Official Go implementation of the Ethereum protocol
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go-ethereum/eth/sync.go

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// 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 eth
import (
"math/big"
"math/rand"
"sync/atomic"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/rawdb"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/eth/downloader"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/p2p/enode"
)
const (
forceSyncCycle = 10 * time.Second // Time interval to force syncs, even if few peers are available
defaultMinSyncPeers = 5 // Amount of peers desired to start syncing
// This is the target size for the packs of transactions sent by txsyncLoop64.
// A pack can get larger than this if a single transactions exceeds this size.
txsyncPackSize = 100 * 1024
)
type txsync struct {
p *peer
txs []*types.Transaction
}
// syncTransactions starts sending all currently pending transactions to the given peer.
func (pm *ProtocolManager) syncTransactions(p *peer) {
// Assemble the set of transaction to broadcast or announce to the remote
// peer. Fun fact, this is quite an expensive operation as it needs to sort
// the transactions if the sorting is not cached yet. However, with a random
// order, insertions could overflow the non-executable queues and get dropped.
//
// TODO(karalabe): Figure out if we could get away with random order somehow
var txs types.Transactions
pending, _ := pm.txpool.Pending()
for _, batch := range pending {
txs = append(txs, batch...)
}
if len(txs) == 0 {
return
}
// The eth/65 protocol introduces proper transaction announcements, so instead
// of dripping transactions across multiple peers, just send the entire list as
// an announcement and let the remote side decide what they need (likely nothing).
if p.version >= eth65 {
hashes := make([]common.Hash, len(txs))
for i, tx := range txs {
hashes[i] = tx.Hash()
}
p.AsyncSendPooledTransactionHashes(hashes)
return
}
// Out of luck, peer is running legacy protocols, drop the txs over
select {
case pm.txsyncCh <- &txsync{p: p, txs: txs}:
case <-pm.quitSync:
}
}
// txsyncLoop64 takes care of the initial transaction sync for each new
// connection. When a new peer appears, we relay all currently pending
// transactions. In order to minimise egress bandwidth usage, we send
// the transactions in small packs to one peer at a time.
func (pm *ProtocolManager) txsyncLoop64() {
defer pm.wg.Done()
var (
pending = make(map[enode.ID]*txsync)
sending = false // whether a send is active
pack = new(txsync) // the pack that is being sent
done = make(chan error, 1) // result of the send
)
// send starts a sending a pack of transactions from the sync.
send := func(s *txsync) {
if s.p.version >= eth65 {
panic("initial transaction syncer running on eth/65+")
}
// Fill pack with transactions up to the target size.
size := common.StorageSize(0)
pack.p = s.p
pack.txs = pack.txs[:0]
for i := 0; i < len(s.txs) && size < txsyncPackSize; i++ {
pack.txs = append(pack.txs, s.txs[i])
size += s.txs[i].Size()
}
// Remove the transactions that will be sent.
s.txs = s.txs[:copy(s.txs, s.txs[len(pack.txs):])]
if len(s.txs) == 0 {
delete(pending, s.p.ID())
}
// Send the pack in the background.
s.p.Log().Trace("Sending batch of transactions", "count", len(pack.txs), "bytes", size)
sending = true
go func() { done <- pack.p.SendTransactions64(pack.txs) }()
}
// pick chooses the next pending sync.
pick := func() *txsync {
if len(pending) == 0 {
return nil
}
n := rand.Intn(len(pending)) + 1
for _, s := range pending {
if n--; n == 0 {
return s
}
}
return nil
}
for {
select {
case s := <-pm.txsyncCh:
pending[s.p.ID()] = s
if !sending {
send(s)
}
case err := <-done:
sending = false
// Stop tracking peers that cause send failures.
if err != nil {
pack.p.Log().Debug("Transaction send failed", "err", err)
delete(pending, pack.p.ID())
}
// Schedule the next send.
if s := pick(); s != nil {
send(s)
}
case <-pm.quitSync:
return
}
}
}
// chainSyncer coordinates blockchain sync components.
type chainSyncer struct {
pm *ProtocolManager
force *time.Timer
forced bool // true when force timer fired
peerEventCh chan struct{}
doneCh chan error // non-nil when sync is running
}
// chainSyncOp is a scheduled sync operation.
type chainSyncOp struct {
mode downloader.SyncMode
peer *peer
td *big.Int
head common.Hash
}
// newChainSyncer creates a chainSyncer.
func newChainSyncer(pm *ProtocolManager) *chainSyncer {
return &chainSyncer{
pm: pm,
peerEventCh: make(chan struct{}),
}
}
// handlePeerEvent notifies the syncer about a change in the peer set.
// This is called for new peers and every time a peer announces a new
// chain head.
func (cs *chainSyncer) handlePeerEvent(p *peer) bool {
select {
case cs.peerEventCh <- struct{}{}:
return true
case <-cs.pm.quitSync:
return false
}
}
// loop runs in its own goroutine and launches the sync when necessary.
func (cs *chainSyncer) loop() {
defer cs.pm.wg.Done()
cs.pm.blockFetcher.Start()
cs.pm.txFetcher.Start()
defer cs.pm.blockFetcher.Stop()
defer cs.pm.txFetcher.Stop()
// The force timer lowers the peer count threshold down to one when it fires.
