// Copyright 2017 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 downloader
import (
"fmt"
"hash"
"sync"
"time"
"github.com/dexon-foundation/dexon/common"
"github.com/dexon-foundation/dexon/core/rawdb"
"github.com/dexon-foundation/dexon/core/state"
"github.com/dexon-foundation/dexon/ethdb"
"github.com/dexon-foundation/dexon/log"
"github.com/dexon-foundation/dexon/trie"
"golang.org/x/crypto/sha3"
)
// stateReq represents a batch of state fetch requests grouped together into
// a single data retrieval network packet.
type stateReq struct {
items []common.Hash // Hashes of the state items to download
tasks map[common.Hash]*stateTask // Download tasks to track previous attempts
timeout time.Duration // Maximum round trip time for this to complete
timer *time.Timer // Timer to fire when the RTT timeout expires
peer *peerConnection // Peer that we're requesting from
response [][]byte // Response data of the peer (nil for timeouts)
dropped bool // Flag whether the peer dropped off early
}
// timedOut returns if this request timed out.
func (req *stateReq) timedOut() bool {
return req.response == nil
}
// stateSyncStats is a collection of progress stats to report during a state trie
// sync to RPC requests as well as to display in user logs.
type stateSyncStats struct {
processed uint64 // Number of state entries processed
duplicate uint64 // Number of state entries downloaded twice
unexpected uint64 // Number of non-requested state entries received
pending uint64 // Number of still pending state entries
}
// syncState starts downloading state with the given root hash.
func (d *Downloader) syncState(root common.Hash) *stateSync {
s := newStateSync(d, root)
select {
case d.stateSyncStart <- s:
case <-d.quitCh:
s.err = errCancelStateFetch
close(s.done)
}
return s
}
// stateFetcher manages the active state sync and accepts requests
// on its behalf.
func (d *Downloader) stateFetcher() {
for {
select {
case s := <-d.stateSyncStart:
for next := s; next != nil; {
next = d.runStateSync(next)
}
case <-d.stateCh:
// Ignore state responses while no sync is running.
case <-d.quitCh:
return
}
}
}
// runStateSync runs a state synchronisation until it completes or another root
// hash is requested to be switched over to.
func (d *Downloader) runStateSync(s *stateSync) *stateSync {
var (
active = make(map[string]*stateReq) // Currently in-flight requests
finished []*stateReq // Completed or failed requests
timeout = make(chan *stateReq) // Timed out active requests
)
defer func() {
// Cancel active request timers on exit. Also set peers to idle so they're
// available for the next sync.
for _, req := range active {
req.timer.Stop()
req.peer.SetNodeDataIdle(len(req.items))
}
}()
// Run the state sync.
go s.run()
defer s.Cancel()
// Listen for peer departure events to cancel assigned tasks
peerDrop := make(chan *peerConnection, 1024)
peerSub := s.d.peers.SubscribePeerDrops(peerDrop)
defer peerSub.Unsubscribe()
for {
// Enable sending of the first buffered element if there is one.
var (
deliverReq *stateReq
deliverReqCh chan *stateReq
)
if len(finished) > 0 {
deliverReq = finished[0]
deliverReqCh = s.deliver
}
select {
// The stateSync lifecycle:
case next := <-d.stateSyncStart:
return next
case <-s.done:
return nil
// Send the next finished request to the current sync:
case deliverReqCh <- deliverReq:
// Shift out the first request, but also set the emptied slot to nil for GC
copy(finished, finished[1:])
finished[len(finished)-1] = nil
finished = finished[:len(finished)-1]
// Handle incoming state packs:
case pack := <-d.stateCh:
// Discard any data not requested (or previously timed out)
req := active[pack.PeerId()]
if req == nil {
log.Debug("Unrequested node data", "peer", pack.PeerId(), "len", pack.Items())
continue
}
// Finalize the request and queue up for processing
req.timer.Stop()
req.response = pack.(*statePack).states
finished = append(finished, req)
delete(active, pack.PeerId())
// Handle dropped peer connections:
case p := <-peerDrop:
// Skip if no request is currently pending
req := active[p.id]
if req == nil {
continue
}
// Finalize the request and queue up for processing
req.timer.Stop()
req.dropped = true
finished = append(finished, req)
delete(active, p.id)
// Handle timed-out requests:
case req := <-timeout:
// If the peer is already requesting something else, ignore the stale timeout.
// This can happen when the timeout and the delivery happens simultaneously,
// causing both pathways to trigger.
if active[req.peer.id] != req {
continue
}
// Move the timed out data back into the download queue
finished = append(finished, req)
delete(active, req.peer.id)
// Track outgoing state requests:
case req := <-d.trackStateReq:
// If an active request already exists for this peer, we have a problem. In
// theory the trie node schedule must never assign two requests to the same
// peer. In practice however, a peer might receive a request, disconnect and
// immediately reconnect before the previous times out. In this case the first
// request is never honored, alas we must not silently overwrite it, as that
// causes valid requests to go missing and sync to get stuck.
if old := active[req.peer.id]; old != nil {
log.Warn("Busy peer assigned new state fetch", "peer", old.peer.id)
// Make sure the previous one doesn't get siletly lost
old.timer.Stop()
old.dropped = true
finished = append(finished, old)
}
// Start a timer to notify the sync loop if the peer stalled.
req.timer = time.AfterFunc(req.timeout, func() {
select {
case timeout <- req:
case <-s.done:
// Prevent leaking of timer goroutines in the unlikely case where a
// timer is fired just before exiting runStateSync.
