package downloader
import (
"errors"
"fmt"
"sync"
"sync/atomic"
"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"
"gopkg.in/fatih/set.v0"
)
const (
maxBlockFetch = 256 // Amount of max blocks to be fetched per chunk
peerCountTimeout = 12 * time.Second // Amount of time it takes for the peer handler to ignore minDesiredPeerCount
hashTtl = 20 * time.Second // The amount of time it takes for a hash request to time out
)
var (
minDesiredPeerCount = 5 // Amount of peers desired to start syncing
blockTtl = 20 * time.Second // The amount of time it takes for a block request to time out
errLowTd = errors.New("peer's TD is too low")
errBusy = errors.New("busy")
errUnknownPeer = errors.New("peer's unknown or unhealthy")
ErrBadPeer = errors.New("action from bad peer ignored")
errNoPeers = errors.New("no peers to keep download active")
errPendingQueue = errors.New("pending items in queue")
errTimeout = errors.New("timeout")
errEmptyHashSet = errors.New("empty hash set by peer")
errPeersUnavailable = errors.New("no peers available or all peers tried for block download process")
errAlreadyInPool = errors.New("hash already in pool")
errBlockNumberOverflow = errors.New("received block which overflows")
)
type hashCheckFn func(common.Hash) bool
type getBlockFn func(common.Hash) *types.Block
type chainInsertFn func(types.Blocks) (int, error)
type hashIterFn func() (common.Hash, error)
type blockPack struct {
peerId string
blocks []*types.Block
}
type syncPack struct {
peer *peer
hash common.Hash
ignoreInitial bool
}
type hashPack struct {
peerId string
hashes []common.Hash
}
type Downloader struct {
mu sync.RWMutex
queue *queue
peers peers
activePeer string
// Callbacks
hasBlock hashCheckFn
getBlock getBlockFn
// Status
fetchingHashes int32
downloadingBlocks int32
// Channels
newPeerCh chan *peer
hashCh chan hashPack
blockCh chan blockPack
}
func New(hasBlock hashCheckFn, getBlock getBlockFn) *Downloader {
downloader := &Downloader{
queue: newqueue(),
peers: make(peers),
hasBlock: hasBlock,
getBlock: getBlock,
newPeerCh: make(chan *peer, 1),
hashCh: make(chan hashPack, 1),
blockCh: make(chan blockPack, 1),
}
return downloader
}
func (d *Downloader) Stats() (current int, max int) {
return d.queue.blockHashes.Size(), d.queue.fetchPool.Size() + d.queue.hashPool.Size()
}
func (d *Downloader) RegisterPeer(id string, hash common.Hash, getHashes hashFetcherFn, getBlocks blockFetcherFn) error {
d.mu.Lock()
defer d.mu.Unlock()
glog.V(logger.Detail).Infoln("Register peer", id)
// Create a new peer and add it to the list of known peers
peer := newPeer(id, hash, getHashes, getBlocks)
// add peer to our peer set
d.peers[id] = peer
// broadcast new peer
return nil
}
// UnregisterPeer unregister's a peer. This will prevent any action from the specified peer.
func (d *Downloader) UnregisterPeer(id string) {
d.mu.Lock()
defer d.mu.Unlock()
glog.V(logger.Detail).Infoln("Unregister peer", id)
delete(d.peers, id)
}
// SynchroniseWithPeer will select the peer and use it for synchronising. If an empty string is given
// it will use the best peer possible and synchronise if it's TD is higher than our own. If any of the
// checks fail an error will be returned. This method is synchronous
func (d *Downloader) Synchronise(id string, hash common.Hash) error {
// Make sure it's doing neither. Once done we can restart the
// downloading process if the TD is higher. For now just get on
// with whatever is going on. This prevents unecessary switching.
if d.isBusy() {
return errBusy
}
// When a synchronisation attempt is made while the queue stil
// contains items we abort the sync attempt
if d.queue.size() > 0 {
return errPendingQueue
}
// Fetch the peer using the id or throw an error if the peer couldn't be found
p := d.peers[id]
if p == nil {
return errUnknownPeer
}
// Get the hash from the peer and initiate the downloading progress.
