path: root/eth/sync.go

package eth

import (
    "math"
    "sync/atomic"
    "time"

    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/eth/downloader"
    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
)

// update periodically tries to synchronise with the network, both downloading
// hashes and blocks as well as retrieving cached ones.
func (pm *ProtocolManager) update() {
    forceSync := time.Tick(forceSyncCycle)
    blockProc := time.Tick(blockProcCycle)
    blockProcPend := int32(0)

    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 <-blockProc:
            // Try to pull some blocks from the downloaded
            if atomic.CompareAndSwapInt32(&blockProcPend, 0, 1) {
                go func() {
                    pm.processBlocks()
                    atomic.StoreInt32(&blockProcPend, 0)
                }()
            }

        case <-pm.quitSync:
            return
        }
    }
}

// processBlocks retrieves downloaded blocks from the download cache and tries
// to construct the local block chain with it. Note, since the block retrieval
// order matters, access to this function *must* be synchronized/serialized.
func (pm *ProtocolManager) processBlocks() error {
    pm.wg.Add(1)
    defer pm.wg.Done()

    // Short circuit if no blocks are available for insertion
    blocks := pm.downloader.TakeBlocks()
    if len(blocks) == 0 {
        return nil
    }
    glog.V(logger.Debug).Infof("Inserting chain with %d blocks (#%v - #%v)\n", len(blocks), blocks[0].RawBlock.Number(), blocks[len(blocks)-1].RawBlock.Number())

    for len(blocks) != 0 && !pm.quit {
        // Retrieve the first batch of blocks to insert
        max := int(math.Min(float64(len(blocks)), float64(blockProcAmount)))
        raw := make(types.Blocks, 0, max)
        for _, block := range blocks[:max] {
            raw = append(raw, block.RawBlock)
        }
        // Try to inset the blocks, drop the originating peer if there's an error
        index, err := pm.chainman.InsertChain(raw)
        if err != nil {
            glog.V(logger.Debug).Infoln("Downloaded block import failed:", err)
            pm.removePeer(blocks[index].OriginPeer)
            pm.downloader.Cancel()
            return err
        }
        blocks = blocks[max:]
    }
    return nil
}

// 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
    }
    // FIXME if we have the hash in our chain and the TD of the peer is
    // much higher than ours, something is wrong with us or the peer.
    // Check if the hash is on our own chain
    if pm.chainman.HasBlock(peer.recentHash) {
        glog.V(logger.Debug).Infoln("Synchronisation canceled: head already known")
        return
    }
    // Get the hashes from the peer (synchronously)
    glog.V(logger.Debug).Infof("Attempting synchronisation: %v, 0x%x", peer.id, peer.recentHash)

    err := pm.downloader.Synchronise(peer.id, peer.recentHash)
    switch err {
    case nil:
        glog.V(logger.Debug).Infof("Synchronisation completed")

    case downloader.ErrBusy:
        glog.V(logger.Debug).Infof("Synchronisation already in progress")

    case downloader.ErrTimeout, downloader.ErrBadPeer, downloader.ErrInvalidChain, downloader.ErrCrossCheckFailed:
        glog.V(logger.Debug).Infof("Removing peer %v: %v", peer.id, err)
        pm.removePeer(peer.id)

    case downloader.ErrPendingQueue:
        glog.V(logger.Debug).Infoln("Synchronisation aborted:", err)

    default:
        glog.V(logger.Warn).Infof("Synchronisation failed: %v", err)
    }
}