {
+		glog.Errorf("Unhandled trie error: %v", err)
+	}
+	return res
+}
+
+// TryGet returns the value for key stored in the trie.
+// The value bytes must not be modified by the caller.
+// If a node was not found in the database, a MissingNodeError is returned.
+func (t *Trie) TryGet(key []byte) ([]byte, error) {
 	key = compactHexDecode(key)
+	pos := 0
 	tn := t.root
-	for len(key) > 0 {
+	for pos < len(key) {
 		switch n := tn.(type) {
 		case shortNode:
-			if len(key) < len(n.Key) || !bytes.Equal(n.Key, key[:len(n.Key)]) {
-				return nil
+			if len(key)-pos < len(n.Key) || !bytes.Equal(n.Key, key[pos:pos+len(n.Key)]) {
+				return nil, nil
 			}
 			tn = n.Val
-			key = key[len(n.Key):]
+			pos += len(n.Key)
 		case fullNode:
-			tn = n[key[0]]
-			key = key[1:]
+			tn = n[key[pos]]
+			pos++
 		case nil:
-			return nil
+			return nil, nil
 		case hashNode:
-			tn = t.resolveHash(n)
+			var err error
+			tn, err = t.resolveHash(n, key[:pos], key[pos:])
+			if err != nil {
+				return nil, err
+			}
 		default:
 			panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
 		}
 	}
-	return tn.(valueNode)
+	return tn.(valueNode), nil
 }
 
 // Update associates key with value in the trie. Subsequent calls to
@@ -131,17 +153,40 @@ func (t *Trie) Get(key []byte) []byte {
 // The value bytes must not be modified by the caller while they are
 // stored in the trie.
 func (t *Trie) Update(key, value []byte) {
+	if err := t.TryUpdate(key, value); err != nil && glog.V(logger.Error) {
+		glog.Errorf("Unhandled trie error: %v", err)
+	}
+}
+
+// TryUpdate associates key with value in the trie. Subsequent calls to
+// Get will return value. If value has length zero, any existing value
+// is deleted from the trie and calls to Get will return nil.
+//
+// The value bytes must not be modified by the caller while they are
+// stored in the trie.
+//
+// If a node was not found in the database, a MissingNodeError is returned.
+func (t *Trie) TryUpdate(key, value []byte) error {
 	k := compactHexDecode(key)
 	if len(value) != 0 {
-		t.root = t.insert(t.root, k, valueNode(value))
+		n, err := t.insert(t.root, nil, k, valueNode(value))
+		if err != nil {
+			return err
+		}
+		t.root = n
 	} else {
-		t.root = t.delete(t.root, k)
+		n, err := t.delete(t.root, nil, k)
+		if err != nil {
+			return err
 		}
+		t.root = n
+	}
+	return nil
 }
 
-func (t *Trie) insert(n node, key []byte, value node) node {
+func (t *Trie) insert(n node, prefix, key []byte, value node) (node, error) {
 	if len(key) == 0 {
-		return value
+		return value, nil
 	}
 	switch n := n.(type) {
 	case shortNode:
@@ -149,25 +194,40 @@ func (t *Trie) insert(n node, key []byte, value node) node {
 		// If the whole key matches, keep this short node as is
 		// and only update the value.
 		if matchlen == len(n.Key) {
-			return shortNode{n.Key, t.insert(n.Val, key[matchlen:], value)}
+			nn, err := t.insert(n.Val, append(prefix, key[:matchlen]...), key[matchlen:], value)
+			if err != nil {
+				return nil, err
+			}
+			return shortNode{n.Key, nn}, nil
 		}
 		// Otherwise branch out at the index where they differ.
 		var branch fullNode
-		branch[n.Key[matchlen]] = t.insert(nil, n.Key[matchlen+1:], n.Val)
-		branch[key[matchlen]] = t.insert(nil, key[matchlen+1:], value)
+		var err error
+		branch[n.Key[matchlen]], err = t.insert(nil, append(prefix, n.Key[:matchlen+1]...), n.Key[matchlen+1:], n.Val)
+		if err != nil {
+			return nil, err
+		}
+		branch[key[matchlen]], err = t.insert(nil, append(prefix, key[:matchlen+1]...), key[matchlen+1:], value)
+		if err != nil {
+			return nil, err
+		}
 		// Replace this shortNode with the branch if it occurs at index 0.
 		if matchlen == 0 {
-			return branch
+			return branch, nil
 		}
 		// Otherwise, replace it with a short node leading up to the branch.
-		return shortNode{key[:matchlen], branch}
+		return shortNode{key[:matchlen], branch}, nil
 
 	case fullNode:
-		n[key[0]] = t.insert(n[key[0]], key[1:], value)
-		return n
+		nn, err := t.insert(n[key[0]], append(prefix, key[0]), key[1:], value)
+		if err != nil {
+			return nil, err
+		}
+		n[key[0]] = nn
+		return n, nil
 
