package downloader
import (
"math"
"math/big"
"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
type hashFetcherFn func(common.Hash) error
type blockFetcherFn func([]common.Hash) error
type hashCheckFn func(common.Hash) bool
type chainInsertFn func(types.Blocks) error
type hashIterFn func() (common.Hash, error)
// XXX make threadsafe!!!!
type peers map[string]*peer
func (p peers) get(state int) []*peer {
var peers []*peer
for _, peer := range p {
peer.mu.RLock()
if peer.state == state {
peers = append(peers, peer)
}
peer.mu.RUnlock()
}
return peers
}
func (p peers) setState(id string, state int) {
if peer, exist := p[id]; exist {
peer.mu.Lock()
defer peer.mu.Unlock()
peer.state = state
}
}
type Downloader struct {
queue *queue
hasBlock hashCheckFn
insertChain chainInsertFn
mu sync.RWMutex
peers peers
currentPeer *peer
fetchingHashes int32
downloadingBlocks int32
newPeerCh chan *peer
selectPeerCh chan *peer
HashCh chan []common.Hash
blockCh chan blockPack
quit chan struct{}
}
type blockPack struct {
peerId string
blocks []*types.Block
}
func New(hasBlock hashCheckFn, insertChain chainInsertFn) *Downloader {
downloader := &Downloader{
queue: newqueue(),
peers: make(peers),
hasBlock: hasBlock,
insertChain: insertChain,
newPeerCh: make(chan *peer, 1),
selectPeerCh: make(chan *peer, 1),
HashCh: make(chan []common.Hash, 1),
blockCh: make(chan blockPack, 1),
quit: make(chan struct{}),
}
go downloader.peerHandler()
go downloader.update()
return downloader
}
func (d *Downloader) RegisterPeer(id string, td *big.Int, 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, td, hash, getHashes, getBlocks)
// add peer to our peer set
d.peers[id] = peer
// broadcast new peer
d.newPeerCh <- peer
return nil
}
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)
}
func (d *Downloader) peerHandler() {
// Fields defined here so we can reduce the amount of locking
// that needs to be done
var highestTd = new(big.Int)
out:
for {
select {
case newPeer := <-d.newPeerCh:
// Check if TD of peer is higher than our current
if newPeer.td.Cmp(highestTd) > 0 {
glog.V(logger.Detail).Infoln("New peer with highest TD =", newPeer.td)
highestTd.Set(newPeer.td)
// select the peer for downloading
d.selectPeerCh <- newPeer
}
case <-d.quit:
break out
}
}
}
func (d *Downloader) update() {
out:
for {
select {
case selectedPeer := <-d.selectPeerCh:
// 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.isFetchingHashes() || d.isDownloadingBlocks()) {
glog.V(logger.Detail).Infoln("Selected new peer", selectedPeer.id)
// Start the fetcher. This will block the update entirely
// interupts need to be send to the appropriate channels
// respectively.
if err := d.startFetchingHashes(selectedPeer); err != nil {
// handle error
glog.V(logger.Debug).Infoln("Error fetching hashes:", err)
// Reset
break
}
// 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. When done downloading, process blocks.
if err := d.startFetchingBlocks(selectedPeer); err != nil {
glog.V(logger.Debug).Infoln("Error downloading blocks:", err)
// reset
break
}
// XXX this will move when optimised
// Sort the blocks by number. This bit needs much improvement. Right now
// it assumes full honesty form peers (i.e. it's not checked when the blocks
// link). We should at least check whihc queue match. This code could move
// to a seperate goroutine where it periodically checks for linked pieces.
types.BlockBy(types.Number).Sort(d.queue.blocks)
blocks := d.queue.blocks
glog.V(logger.Debug).Infoln("Inserting chain with", len(blocks), "blocks")
// Loop untill we're out of queue
for len(blocks) != 0 {
max := int(math.Min(float64(len(blocks)), 256))
// TODO check for parent error. When there's a parent error we should stop
// processing and start requesting the `block.hash` so that it's parent and
// grandparents can be requested and queued.
d.insertChain(blocks[:max])
blocks = blocks[max:]
}
}
case <-d.quit:
break out
}
}
}
func (d *Downloader) startFetchingHashes(p *peer) error {
glog.V(logger.Debug).Infoln("Downloading hashes")
start := time.Now()
// Get the first batch of hashes
p.getHashes(p.recentHash)
atomic.StoreInt32(&d.fetchingHashes, 1)
out:
for {
select {
case hashes := <-d.HashCh:
var 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) {
glog.V(logger.Debug).Infof("Found common hash %x\n", hash)
done = true
break
}
hashSet.Add(hash)
}
d.queue.put(hashSet)
// Add hashes to the chunk set
// Check if we're done fetching
if !done {
//fmt.Println("re-fetch. current =", d.queue.hashPool.Size())
// Get the next set of hashes
p.getHashes(hashes[len(hashes)-1])
atomic.StoreInt32(&d.fetchingHashes, 1)
} else {
atomic.StoreInt32(&d.fetchingHashes, 0)
break out
}
}
}
glog.V(logger.Detail).Infoln("Download hashes: done. Took", time.Since(start))
return nil
}
func (d *Downloader) DeliverBlocks(id string, block []*types.Block) {
d.blockCh <- blockPack{id, block}
}
func (d *Downloader) startFetchingBlocks(p *peer) error {
glog.V(logger.Detail).Infoln("Downloading", d.queue.hashPool.Size(), "blocks")
atomic.StoreInt32(&d.downloadingBlocks, 1)
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:
//fmt.Println("get for", blockPack.peerId)
d.queue.deliver(blockPack.peerId, blockPack.blocks)
d.peers.setState(blockPack.peerId, idleState)
case <-ticker.C:
// 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 {
//fmt.Println("fetching for", peer.id)
// 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)
}
}
}
atomic.StoreInt32(&d.downloadingBlocks, 1)
} else if len(d.queue.fetching) == 0 {
// Whene 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
atomic.StoreInt32(&d.downloadingBlocks, 0)
// Break out so that we can process with processing blocks
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) > 5*time.Second {
badPeers = append(badPeers, pid)
// remove peer as good peer from peer list
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)
}
}
//fmt.Println(d.queue.hashPool.Size(), len(d.queue.fetching))
}
}
glog.V(logger.Detail).Infoln("Download blocks: done. Took", time.Since(start))
return nil
}
func (d *Downloader) isFetchingHashes() bool {
return atomic.LoadInt32(&d.fetchingHashes) == 1
}
func (d *Downloader) isDownloadingBlocks() bool {
return atomic.LoadInt32(&d.downloadingBlocks) == 1
}