// This ensures we'll always start sync even if there aren't enough peers.
cs.force = time.NewTimer(forceSyncCycle)
defer cs.force.Stop()
for {
if op := cs.nextSyncOp(); op != nil {
cs.startSync(op)
}
select {
case <-cs.peerEventCh:
// Peer information changed, recheck.
case <-cs.doneCh:
cs.doneCh = nil
cs.force.Reset(forceSyncCycle)
cs.forced = false
case <-cs.force.C:
cs.forced = true
case <-cs.pm.quitSync:
// Disable all insertion on the blockchain. This needs to happen before
// terminating the downloader because the downloader waits for blockchain
// inserts, and these can take a long time to finish.
cs.pm.blockchain.StopInsert()
cs.pm.downloader.Terminate()
if cs.doneCh != nil {
// Wait for the current sync to end.
<-cs.doneCh
}
return
}
}
}
// nextSyncOp determines whether sync is required at this time.
func (cs *chainSyncer) nextSyncOp() *chainSyncOp {
if cs.doneCh != nil {
return nil // Sync already running.
}
// Ensure we're at minimum peer count.
minPeers := defaultMinSyncPeers
if cs.forced {
minPeers = 1
} else if minPeers > cs.pm.maxPeers {
minPeers = cs.pm.maxPeers
}
if cs.pm.peers.Len() < minPeers {
return nil
}
// We have enough peers, check TD.
peer := cs.pm.peers.BestPeer()
if peer == nil {
return nil
}
mode, ourTD := cs.modeAndLocalHead()
op := peerToSyncOp(mode, peer)
if op.td.Cmp(ourTD) <= 0 {
return nil // We're in sync.
}
return op
}
func peerToSyncOp(mode downloader.SyncMode, p *peer) *chainSyncOp {
peerHead, peerTD := p.Head()
return &chainSyncOp{mode: mode, peer: p, td: peerTD, head: peerHead}
}
func (cs *chainSyncer) modeAndLocalHead() (downloader.SyncMode, *big.Int) {
if atomic.LoadUint32(&cs.pm.fastSync) == 1 {
block := cs.pm.blockchain.CurrentFastBlock()
td := cs.pm.blockchain.GetTdByHash(block.Hash())
return downloader.FastSync, td
} else {
head := cs.pm.blockchain.CurrentHeader()
td := cs.pm.blockchain.GetTd(head.Hash(), head.Number.Uint64())
return downloader.FullSync, td
}
}
// startSync launches doSync in a new goroutine.
func (cs *chainSyncer) startSync(op *chainSyncOp) {
cs.doneCh = make(chan error, 1)
go func() { cs.doneCh <- cs.pm.doSync(op) }()
}
// doSync synchronizes the local blockchain with a remote peer.
func (pm *ProtocolManager) doSync(op *chainSyncOp) error {
if op.mode == downloader.FastSync {
// Before launch the fast sync, we have to ensure user uses the same
// txlookup limit.
// The main concern here is: during the fast sync Geth won't index the
// block(generate tx indices) before the HEAD-limit. But if user changes
// the limit in the next fast sync(e.g. user kill Geth manually and
// restart) then it will be hard for Geth to figure out the oldest block
// has been indexed. So here for the user-experience wise, it's non-optimal
// that user can't change limit during the fast sync. If changed, Geth
// will just blindly use the original one.
limit := pm.blockchain.TxLookupLimit()
if stored := rawdb.ReadFastTxLookupLimit(pm.chaindb); stored == nil {
rawdb.WriteFastTxLookupLimit(pm.chaindb, limit)
} else if *stored != limit {
pm.blockchain.SetTxLookupLimit(*stored)
log.Warn("Update txLookup limit", "provided", limit, "updated", *stored)
}
}
// Run the sync cycle, and disable fast sync if we're past the pivot block
err := pm.downloader.Synchronise(op.peer.id, op.head, op.td, op.mode)
if err != nil {
return err
}
if atomic.LoadUint32(&pm.fastSync) == 1 {
log.Info("Fast sync complete, auto disabling")
atomic.StoreUint32(&pm.fastSync, 0)
}
// If we've successfully finished a sync cycle and passed any required checkpoint,
// enable accepting transactions from the network.
head := pm.blockchain.CurrentBlock()
if head.NumberU64() >= pm.checkpointNumber {
// Checkpoint passed, sanity check the timestamp to have a fallback mechanism
// for non-checkpointed (number = 0) private networks.
if head.Time() >= uint64(time.Now().AddDate(0, -1, 0).Unix()) {
atomic.StoreUint32(&pm.acceptTxs, 1)
}
}
if head.NumberU64() > 0 {
// We've completed a sync cycle, notify all peers of new state. This path is
// essential in star-topology networks where a gateway node needs to notify
// all its out-of-date peers of the availability of a new block. This failure
// scenario will most often crop up in private and hackathon networks with
// degenerate connectivity, but it should be healthy for the mainnet too to
// more reliably update peers or the local TD state.
pm.BroadcastBlock(head, false)
}
return nil
}