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

290 lines
8.5 KiB

package eth
import (
"math/rand"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/logger/glog"
"github.com/ethereum/go-ethereum/p2p/discover"
)
const (
forceSyncCycle = 10 * time.Second // Time interval to force syncs, even if few peers are available
notifyCheckCycle = 100 * time.Millisecond // Time interval to allow hash notifies to fulfill before hard fetching
notifyArriveTimeout = 500 * time.Millisecond // Time allowance before an announced block is explicitly requested
notifyFetchTimeout = 5 * time.Second // Maximum alloted time to return an explicitly requested block
minDesiredPeerCount = 5 // Amount of peers desired to start syncing
// This is the target size for the packs of transactions sent by txsyncLoop.
// A pack can get larger than this if a single transactions exceeds this size.
txsyncPackSize = 100 * 1024
)
// blockAnnounce is the hash notification of the availability of a new block in
// the network.
type blockAnnounce struct {
hash common.Hash
peer *peer
time time.Time
}
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) {
txs := pm.txpool.GetTransactions()
if len(txs) == 0 {
return
}
select {
case pm.txsyncCh <- &txsync{p, txs}:
case <-pm.quitSync:
}
}
// txsyncLoop 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) txsyncLoop() {
var (
pending = make(map[discover.NodeID]*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) {
// 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.
glog.V(logger.Detail).Infof("%v: sending %d transactions (%v)", s.p.Peer, len(pack.txs), size)
sending = true
go func() { done <- pack.p.sendTransactions(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 {
glog.V(logger.Debug).Infof("%v: tx send failed: %v", pack.p.Peer, err)
delete(pending, pack.p.ID())
}
// Schedule the next send.
if s := pick(); s != nil {
send(s)
}
case <-pm.quitSync:
return
}
}
}
// fetcher is responsible for collecting hash notifications, and periodically
// checking all unknown ones and individually fetching them.
func (pm *ProtocolManager) fetcher() {
announces := make(map[common.Hash][]*blockAnnounce)
request := make(map[*peer][]common.Hash)
pending := make(map[common.Hash]*blockAnnounce)
cycle := time.Tick(notifyCheckCycle)
done := make(chan common.Hash)
// Iterate the block fetching until a quit is requested
for {
select {
case notifications := <-pm.newHashCh:
// A batch of hashes the notified, schedule them for retrieval
glog.V(logger.Debug).Infof("Scheduling %d hash announcements from %s", len(notifications), notifications[0].peer.id)
for _, announce := range notifications {
// Skip if it's already pending fetch
if _, ok := pending[announce.hash]; ok {
continue
}
// Otherwise queue up the peer as a potential source
announces[announce.hash] = append(announces[announce.hash], announce)
}
case hash := <-done:
// A pending import finished, remove all traces
delete(pending, hash)
case <-cycle:
// Clean up any expired block fetches
for hash, announce := range pending {
if time.Since(announce.time) > notifyFetchTimeout {
delete(pending, hash)
}
}
// Check if any notified blocks failed to arrive
for hash, all := range announces {
if time.Since(all[0].time) > notifyArriveTimeout {
announce := all[rand.Intn(len(all))]
if !pm.chainman.HasBlock(hash) {
request[announce.peer] = append(request[announce.peer], hash)
pending[hash] = announce
}
delete(announces, hash)
}
}
if len(request) == 0 {
break
}
// Send out all block requests
for peer, hashes := range request {
glog.V(logger.Debug).Infof("Explicitly fetching %d blocks from %s", len(hashes), peer.id)
go peer.requestBlocks(hashes)
}
request = make(map[*peer][]common.Hash)
case filter := <-pm.newBlockCh:
// Blocks arrived, extract any explicit fetches, return all else
var blocks types.Blocks
select {
case blocks = <-filter:
case <-pm.quitSync:
return
}
explicit, download := []*types.Block{}, []*types.Block{}
for _, block := range blocks {
hash := block.Hash()
// Filter explicitly requested blocks from hash announcements
if _, ok := pending[hash]; ok {
// Discard if already imported by other means
if !pm.chainman.HasBlock(hash) {
explicit = append(explicit, block)
} else {
delete(pending, hash)
}
} else {
download = append(download, block)
}
}
select {
case filter <- download:
case <-pm.quitSync:
return
}
// Create a closure with the retrieved blocks and origin peers
peers := make([]*peer, 0, len(explicit))
blocks = make([]*types.Block, 0, len(explicit))
for _, block := range explicit {
hash := block.Hash()
if announce := pending[hash]; announce != nil {
// Drop the block if it surely cannot fit
if pm.chainman.HasBlock(hash) || !pm.chainman.HasBlock(block.ParentHash()) {
// delete(pending, hash) // if we drop, it will re-fetch it, wait for timeout?
continue
}
// Otherwise accumulate for import
peers = append(peers, announce.peer)
blocks = append(blocks, block)
}
}
// If any explicit fetches were replied to, import them
if count := len(blocks); count > 0 {
glog.V(logger.Debug).Infof("Importing %d explicitly fetched blocks", len(blocks))
go func() {
// Make sure all hashes are cleaned up
for _, block := range blocks {
hash := block.Hash()
defer func() { done <- hash }()
}
// Try and actually import the blocks
for i := 0; i < len(blocks); i++ {
if err := pm.importBlock(peers[i], blocks[i], nil); err != nil {
glog.V(logger.Detail).Infof("Failed to import explicitly fetched block: %v", err)
return
}
}
}()
}
case <-pm.quitSync:
return
}
}
}
// syncer is responsible for periodically synchronising with the network, both
// downloading hashes and blocks as well as retrieving cached ones.
func (pm *ProtocolManager) syncer() {
// Abort any pending syncs if we terminate
defer pm.downloader.Cancel()
forceSync := time.Tick(forceSyncCycle)
for {
select {
case <-pm.newPeerCh:
// Make sure we have peers to select from, then sync
if pm.peers.Len() < minDesiredPeerCount {
break
}
go pm.synchronise(pm.peers.BestPeer())
case <-forceSync:
// Force a sync even if not enough peers are present
go pm.synchronise(pm.peers.BestPeer())
case <-pm.quitSync:
return
}
}
}
// synchronise tries to sync up our local block chain with a remote peer, both
// adding various sanity checks as well as wrapping it with various log entries.
func (pm *ProtocolManager) synchronise(peer *peer) {
// Short circuit if no peers are available
if peer == nil {
return
}
// Make sure the peer's TD is higher than our own. If not drop.
if peer.Td().Cmp(pm.chainman.Td()) <= 0 {
return
}
// Otherwise try to sync with the downloader
pm.downloader.Synchronise(peer.id, peer.Head())
}