}
})
active[req.peer.id] = req
}
}
}
// stateSync schedules requests for downloading a particular state trie defined
// by a given state root.
type stateSync struct {
d *Downloader // Downloader instance to access and manage current peerset
sched *trie.Sync // State trie sync scheduler defining the tasks
keccak hash.Hash // Keccak256 hasher to verify deliveries with
tasks map[common.Hash]*stateTask // Set of tasks currently queued for retrieval
numUncommitted int
bytesUncommitted int
deliver chan *stateReq // Delivery channel multiplexing peer responses
cancel chan struct{} // Channel to signal a termination request
cancelOnce sync.Once // Ensures cancel only ever gets called once
done chan struct{} // Channel to signal termination completion
err error // Any error hit during sync (set before completion)
}
// stateTask represents a single trie node download task, containing a set of
// peers already attempted retrieval from to detect stalled syncs and abort.
type stateTask struct {
attempts map[string]struct{}
}
// newStateSync creates a new state trie download scheduler. This method does not
// yet start the sync. The user needs to call run to initiate.
func newStateSync(d *Downloader, root common.Hash) *stateSync {
return &stateSync{
d: d,
sched: state.NewStateSync(root, d.stateDB),
keccak: sha3.NewLegacyKeccak256(),
tasks: make(map[common.Hash]*stateTask),
deliver: make(chan *stateReq),
cancel: make(chan struct{}),
done: make(chan struct{}),
}
}
// run starts the task assignment and response processing loop, blocking until
// it finishes, and finally notifying any goroutines waiting for the loop to
// finish.
func (s *stateSync) run() {
s.err = s.loop()
close(s.done)
}
// Wait blocks until the sync is done or canceled.
func (s *stateSync) Wait() error {
<-s.done
return s.err
}
// Cancel cancels the sync and waits until it has shut down.
func (s *stateSync) Cancel() error {
s.cancelOnce.Do(func() { close(s.cancel) })
return s.Wait()
}
// loop is the main event loop of a state trie sync. It it responsible for the
// assignment of new tasks to peers (including sending it to them) as well as
// for the processing of inbound data. Note, that the loop does not directly
// receive data from peers, rather those are buffered up in the downloader and
// pushed here async. The reason is to decouple processing from data receipt
// and timeouts.
func (s *stateSync) loop() (err error) {
// Listen for new peer events to assign tasks to them
newPeer := make(chan *peerConnection, 1024)
peerSub := s.d.peers.SubscribeNewPeers(newPeer)
defer peerSub.Unsubscribe()
defer func() {
cerr := s.commit(true)
if err == nil {
err = cerr
}
}()
// Keep assigning new tasks until the sync completes or aborts
for s.sched.Pending() > 0 {
if err = s.commit(false); err != nil {
return err
}
s.assignTasks()
// Tasks assigned, wait for something to happen
select {
case <-newPeer:
// New peer arrived, try to assign it download tasks
case <-s.cancel:
return errCancelStateFetch
case <-s.d.cancelCh:
return errCancelStateFetch
case req := <-s.deliver:
// Response, disconnect or timeout triggered, drop the peer if stalling
log.Trace("Received node data response", "peer", req.peer.id, "count", len(req.response), "dropped", req.dropped, "timeout", !req.dropped && req.timedOut())
if len(req.items) <= 2 && !req.dropped && req.timedOut() {
// 2 items are the minimum requested, if even that times out, we've no use of
// this peer at the moment.
log.Warn("Stalling state sync, dropping peer", "peer", req.peer.id)
s.d.dropPeer(req.peer.id)
}
// Process all the received blobs and check for stale delivery
delivered, err := s.process(req)
if err != nil {
log.Warn("Node data write error", "err", err)
return err
}
req.peer.SetNodeDataIdle(delivered)
}
}
return nil
}
func (s *stateSync) commit(force bool) error {
if !force && s.bytesUncommitted < ethdb.IdealBatchSize {
return nil
}
start := time.Now()
b := s.d.stateDB.NewBatch()
if written, err := s.sched.Commit(b); written == 0 || err != nil {
return err
}
if err := b.Write(); err != nil {
return fmt.Errorf("DB write error: %v", err)
}
s.updateStats(s.numUncommitted, 0, 0, time.Since(start))
s.numUncommitted = 0
s.bytesUncommitted = 0
return nil
}
// assignTasks attempts to assign new tasks to all idle peers, either from the
// batch currently being retried, or fetching new data from the trie sync itself.
