trie: added error handling

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

1 files changed, 146 insertions, 58 deletions

diff --git a/trie/trie.go b/trie/trie.go
index a3a383fb5..717296e27 100644
--- a/trie/trie.go
+++ b/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 {
@@ -67,8 +69,9 @@ type DatabaseWriter interface {
 //
 // Trie is not safe for concurrent use.
 type Trie struct {
-	root node
-	db   Database
+	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.