// 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/dexon-foundation/dexon/common"
"github.com/dexon-foundation/dexon/common/prque"
"github.com/dexon-foundation/dexon/ethdb"
)
// 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")
// ErrAlreadyProcessed is returned by the trie sync when it's requested to process a
// node it already processed previously.
var ErrAlreadyProcessed = errors.New("already processed")
// 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
raw bool // Whether this is a raw entry (code) or a trie node
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 LeafCallback // 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
}
// syncMemBatch is an in-memory buffer of successfully downloaded but not yet
// persisted data items.
type syncMemBatch struct {
batch map[common.Hash][]byte // In-memory membatch of recently completed items
order []common.Hash // Order of completion to prevent out-of-order data loss
}
// newSyncMemBatch allocates a new memory-buffer for not-yet persisted trie nodes.
func newSyncMemBatch() *syncMemBatch {
return &syncMemBatch{
batch: make(map[common.Hash][]byte),
order: make([]common.Hash, 0, 256),
}
}
// Sync 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 Sync struct {
database DatabaseReader // Persistent database to check for existing entries
membatch *syncMemBatch // Memory buffer to avoid frequent database writes
requests map[common.Hash]*request // Pending requests pertaining to a key hash
queue *prque.Prque // Priority queue with the pending requests
}
// NewSync creates a new trie data download scheduler.
func NewSync(root common.Hash, database DatabaseReader, callback LeafCallback) *Sync {
ts := &Sync{
database: database,
membatch: newSyncMemBatch(),
requests: make(map[common.Hash]*request),
queue: prque.New(nil),
}
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 *Sync) AddSubTrie(root common.Hash, depth int, parent common.Hash, callback LeafCallback) {
// Short circuit if the trie is empty or already known
if root == emptyRoot {
return
}
if _, ok := s.membatch.batch[root]; ok {
return
}
key := root.Bytes()
blob, _ := s.database.Get(key)
if local, err := decodeNode(key, blob, 0); local != nil && err == nil {
return
}
// Assemble the new sub-trie sync request
req := &request{
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 *Sync) AddRawEntry(hash common.Hash, depth int, parent common.Hash) {
// Short circuit if the entry is empty or already known
if hash == emptyState {
return
}
if _, ok := s.membatch.batch[hash]; ok {
return
}
if ok, _ := s.database.Has(hash.Bytes()); ok {
return
}
// Assemble the new sub-trie sync request
req := &request{
hash: hash,
raw: true,
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 *Sync) 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, returning if something
// was committed to the database and also the index of an entry if processing of
// it failed.
func (s *Sync) Process(results []SyncResult) (bool, int, error) {
committed := false
for i, item := range results {
// If the item was not requested, bail out
request := s.requests[item.Hash]
if request == nil {
return committed, i, ErrNotRequested
}
if request.data != nil {
return committed, i, ErrAlreadyProcessed
}
// If the item is a raw entry request, commit directly
if request.raw {
request.data = item.Data
s.commit(request)
committed = true
continue
}
// Decode the node data content and update the request
node, err := decodeNode(item.Hash[:], item.Data, 0)
if err != nil {
return committed, i, err
}
request.data = item.Data
// Create and schedule a request for all the children nodes
requests, err := s.children(request, node)
if err != nil {
return committed, i, err
}
if len(requests) == 0 && request.deps == 0 {
s.commit(request)
committed = true
continue
}
request.deps += len(requests)
for _, child := range requests {
s.schedule(child)
}
}
return committed, 0, nil
}
// Commit flushes the data stored in the internal membatch out to persistent
// storage, returning the number of items written and any occurred error.
func (s *Sync) Commit(dbw ethdb.Putter) (int, error) {
// Dump the membatch into a database dbw
for i, key := range s.membatch.order {
if err := dbw.Put(key[:], s.membatch.batch[key]); err != nil {
return i, err
}
}
written := len(s.membatch.order)
// Drop the membatch data and return
s.membatch = newSyncMemBatch()
return written, nil
}
// Pending returns the number of state entries currently pending for download.
func (s *Sync) 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 *Sync) 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, int64(req.depth))
s.requests[req.hash] = req
}
// children retrieves all the missing children of a state trie entry for future
// retrieval scheduling.
func (s *Sync) children(req *request, object node) ([]*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 := (object).(type) {
case *shortNode:
children = []child{{
node: node.Val,
depth: req.depth + len(node.Key),
}}
case *fullNode:
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
hash := common.BytesToHash(node)
if _, ok := s.membatch.batch[hash]; ok {
continue
}
if ok, _ := s.database.Has(node); ok {
continue
}
// Locally unknown node, schedule for retrieval
requests = append(requests, &request{
hash: hash,
parents: []*request{req},
depth: child.depth,
callback: req.callback,
})
}
}
return requests, nil
}
// commit finalizes a retrieval request and stores it into the membatch. If any
// of the referencing parent requests complete due to this commit, they are also
// committed themselves.
func (s *Sync) commit(req *request) (err error) {
// Write the node content to the membatch
s.membatch.batch[req.hash] = req.data
s.membatch.order = append(s.membatch.order, req.hash)
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); err != nil {
return err
}
}
}
return nil
}
