github.com/xfond/eth-implementation@v1.8.9-0.20180514135602-f6bc65fc6811/les/sync.go (about)

     1  // Copyright 2016 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package les
    18  
    19  import (
    20  	"context"
    21  	"time"
    22  
    23  	"github.com/ethereum/go-ethereum/core/rawdb"
    24  	"github.com/ethereum/go-ethereum/eth/downloader"
    25  	"github.com/ethereum/go-ethereum/light"
    26  )
    27  
    28  // syncer is responsible for periodically synchronising with the network, both
    29  // downloading hashes and blocks as well as handling the announcement handler.
    30  func (pm *ProtocolManager) syncer() {
    31  	// Start and ensure cleanup of sync mechanisms
    32  	//pm.fetcher.Start()
    33  	//defer pm.fetcher.Stop()
    34  	defer pm.downloader.Terminate()
    35  
    36  	// Wait for different events to fire synchronisation operations
    37  	//forceSync := time.Tick(forceSyncCycle)
    38  	for {
    39  		select {
    40  		case <-pm.newPeerCh:
    41  			/*			// Make sure we have peers to select from, then sync
    42  						if pm.peers.Len() < minDesiredPeerCount {
    43  							break
    44  						}
    45  						go pm.synchronise(pm.peers.BestPeer())
    46  			*/
    47  		/*case <-forceSync:
    48  		// Force a sync even if not enough peers are present
    49  		go pm.synchronise(pm.peers.BestPeer())
    50  		*/
    51  		case <-pm.noMorePeers:
    52  			return
    53  		}
    54  	}
    55  }
    56  
    57  func (pm *ProtocolManager) needToSync(peerHead blockInfo) bool {
    58  	head := pm.blockchain.CurrentHeader()
    59  	currentTd := rawdb.ReadTd(pm.chainDb, head.Hash(), head.Number.Uint64())
    60  	return currentTd != nil && peerHead.Td.Cmp(currentTd) > 0
    61  }
    62  
    63  // synchronise tries to sync up our local block chain with a remote peer.
    64  func (pm *ProtocolManager) synchronise(peer *peer) {
    65  	// Short circuit if no peers are available
    66  	if peer == nil {
    67  		return
    68  	}
    69  
    70  	// Make sure the peer's TD is higher than our own.
    71  	if !pm.needToSync(peer.headBlockInfo()) {
    72  		return
    73  	}
    74  
    75  	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
    76  	defer cancel()
    77  	pm.blockchain.(*light.LightChain).SyncCht(ctx)
    78  	pm.downloader.Synchronise(peer.id, peer.Head(), peer.Td(), downloader.LightSync)
    79  }