// 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 trie
import (
"errors"
"fmt"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/ethdb"
"gopkg.in/karalabe/cookiejar.v2/collections/prque"
)
// ErrNotRequested is returned by the trie sync when it's requested to process a
// node it did not request.
var ErrNotRequested = errors.New("not requested")
// request represents a scheduled or already in-flight state retrieval request.
type request struct {
hash common.Hash // Hash of the node data content to retrieve
data []byte // Data content of the node, cached until all subtrees complete
object *node // Target node to populate with retrieved data (hashnode originally)
parents []*request // Parent state nodes referencing this entry (notify all upon completion)
depth int // Depth level within the trie the node is located to prioritise DFS
deps int // Number of dependencies before allowed to commit this node
callback TrieSyncLeafCallback // Callback to invoke if a leaf node it reached on this branch
}
// SyncResult is a simple list to return missing nodes along with their request
// hashes.
type SyncResult struct {
Hash common.Hash // Hash of the originally unknown trie node
Data []byte // Data content of the retrieved node
}
// TrieSyncLeafCallback is a callback type invoked when a trie sync reaches a
// leaf node. It's used by state syncing to check if the leaf node requires some
// further data syncing.
type TrieSyncLeafCallback func(leaf []byte, parent common.Hash) error
// TrieSync is the main state trie synchronisation scheduler, which provides yet
// unknown trie hashes to retrieve, accepts node data associated with said hashes
// and reconstructs the trie step by step until all is done.
type TrieSync struct {
database ethdb.Database // State database for storing all the assembled node data
requests map[common.Hash]*request // Pending requests pertaining to a key hash
queue *prque.Prque // Priority queue with the pending requests
}
// NewTrieSync creates a new trie data download scheduler.
func NewTrieSync(root common.Hash, database ethdb.Database, callback TrieSyncLeafCallback) *TrieSync {
ts := &TrieSync{
database: database,
requests: make(map[common.Hash]*request),
queue: prque.New(),
}
ts.AddSubTrie(root, 0, common.Hash{}, callback)
return ts
}
// AddSubTrie registers a new trie to the sync code, rooted at the designated parent.
func (s *TrieSync) AddSubTrie(root common.Hash, depth int, parent common.Hash, callback TrieSyncLeafCallback) {
// Short circuit if the trie is empty or already known
if root == emptyRoot {
return
}
key := root.Bytes()
blob, _ := s.database.Get(key)
if local, err := decodeNode(key, blob); local != nil && err == nil {
return
}
// Assemble the new sub-trie sync request
node := node(hashNode(root.Bytes()))
req := &request{
object: &node,
hash: root,
depth: depth,
callback: callback,
}
// If this sub-trie has a designated parent, link them together
if parent != (common.Hash{}) {
ancestor := s.requests[parent]
if ancestor == nil {
panic(fmt.Sprintf("sub-trie ancestor not found: %x", parent))
}
ancestor.deps++
req.parents = append(req.parents, ancestor)
}
s.schedule(req)
}
// AddRawEntry schedules the direct retrieval of a state entry that should not be
// interpreted as a trie node, but rather accepted and stored into the database
// as is. This method's goal is to support misc state metadata retrievals (e.g.
// contract code).
func (s *TrieSync) AddRawEntry(hash common.Hash, depth int, parent common.Hash) {
// Short circuit if the entry is empty or already known
if hash == emptyState {
return
}
if blob, _ := s.database.Get(hash.Bytes()); blob != nil {
return
}
// Assemble the new sub-trie sync request
req := &request{
hash: hash,
depth: depth,
}
// If this sub-trie has a designated parent, link them together
if parent != (common.Hash{}) {
ancestor := s.requests[parent]
if ancestor == nil {
panic(fmt.Sprintf("raw-entry ancestor not found: %x", parent))
}
ancestor.deps++
req.parents = append(req.parents, ancestor)
}
s.schedule(req)
}
// Missing retrieves the known missing nodes from the trie for retrieval.