err := d.getFromPeer(p, hash, false)
if err != nil {
return err
}
return nil
}
// Done lets the downloader know that whatever previous hashes were taken
// are processed. If the block count reaches zero and done is called
// we reset the queue for the next batch of incoming hashes and blocks.
func (d *Downloader) Done() {
d.queue.mu.Lock()
defer d.queue.mu.Unlock()
if len(d.queue.blocks) == 0 {
d.queue.resetNoTS()
}
}
// TakeBlocks takes blocks from the queue and yields them to the blockTaker handler
// it's possible it yields no blocks
func (d *Downloader) TakeBlocks() types.Blocks {
d.queue.mu.Lock()
defer d.queue.mu.Unlock()
var blocks types.Blocks
if len(d.queue.blocks) > 0 {
// Make sure the parent hash is known
if d.queue.blocks[0] != nil && !d.hasBlock(d.queue.blocks[0].ParentHash()) {
return nil
}
for _, block := range d.queue.blocks {
if block == nil {
break
}
blocks = append(blocks, block)
}
d.queue.blockOffset += len(blocks)
// delete the blocks from the slice and let them be garbage collected
// without this slice trick the blocks would stay in memory until nil
// would be assigned to d.queue.blocks
copy(d.queue.blocks, d.queue.blocks[len(blocks):])
for k, n := len(d.queue.blocks)-len(blocks), len(d.queue.blocks); k < n; k++ {
d.queue.blocks[k] = nil
}
d.queue.blocks = d.queue.blocks[:len(d.queue.blocks)-len(blocks)]
//d.queue.blocks = d.queue.blocks[len(blocks):]
if len(d.queue.blocks) == 0 {
d.queue.blocks = nil
}
}
return blocks
}
func (d *Downloader) Has(hash common.Hash) bool {
return d.queue.has(hash)
}
func (d *Downloader) getFromPeer(p *peer, hash common.Hash, ignoreInitial bool) (err error) {
d.activePeer = p.id
defer func() {
// reset on error
if err != nil {
d.queue.reset()
}
}()
glog.V(logger.Detail).Infoln("Synchronising with the network using:", p.id)
// Start the fetcher. This will block the update entirely
// interupts need to be send to the appropriate channels
// respectively.
if err = d.startFetchingHashes(p, hash, ignoreInitial); err != nil {
return err
}
// Start fetching blocks in paralel. The strategy is simple
// take any available peers, seserve a chunk for each peer available,
// let the peer deliver the chunkn and periodically check if a peer
// has timedout.
if err = d.startFetchingBlocks(p); err != nil {
return err
}
glog.V(logger.Detail).Infoln("Sync completed")
return nil
}
// XXX Make synchronous
func (d *Downloader) startFetchingHashes(p *peer, h common.Hash, ignoreInitial bool) error {
atomic.StoreInt32(&d.fetchingHashes, 1)
defer atomic.StoreInt32(&d.fetchingHashes, 0)
if d.queue.has(h) {
return errAlreadyInPool
}
glog.V(logger.Debug).Infof("Downloading hashes (%x) from %s", h[:4], p.id)
start := time.Now()
// We ignore the initial hash in some cases (e.g. we received a block without it's parent)
// In such circumstances we don't need to download the block so don't add it to the queue.