func (s *stateSync) assignTasks() {
// Iterate over all idle peers and try to assign them state fetches
peers, _ := s.d.peers.NodeDataIdlePeers()
for _, p := range peers {
// Assign a batch of fetches proportional to the estimated latency/bandwidth
cap := p.NodeDataCapacity(s.d.requestRTT())
req := &stateReq{peer: p, timeout: s.d.requestTTL()}
s.fillTasks(cap, req)
// If the peer was assigned tasks to fetch, send the network request
if len(req.items) > 0 {
req.peer.log.Trace("Requesting new batch of data", "type", "state", "count", len(req.items))
select {
case s.d.trackStateReq <- req:
req.peer.FetchNodeData(req.items)
case <-s.cancel:
case <-s.d.cancelCh:
}
}
}
}
// fillTasks fills the given request object with a maximum of n state download
// tasks to send to the remote peer.
func (s *stateSync) fillTasks(n int, req *stateReq) {
// Refill available tasks from the scheduler.
if len(s.tasks) < n {
new := s.sched.Missing(n - len(s.tasks))
for _, hash := range new {
s.tasks[hash] = &stateTask{make(map[string]struct{})}
}
}
// Find tasks that haven't been tried with the request's peer.
req.items = make([]common.Hash, 0, n)
req.tasks = make(map[common.Hash]*stateTask, n)
for hash, t := range s.tasks {
// Stop when we've gathered enough requests
if len(req.items) == n {
break
}
// Skip any requests we've already tried from this peer
if _, ok := t.attempts[req.peer.id]; ok {
continue
}
// Assign the request to this peer
t.attempts[req.peer.id] = struct{}{}
req.items = append(req.items, hash)
req.tasks[hash] = t
delete(s.tasks, hash)
}
}
// process iterates over a batch of delivered state data, injecting each item
// into a running state sync, re-queuing any items that were requested but not
// delivered.
// Returns whether the peer actually managed to deliver anything of value,
// and any error that occurred
func (s *stateSync) process(req *stateReq) (int, error) {
// Collect processing stats and update progress if valid data was received
duplicate, unexpected, successful := 0, 0, 0
defer func(start time.Time) {
if duplicate > 0 || unexpected > 0 {
s.updateStats(0, duplicate, unexpected, time.Since(start))
}
}(time.Now())
// Iterate over all the delivered data and inject one-by-one into the trie
progress := false
for _, blob := range req.response {
prog, hash, err := s.processNodeData(blob)
switch err {
case nil:
s.numUncommitted++
s.bytesUncommitted += len(blob)
progress = progress || prog
successful++
case trie.ErrNotRequested:
unexpected++
case trie.ErrAlreadyProcessed:
duplicate++
default:
return successful, fmt.Errorf("invalid state node %s: %v", hash.TerminalString(), err)
}
if _, ok := req.tasks[hash]; ok {
delete(req.tasks, hash)
}
}
// Put unfulfilled tasks back into the retry queue
npeers := s.d.peers.Len()
for hash, task := range req.tasks {
// If the node did deliver something, missing items may be due to a protocol
// limit or a previous timeout + delayed delivery. Both cases should permit
// the node to retry the missing items (to avoid single-peer stalls).
if len(req.response) > 0 || req.timedOut() {
delete(task.attempts, req.peer.id)
}
// If we've requested the node too many times already, it may be a malicious
// sync where nobody has the right data. Abort.
if len(task.attempts) >= npeers {
return successful, fmt.Errorf("state node %s failed with all peers (%d tries, %d peers)", hash.TerminalString(), len(task.attempts), npeers)
}
// Missing item, place into the retry queue.
s.tasks[hash] = task
}
return successful, nil
}
// processNodeData tries to inject a trie node data blob delivered from a remote
// peer into the state trie, returning whether anything useful was written or any
// error occurred.
func (s *stateSync) processNodeData(blob []byte) (bool, common.Hash, error) {
res := trie.SyncResult{Data: blob}
s.keccak.Reset()
s.keccak.Write(blob)
s.keccak.Sum(res.Hash[:0])
committed, _, err := s.sched.Process([]trie.SyncResult{res})
return committed, res.Hash, err
}
// updateStats bumps the various state sync progress counters and displays a log
// message for the user to see.
func (s *stateSync) updateStats(written, duplicate, unexpected int, duration time.Duration) {
s.d.syncStatsLock.Lock()
defer s.d.syncStatsLock.Unlock()
s.d.syncStatsState.pending = uint64(s.sched.Pending())
s.d.syncStatsState.processed += uint64(written)
s.d.syncStatsState.duplicate += uint64(duplicate)
s.d.syncStatsState.unexpected += uint64(unexpected)
if written > 0 || duplicate > 0 || unexpected > 0 {
log.Info("Imported new state entries", "count", written, "elapsed", common.PrettyDuration(duration), "processed", s.d.syncStatsState.processed, "pending", s.d.syncStatsState.pending, "retry", len(s.tasks), "duplicate", s.d.syncStatsState.duplicate, "unexpected", s.d.syncStatsState.unexpected)
}
if written > 0 {
rawdb.WriteFastTrieProgress(s.d.stateDB, s.d.syncStatsState.processed)
}
}