 	case nil:
-		return shortNode{key, value}
+		return shortNode{key, value}, nil
 
 	case hashNode:
 		// We've hit a part of the trie that isn't loaded yet. Load
@@ -176,7 +236,11 @@ func (t *Trie) insert(n node, key []byte, value node) node {
 		//
 		// TODO: track whether insertion changed the value and keep
 		// n as a hash node if it didn't.
-		return t.insert(t.resolveHash(n), key, value)
+		rn, err := t.resolveHash(n, prefix, key)
+		if err != nil {
+			return nil, err
+		}
+		return t.insert(rn, prefix, key, value)
 
 	default:
 		panic(fmt.Sprintf("%T: invalid node: %v", n, n))
@@ -185,28 +249,44 @@ func (t *Trie) insert(n node, key []byte, value node) node {
 
 // Delete removes any existing value for key from the trie.
 func (t *Trie) Delete(key []byte) {
+	if err := t.TryDelete(key); err != nil && glog.V(logger.Error) {
+		glog.Errorf("Unhandled trie error: %v", err)
+	}
+}
+
+// TryDelete removes any existing value for key from the trie.
+// If a node was not found in the database, a MissingNodeError is returned.
+func (t *Trie) TryDelete(key []byte) error {
 	k := compactHexDecode(key)
-	t.root = t.delete(t.root, k)
+	n, err := t.delete(t.root, nil, k)
+	if err != nil {
+		return err
+	}
+	t.root = n
+	return nil
 }
 
 // delete returns the new root of the trie with key deleted.
 // It reduces the trie to minimal form by simplifying
 // nodes on the way up after deleting recursively.
-func (t *Trie) delete(n node, key []byte) node {
+func (t *Trie) delete(n node, prefix, key []byte) (node, error) {
 	switch n := n.(type) {
 	case shortNode:
 		matchlen := prefixLen(key, n.Key)
 		if matchlen < len(n.Key) {
-			return n // don't replace n on mismatch
+			return n, nil // don't replace n on mismatch
 		}
 		if matchlen == len(key) {
-			return nil // remove n entirely for whole matches
+			return nil, nil // remove n entirely for whole matches
 		}
 		// The key is longer than n.Key. Remove the remaining suffix
 		// from the subtrie. Child can never be nil here since the
 		// subtrie must contain at least two other values with keys
 		// longer than n.Key.
-		child := t.delete(n.Val, key[len(n.Key):])
+		child, err := t.delete(n.Val, append(prefix, key[:len(n.Key)]...), key[len(n.Key):])
+		if err != nil {
+			return nil, err
+		}
 		switch child := child.(type) {
 		case shortNode:
 			// Deleting from the subtrie reduced it to another
@@ -215,13 +295,17 @@ func (t *Trie) delete(n node, key []byte) node {
 			// always creates a new slice) instead of append to
 			// avoid modifying n.Key since it might be shared with
 			// other nodes.
-			return shortNode{concat(n.Key, child.Key...), child.Val}
+			return shortNode{concat(n.Key, child.Key...), child.Val}, nil
 		default:
-			return shortNode{n.Key, child}
+			return shortNode{n.Key, child}, nil
 		}
 
 	case fullNode:
-		n[key[0]] = t.delete(n[key[0]], key[1:])
+		nn, err := t.delete(n[key[0]], append(prefix, key[0]), key[1:])
+		if err != nil {
+			return nil, err
+		}
+		n[key[0]] = nn
 		// Check how many non-nil entries are left after deleting and
 		// reduce the full node to a short node if only one entry is
 		// left. Since n must've contained at least two children
@@ -250,21 +334,24 @@ func (t *Trie) delete(n node, key []byte) node {
 				// shortNode{..., shortNode{...}}.  Since the entry
 				// might not be loaded yet, resolve it just for this
 				// check.
-				cnode := t.resolve(n[pos])
+				cnode, err := t.resolve(n[pos], prefix, []byte{byte(pos)})
+				if err != nil {
+					return nil, err
+				}
 				if cnode, ok := cnode.(shortNode); ok {
 					k := append([]byte{byte(pos)}, cnode.Key...)
-					return shortNode{k, cnode.Val}
+					return shortNode{k, cnode.Val}, nil
 				}
 			}
 			// Otherwise, n is replaced by a one-nibble short node
 			// containing the child.
-			return shortNode{[]byte{byte(pos)}, n[pos]}
+			return shortNode{[]byte{byte(pos)}, n[pos]}, nil
 		}
 		// n still contains at least two values and cannot be reduced.
-		return n
+		return n, nil
 
 	case nil:
-		return nil
+		return nil, nil
 
 	case hashNode:
 		// We've hit a part of the trie that isn't loaded yet. Load
@@ -273,7 +360,11 @@ func (t *Trie) delete(n node, key []byte) node {
 		//
 		// TODO: track whether deletion actually hit a key and keep
 		// n as a hash node if it didn't.
-		return t.delete(t.resolveHash(n), key)
+		rn, err := t.resolveHash(n, prefix, key)
+		if err != nil {
+			return nil, err
+		}
+		return t.delete(rn, prefix, key)
 
 	default:
 		panic(fmt.Sprintf("%T: invalid node: %v (%v)", n, n, key))
@@ -287,34 +378,31 @@ func concat(s1 []byte, s2 ...byte) []byte {
 	return r
 }
 