if !ignoreInitial {
// Add the hash to the queue first
d.queue.hashPool.Add(h)
}
// Get the first batch of hashes
p.getHashes(h)
var (
failureResponseTimer = time.NewTimer(hashTtl)
attemptedPeers = make(map[string]bool) // attempted peers will help with retries
activePeer = p // active peer will help determine the current active peer
hash common.Hash // common and last hash
)
attemptedPeers[p.id] = true
out:
for {
select {
case hashPack := <-d.hashCh:
// make sure the active peer is giving us the hashes
if hashPack.peerId != activePeer.id {
glog.V(logger.Debug).Infof("Received hashes from incorrect peer(%s)\n", hashPack.peerId)
break
}
failureResponseTimer.Reset(hashTtl)
var (
hashes = hashPack.hashes
done bool // determines whether we're done fetching hashes (i.e. common hash found)
)
hashSet := set.New()
for _, hash = range hashes {
if d.hasBlock(hash) || d.queue.blockHashes.Has(hash) {
glog.V(logger.Debug).Infof("Found common hash %x\n", hash[:4])
done = true
break
}
hashSet.Add(hash)
}
d.queue.put(hashSet)
// Add hashes to the chunk set
if len(hashes) == 0 { // Make sure the peer actually gave you something valid
glog.V(logger.Debug).Infof("Peer (%s) responded with empty hash set\n", activePeer.id)
d.queue.reset()
return errEmptyHashSet
} else if !done { // Check if we're done fetching
// Get the next set of hashes
activePeer.getHashes(hash)
} else { // we're done
// The offset of the queue is determined by the highest known block
var offset int
if block := d.getBlock(hash); block != nil {
offset = int(block.NumberU64() + 1)
}
// allocate proper size for the queueue
d.queue.alloc(offset, d.queue.hashPool.Size())
break out
}
case <-failureResponseTimer.C:
glog.V(logger.Debug).Infof("Peer (%s) didn't respond in time for hash request\n", p.id)
var p *peer // p will be set if a peer can be found
// Attempt to find a new peer by checking inclusion of peers best hash in our
// already fetched hash list. This can't guarantee 100% correctness but does
// a fair job. This is always either correct or false incorrect.
for id, peer := range d.peers {
if d.queue.hashPool.Has(peer.recentHash) && !attemptedPeers[id] {
p = peer
break
}
}
// if all peers have been tried, abort the process entirely or if the hash is
// the zero hash.
if p == nil || (hash == common.Hash{}) {
d.queue.reset()
return errTimeout
}
// set p to the active peer. this will invalidate any hashes that may be returned
// by our previous (delayed) peer.
activePeer = p
p.getHashes(hash)
glog.V(logger.Debug).Infof("Hash fetching switched to new peer(%s)\n", p.id)
}
}
glog.V(logger.Detail).Infof("Downloaded hashes (%d) in %v\n", d.queue.hashPool.Size(), time.Since(start))
return nil
}
func (d *Downloader) startFetchingBlocks(p *peer) error {
glog.V(logger.Detail).Infoln("Downloading", d.queue.hashPool.Size(), "block(s)")
atomic.StoreInt32(&d.downloadingBlocks, 1)
defer atomic.StoreInt32(&d.downloadingBlocks, 0)
// Defer the peer reset. This will empty the peer requested set
// and makes sure there are no lingering peers with an incorrect
// state
defer d.peers.reset()
start := time.Now()
// default ticker for re-fetching blocks everynow and then
ticker := time.NewTicker(20 * time.Millisecond)
out:
for {
select {
case blockPack := <-d.blockCh:
// If the peer was previously banned and failed to deliver it's pack
// in a reasonable time frame, ignore it's message.
if d.peers[blockPack.peerId] != nil {
err := d.queue.deliver(blockPack.peerId, blockPack.blocks)
if err != nil {
glog.V(logger.Debug).Infof("deliver failed for peer %s: %v\n", blockPack.peerId, err)
// FIXME d.UnregisterPeer(blockPack.peerId)
break
}
if glog.V(logger.Debug) {
glog.Infof("adding %d blocks from: %s\n", len(blockPack.blocks), blockPack.peerId)
}
d.peers[blockPack.peerId].promote()
d.peers.setState(blockPack.peerId, idleState)
}
case <-ticker.C:
// after removing bad peers make sure we actually have suffucient peer left to keep downlading
if len(d.peers) == 0 {
d.queue.reset()
return errNoPeers
}
// If there are unrequested hashes left start fetching
// from the available peers.
if d.queue.hashPool.Size() > 0 {
availablePeers := d.peers.get(idleState)
for _, peer := range availablePeers {
// Get a possible chunk. If nil is returned no chunk
// could be returned due to no hashes available.
chunk := d.queue.get(peer, maxBlockFetch)
if chunk == nil {
continue
}
// XXX make fetch blocking.
