go-ethereum/eth/downloader/syncmode.go
2025-12-19 09:36:48 +01:00

115 lines
4.3 KiB
Go

// Copyright 2025 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 (
"sync"
"github.com/ethereum/go-ethereum/core/rawdb"
"github.com/ethereum/go-ethereum/eth/ethconfig"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/log"
)
// syncModer is responsible for managing the downloader's sync mode. It takes the
// user's preference at startup and then determines the appropriate sync mode
// based on the current chain status.
type syncModer struct {
mode ethconfig.SyncMode
chain BlockChain
disk ethdb.KeyValueReader
lock sync.Mutex
}
func newSyncModer(mode ethconfig.SyncMode, chain BlockChain, disk ethdb.KeyValueReader) *syncModer {
if mode == ethconfig.FullSync {
// The database seems empty as the current block is the genesis. Yet the snap
// block is ahead, so snap sync was enabled for this node at a certain point.
// The scenarios where this can happen is
// * if the user manually (or via a bad block) rolled back a snap sync node
// below the sync point.
// * the last snap sync is not finished while user specifies a full sync this
// time. But we don't have any recent state for full sync.
// In these cases however it's safe to reenable snap sync.
fullBlock, snapBlock := chain.CurrentBlock(), chain.CurrentSnapBlock()
if fullBlock.Number.Uint64() == 0 && snapBlock.Number.Uint64() > 0 {
mode = ethconfig.SnapSync
log.Warn("Switching from full-sync to snap-sync", "reason", "snap-sync incomplete")
} else if !chain.HasState(fullBlock.Root) {
mode = ethconfig.SnapSync
log.Warn("Switching from full-sync to snap-sync", "reason", "head state missing")
} else {
// Grant the full sync mode
log.Info("Enabled full-sync", "head", fullBlock.Number, "hash", fullBlock.Hash())
}
} else {
head := chain.CurrentBlock()
if head.Number.Uint64() > 0 && chain.HasState(head.Root) {
mode = ethconfig.FullSync
log.Info("Switching from snap-sync to full-sync", "reason", "snap-sync complete")
} else {
// If snap sync was requested and our database is empty, grant it
log.Info("Enabled snap-sync", "head", head.Number, "hash", head.Hash())
}
}
return &syncModer{
mode: mode,
chain: chain,
disk: disk,
}
}
// get retrieves the current sync mode, either explicitly set, or derived
// from the chain status.
func (m *syncModer) get(report bool) ethconfig.SyncMode {
m.lock.Lock()
defer m.lock.Unlock()
// If we're in snap sync mode, return that directly
if m.mode == ethconfig.SnapSync {
return ethconfig.SnapSync
}
logger := log.Debug
if report {
logger = log.Info
}
// 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 := m.chain.CurrentBlock()
if pivot := rawdb.ReadLastPivotNumber(m.disk); pivot != nil {
if head.Number.Uint64() < *pivot {
logger("Reenabled snap-sync as chain is lagging behind the pivot", "head", head.Number, "pivot", pivot)
return ethconfig.SnapSync
}
}
// 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 !m.chain.HasState(head.Root) {
logger("Reenabled snap-sync as chain is stateless")
return ethconfig.SnapSync
}
// Nope, we're really full syncing
return ethconfig.FullSync
}
// disableSnap disables the snap sync mode, usually it's called after a successful snap sync.
func (m *syncModer) disableSnap() {
m.lock.Lock()
m.mode = ethconfig.FullSync
m.lock.Unlock()
}