-func (t *Trie) resolve(n node) node {
+func (t *Trie) resolve(n node, prefix, suffix []byte) (node, error) {
 	if n, ok := n.(hashNode); ok {
-		return t.resolveHash(n)
+		return t.resolveHash(n, prefix, suffix)
 	}
-	return n
+	return n, nil
 }
 
-func (t *Trie) resolveHash(n hashNode) node {
+func (t *Trie) resolveHash(n hashNode, prefix, suffix []byte) (node, error) {
 	if v, ok := globalCache.Get(n); ok {
-		return v
+		return v, nil
 	}
 	enc, err := t.db.Get(n)
 	if err != nil || enc == nil {
-		// TODO: This needs to be improved to properly distinguish errors.
-		// Disk I/O errors shouldn't produce nil (and cause a
-		// consensus failure or weird crash), but it is unclear how
-		// they could be handled because the entire stack above the trie isn't
-		// prepared to cope with missing state nodes.
-		if glog.V(logger.Error) {
-			glog.Errorf("Dangling hash node ref %x: %v", n, err)
+		return nil, &MissingNodeError{
+			RootHash:  t.originalRoot,
+			NodeHash:  common.BytesToHash(n),
+			KeyPrefix: prefix,
+			KeySuffix: suffix,
 		}
-		return nil
 	}
 	dec := mustDecodeNode(n, enc)
 	if dec != nil {
 		globalCache.Put(n, dec)
 	}
-	return dec
+	return dec, nil
 }
 
 // Root returns the root hash of the trie.

trie/trie_test.go

@@ -64,11 +64,84 @@ func TestMissingRoot(t *testing.T) {
 	if trie != nil {
 		t.Error("New returned non-nil trie for invalid root")
 	}
-	if err != ErrMissingRoot {
+	if _, ok := err.(*MissingNodeError); !ok {
 		t.Error("New returned wrong error: %v", err)
 	}
 }
 
+func TestMissingNode(t *testing.T) {
+	db, _ := ethdb.NewMemDatabase()
+	trie, _ := New(common.Hash{}, db)
+	updateString(trie, "120000", "qwerqwerqwerqwerqwerqwerqwerqwer")
+	updateString(trie, "123456", "asdfasdfasdfasdfasdfasdfasdfasdf")
+	root, _ := trie.Commit()
+
+	ClearGlobalCache()
+
+	trie, _ = New(root, db)
+	_, err := trie.TryGet([]byte("120000"))
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	trie, _ = New(root, db)
+	_, err = trie.TryGet([]byte("120099"))
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	trie, _ = New(root, db)
+	_, err = trie.TryGet([]byte("123456"))
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	trie, _ = New(root, db)
+	err = trie.TryUpdate([]byte("120099"), []byte("zxcvzxcvzxcvzxcvzxcvzxcvzxcvzxcv"))
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	trie, _ = New(root, db)
+	err = trie.TryDelete([]byte("123456"))
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	db.Delete(common.FromHex("e1d943cc8f061a0c0b98162830b970395ac9315654824bf21b73b891365262f9"))
+	ClearGlobalCache()
+
+	trie, _ = New(root, db)
+	_, err = trie.TryGet([]byte("120000"))
+	if _, ok := err.(*MissingNodeError); !ok {
+		t.Errorf("Wrong error: %v", err)
+	}
+
+	trie, _ = New(root, db)
+	_, err = trie.TryGet([]byte("120099"))
+	if _, ok := err.(*MissingNodeError); !ok {
+		t.Errorf("Wrong error: %v", err)
+	}
+
+	trie, _ = New(root, db)
+	_, err = trie.TryGet([]byte("123456"))
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	trie, _ = New(root, db)
+	err = trie.TryUpdate([]byte("120099"), []byte("zxcv"))
+	if _, ok := err.(*MissingNodeError); !ok {
+		t.Errorf("Wrong error: %v", err)
+	}
+
+	trie, _ = New(root, db)
+	err = trie.TryDelete([]byte("123456"))
+	if _, ok := err.(*MissingNodeError); !ok {
+		t.Errorf("Wrong error: %v", err)
+	}
+}
+
 func TestInsert(t *testing.T) {
 	trie := newEmpty()