func (s *TrieSync) Missing(max int) []common.Hash {
requests := []common.Hash{}
for !s.queue.Empty() && (max == 0 || len(requests) < max) {
requests = append(requests, s.queue.PopItem().(common.Hash))
}
return requests
}
// Process injects a batch of retrieved trie nodes data.
func (s *TrieSync) Process(results []SyncResult) (int, error) {
for i, item := range results {
// If the item was not requested, bail out
request := s.requests[item.Hash]
if request == nil {
return i, ErrNotRequested
}
// If the item is a raw entry request, commit directly
if request.object == nil {
request.data = item.Data
s.commit(request, nil)
continue
}
// Decode the node data content and update the request
node, err := decodeNode(item.Hash[:], item.Data)
if err != nil {
return i, err
}
*request.object = node
request.data = item.Data
// Create and schedule a request for all the children nodes
requests, err := s.children(request)
if err != nil {
return i, err
}
if len(requests) == 0 && request.deps == 0 {
s.commit(request, nil)
continue
}
request.deps += len(requests)
for _, child := range requests {
s.schedule(child)
}
}
return 0, nil
}
// Pending returns the number of state entries currently pending for download.
func (s *TrieSync) Pending() int {
return len(s.requests)
}
// schedule inserts a new state retrieval request into the fetch queue. If there
// is already a pending request for this node, the new request will be discarded
// and only a parent reference added to the old one.
func (s *TrieSync) schedule(req *request) {
// If we're already requesting this node, add a new reference and stop
if old, ok := s.requests[req.hash]; ok {
old.parents = append(old.parents, req.parents...)
return
}
// Schedule the request for future retrieval
s.queue.Push(req.hash, float32(req.depth))
s.requests[req.hash] = req
}
// children retrieves all the missing children of a state trie entry for future
// retrieval scheduling.
func (s *TrieSync) children(req *request) ([]*request, error) {
// Gather all the children of the node, irrelevant whether known or not
type child struct {
node *node
depth int
}
children := []child{}
switch node := (*req.object).(type) {
case *shortNode:
node = node.copy() // Prevents linking all downloaded nodes together.
children = []child{{
node: &node.Val,
depth: req.depth + len(node.Key),
}}
case *fullNode:
node = node.copy()
for i := 0; i < 17; i++ {
if node.Children[i] != nil {
children = append(children, child{
node: &node.Children[i],
depth: req.depth + 1,
})
}
}
default:
panic(fmt.Sprintf("unknown node: %+v", node))
}
// Iterate over the children, and request all unknown ones
requests := make([]*request, 0, len(children))
for _, child := range children {
// Notify any external watcher of a new key/value node
if req.callback != nil {
if node, ok := (*child.node).(valueNode); ok {
if err := req.callback(node, req.hash); err != nil {
return nil, err
}
}
}
// If the child references another node, resolve or schedule
if node, ok := (*child.node).(hashNode); ok {
// Try to resolve the node from the local database
blob, _ := s.database.Get(node)
if local, err := decodeNode(node[:], blob); local != nil && err == nil {
*child.node = local
continue
}
// Locally unknown node, schedule for retrieval
requests = append(requests, &request{
object: child.node,
hash: common.BytesToHash(node),
parents: []*request{req},
depth: child.depth,
callback: req.callback,
})
}
}
return requests, nil
}
// commit finalizes a retrieval request and stores it into the database. If any
// of the referencing parent requests complete due to this commit, they are also
// committed themselves.
func (s *TrieSync) commit(req *request, batch ethdb.Batch) (err error) {
// Create a new batch if none was specified
if batch == nil {
batch = s.database.NewBatch()
defer func() {
err = batch.Write()
}()
}
// Write the node content to disk
if err := batch.Put(req.hash[:], req.data); err != nil {
return err
}
delete(s.requests, req.hash)
// Check all parents for completion
for _, parent := range req.parents {
parent.deps--
if parent.deps == 0 {
if err := s.commit(parent, batch); err != nil {
return err
}
}
}
return nil
}
