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

251 lines
8.6 KiB

// 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 (
"errors"
"math/big"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/rawdb"
"github.com/ethereum/go-ethereum/eth/downloader"
"github.com/ethereum/go-ethereum/eth/protocols/eth"
"github.com/ethereum/go-ethereum/log"
)
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
)
// syncTransactions starts sending all currently pending transactions to the given peer.
func (h *handler) syncTransactions(p *eth.Peer) {
var hashes []common.Hash
for _, batch := range h.txpool.Pending(false) {
for _, tx := range batch {
hashes = append(hashes, tx.Hash)
}
}
if len(hashes) == 0 {
return
}
p.AsyncSendPooledTransactionHashes(hashes)
}
// chainSyncer coordinates blockchain sync components.
type chainSyncer struct {
handler *handler
force *time.Timer
forced bool // true when force timer fired
warned time.Time
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 *eth.Peer
td *big.Int
head common.Hash
}
// newChainSyncer creates a chainSyncer.
func newChainSyncer(handler *handler) *chainSyncer {
return &chainSyncer{
handler: handler,
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() bool {
select {
case cs.peerEventCh <- struct{}{}:
return true
case <-cs.handler.quitSync:
return false
}
}
// loop runs in its own goroutine and launches the sync when necessary.
func (cs *chainSyncer) loop() {
defer cs.handler.wg.Done()
cs.handler.blockFetcher.Start()
cs.handler.txFetcher.Start()
defer cs.handler.blockFetcher.Stop()
defer cs.handler.txFetcher.Stop()
defer cs.handler.downloader.Terminate()
// 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 err := <-cs.doneCh:
cs.doneCh = nil
cs.force.Reset(forceSyncCycle)
cs.forced = false
// If we've reached the merge transition but no beacon client is available, or
// it has not yet switched us over, keep warning the user that their infra is
// potentially flaky.
if errors.Is(err, downloader.ErrMergeTransition) && time.Since(cs.warned) > 10*time.Second {
log.Warn("Local chain is post-merge, waiting for beacon client sync switch-over...")
cs.warned = time.Now()
}
case <-cs.force.C:
cs.forced = true
case <-cs.handler.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.handler.chain.StopInsert()
cs.handler.downloader.Terminate()
if cs.doneCh != nil {
<-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
}
// If a beacon client once took over control, disable the entire legacy sync
// path from here on end. Note, there is a slight "race" between reaching TTD
// and the beacon client taking over. The downloader will enforce that nothing
// above the first TTD will be delivered to the chain for import.
//
// An alternative would be to check the local chain for exceeding the TTD and
// avoid triggering a sync in that case, but that could also miss sibling or
// other family TTD block being accepted.
if cs.handler.chain.Config().TerminalTotalDifficultyPassed || cs.handler.merger.TDDReached() {
return nil
}
// Ensure we're at minimum peer count.
minPeers := defaultMinSyncPeers
if cs.forced {
minPeers = 1
} else if minPeers > cs.handler.maxPeers {
minPeers = cs.handler.maxPeers
}
if cs.handler.peers.len() < minPeers {
return nil
}
// We have enough peers, pick the one with the highest TD, but avoid going
// over the terminal total difficulty. Above that we expect the consensus
// clients to direct the chain head to sync to.
peer := cs.handler.peers.peerWithHighestTD()
if peer == nil {
return nil
}
mode, ourTD := cs.modeAndLocalHead()
op := peerToSyncOp(mode, peer)
if op.td.Cmp(ourTD) <= 0 {
// We seem to be in sync according to the legacy rules. In the merge
// world, it can also mean we're stuck on the merge block, waiting for
// a beacon client. In the latter case, notify the user.
if ttd := cs.handler.chain.Config().TerminalTotalDifficulty; ttd != nil && ourTD.Cmp(ttd) >= 0 && time.Since(cs.warned) > 10*time.Second {
log.Warn("Local chain is post-merge, waiting for beacon client sync switch-over...")
cs.warned = time.Now()
}
return nil // We're in sync
}
return op
}
func peerToSyncOp(mode downloader.SyncMode, p *eth.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 we're in snap sync mode, return that directly
if cs.handler.snapSync.Load() {
block := cs.handler.chain.CurrentSnapBlock()
td := cs.handler.chain.GetTd(block.Hash(), block.Number.Uint64())
return downloader.SnapSync, td
}
// We are probably in full sync, but we might have rewound to before the
// snap sync pivot, check if we should re-enable snap sync.
head := cs.handler.chain.CurrentBlock()
if pivot := rawdb.ReadLastPivotNumber(cs.handler.database); pivot != nil {
if head.Number.Uint64() < *pivot {
block := cs.handler.chain.CurrentSnapBlock()
td := cs.handler.chain.GetTd(block.Hash(), block.Number.Uint64())
return downloader.SnapSync, td
}
}
// We are in a full sync, but the associated head state is missing. To complete
// the head state, forcefully rerun the snap sync. Note it doesn't mean the
// persistent state is corrupted, just mismatch with the head block.
if !cs.handler.chain.HasState(head.Root) {
block := cs.handler.chain.CurrentSnapBlock()
td := cs.handler.chain.GetTd(block.Hash(), block.Number.Uint64())
log.Info("Reenabled snap sync as chain is stateless")
return downloader.SnapSync, td
}
// Nope, we're really full syncing
td := cs.handler.chain.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.handler.doSync(op) }()
}
// doSync synchronizes the local blockchain with a remote peer.
func (h *handler) doSync(op *chainSyncOp) error {
// Run the sync cycle, and disable snap sync if we're past the pivot block
err := h.downloader.LegacySync(op.peer.ID(), op.head, op.td, h.chain.Config().TerminalTotalDifficulty, op.mode)
if err != nil {
return err
}
h.enableSyncedFeatures()
head := h.chain.CurrentBlock()
if head.Number.Uint64() > 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.
if block := h.chain.GetBlock(head.Hash(), head.Number.Uint64()); block != nil {
h.BroadcastBlock(block, false)
}
}
return nil
}