// Fetch the chunk and check for error. If the peer was somehow
// already fetching a chunk due to a bug, it will be returned to
// the queue
if err := peer.fetch(chunk); err != nil {
// log for tracing
glog.V(logger.Debug).Infof("peer %s received double work (state = %v)\n", peer.id, peer.state)
d.queue.put(chunk.hashes)
}
}
// make sure that we have peers available for fetching. If all peers have been tried
// and all failed throw an error
if len(d.queue.fetching) == 0 {
d.queue.reset()
return fmt.Errorf("%v peers avaialable = %d. total peers = %d. hashes needed = %d", errPeersUnavailable, len(availablePeers), len(d.peers), d.queue.hashPool.Size())
}
} else if len(d.queue.fetching) == 0 {
// When there are no more queue and no more `fetching`. We can
// safely assume we're done. Another part of the process will check
// for parent errors and will re-request anything that's missing
break out
} else {
// Check for bad peers. Bad peers may indicate a peer not responding
// to a `getBlocks` message. A timeout of 5 seconds is set. Peers
// that badly or poorly behave are removed from the peer set (not banned).
// Bad peers are excluded from the available peer set and therefor won't be
// reused. XXX We could re-introduce peers after X time.
d.queue.mu.Lock()
var badPeers []string
for pid, chunk := range d.queue.fetching {
if time.Since(chunk.itime) > blockTtl {
badPeers = append(badPeers, pid)
// remove peer as good peer from peer list
// FIXME d.UnregisterPeer(pid)
}
}
d.queue.mu.Unlock()
for _, pid := range badPeers {
// A nil chunk is delivered so that the chunk's hashes are given
// back to the queue objects. When hashes are put back in the queue
// other (decent) peers can pick them up.
// XXX We could make use of a reputation system here ranking peers
// in their performance
// 1) Time for them to respond;
// 2) Measure their speed;
// 3) Amount and availability.
d.queue.deliver(pid, nil)
if peer := d.peers[pid]; peer != nil {
peer.demote()
peer.reset()
}
}
}
}
}
glog.V(logger.Detail).Infoln("Downloaded block(s) in", time.Since(start))
return nil
}
// Deliver a chunk to the downloader. This is usually done through the BlocksMsg by
// the protocol handler.
func (d *Downloader) DeliverChunk(id string, blocks []*types.Block) {
d.blockCh <- blockPack{id, blocks}
}
func (d *Downloader) AddHashes(id string, hashes []common.Hash) error {
// make sure that the hashes that are being added are actually from the peer
// that's the current active peer. hashes that have been received from other
// peers are dropped and ignored.
if d.activePeer != id {
return fmt.Errorf("received hashes from %s while active peer is %s", id, d.activePeer)
}
if glog.V(logger.Detail) && len(hashes) != 0 {
from, to := hashes[0], hashes[len(hashes)-1]
glog.Infof("adding %d (T=%d) hashes [ %x / %x ] from: %s\n", len(hashes), d.queue.hashPool.Size(), from[:4], to[:4], id)
}
d.hashCh <- hashPack{id, hashes}
return nil
}
func (d *Downloader) isFetchingHashes() bool {
return atomic.LoadInt32(&d.fetchingHashes) == 1
}
func (d *Downloader) isDownloadingBlocks() bool {
return atomic.LoadInt32(&d.downloadingBlocks) == 1
}
func (d *Downloader) isBusy() bool {
return d.isFetchingHashes() || d.isDownloadingBlocks()
}
func (d *Downloader) IsBusy() bool {
return d.isBusy()
}
