1 files changed, 217 insertions, 0 deletions
diff --git a/dex/sync.go b/dex/sync.go
new file mode 100644
index 000000000..e49e40087
--- /dev/null
+++ b/dex/sync.go
@@ -0,0 +1,217 @@
+// 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/rand"
+	"sync/atomic"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"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/discover"
+)
+
+const (
+	forceSyncCycle      = 10 * time.Second // Time interval to force syncs, even if few peers are available
+	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
+)
+
+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) {
+	var txs types.Transactions
+	pending, _ := pm.txpool.Pending()
+	for _, batch := range pending {
+		txs = append(txs, batch...)
+	}
+	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.
+		s.p.Log().Trace("Sending batch of transactions", "count", len(pack.txs), "bytes", 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 {
+				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
+		}
+	}
+}
+
+// syncer is responsible for periodically synchronising with the network, both
+// downloading hashes and blocks as well as handling the announcement handler.
+func (pm *ProtocolManager) syncer() {
+	// Start and ensure cleanup of sync mechanisms
+	pm.fetcher.Start()
+	defer pm.fetcher.Stop()
+	defer pm.downloader.Terminate()
+
+	// Wait for different events to fire synchronisation operations
+	forceSync := time.NewTicker(forceSyncCycle)
+	defer forceSync.Stop()
+
+	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.C:
+			// Force a sync even if not enough peers are present
+			go pm.synchronise(pm.peers.BestPeer())
+
+		case <-pm.noMorePeers:
+			return
+		}
+	}
+}
+
+// synchronise tries to sync up our local block chain with a remote peer.
+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
+	currentBlock := pm.blockchain.CurrentBlock()
+	td := pm.blockchain.GetTd(currentBlock.Hash(), currentBlock.NumberU64())
+
+	pHead, pTd := peer.Head()
+	if pTd.Cmp(td) <= 0 {
+		return
+	}
+	// Otherwise try to sync with the downloader
+	mode := downloader.FullSync
+	if atomic.LoadUint32(&pm.fastSync) == 1 {
+		// Fast sync was explicitly requested, and explicitly granted
+		mode = downloader.FastSync
+	} else if currentBlock.NumberU64() == 0 && pm.blockchain.CurrentFastBlock().NumberU64() > 0 {
+		// The database seems empty as the current block is the genesis. Yet the fast
+		// block is ahead, so fast sync was enabled for this node at a certain point.
+		// The only scenario where this can happen is if the user manually (or via a
+		// bad block) rolled back a fast sync node below the sync point. In this case
+		// however it's safe to reenable fast sync.
+		atomic.StoreUint32(&pm.fastSync, 1)
+		mode = downloader.FastSync
+	}
+
+	if mode == downloader.FastSync {
+		// Make sure the peer's total difficulty we are synchronizing is higher.
+		if pm.blockchain.GetTdByHash(pm.blockchain.CurrentFastBlock().Hash()).Cmp(pTd) >= 0 {
+			return
+		}
+	}
+
+	// Run the sync cycle, and disable fast sync if we've went past the pivot block
+	if err := pm.downloader.Synchronise(peer.id, pHead, pTd, mode); err != nil {
+		return
+	}
+	if atomic.LoadUint32(&pm.fastSync) == 1 {
+		log.Info("Fast sync complete, auto disabling")
+		atomic.StoreUint32(&pm.fastSync, 0)
+	}
+	atomic.StoreUint32(&pm.acceptTxs, 1) // Mark initial sync done
+	if head := pm.blockchain.CurrentBlock(); 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.
+		go pm.BroadcastBlock(head, false)
+	}
+}