path: root/eth/sync.go

package eth

import (
    "math"
    "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/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
)

const (
    forceSyncCycle      = 10 * time.Second       // Time interval to force syncs, even if few peers are available
    blockProcCycle      = 500 * time.Millisecond // Time interval to check for new blocks to process
    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
    blockProcAmount     = 256
)

// 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
}

// 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)

    // 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 {
                announces[announce.hash] = announce
            }

        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, announce := range announces {
                if time.Since(announce.time) > notifyArriveTimeout {
                    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)
                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
            }
            // If any explicit fetches were replied to, import them
            if count := len(explicit); count > 0 {
                glog.V(logger.Debug).Infof("Importing %d explicitly fetched blocks", count)
                go func() {
                    for _, block := range explicit {
                        hash := block.Hash()

                        // Make sure there's still something pending to import
                        if announce := pending[hash]; announce != nil {
                            delete(pending, hash)
                            if err := pm.importBlock(announce.peer, block, 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() {
    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
    head := peer.Head()
    if pm.chainman.HasBlock(head) {
        glog.V(logger.Debug).Infoln("Synchronisation canceled: head already known")
        return
    }
    // Get the hashes from the peer (synchronously)
    glog.V(logger.Detail).Infof("Attempting synchronisation: %v, 0x%x", peer.id, head)

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

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

    case downloader.ErrTimeout, downloader.ErrBadPeer, downloader.ErrEmptyHashSet, 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)
    }
}