downloader: implemented new downloader
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obscuren
328
eth/downloader/downloader.go
Normal file
328
eth/downloader/downloader.go
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@ -0,0 +1,328 @@
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package downloader
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import (
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"math"
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"math/big"
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"sync"
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"sync/atomic"
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"time"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/core/types"
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"github.com/ethereum/go-ethereum/logger"
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"github.com/ethereum/go-ethereum/logger/glog"
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"gopkg.in/fatih/set.v0"
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)
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const maxBlockFetch = 256
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type hashFetcherFn func(common.Hash) error
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type blockFetcherFn func([]common.Hash) error
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type hashCheckFn func(common.Hash) bool
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type chainInsertFn func(types.Blocks) error
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type hashIterFn func() (common.Hash, error)
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// XXX make threadsafe!!!!
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type peers map[string]*peer
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func (p peers) get(state int) []*peer {
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var peers []*peer
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for _, peer := range p {
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peer.mu.RLock()
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if peer.state == state {
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peers = append(peers, peer)
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}
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peer.mu.RUnlock()
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}
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return peers
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}
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func (p peers) setState(id string, state int) {
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if peer, exist := p[id]; exist {
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peer.mu.Lock()
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defer peer.mu.Unlock()
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peer.state = state
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}
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}
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type Downloader struct {
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queue *queue
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hasBlock hashCheckFn
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insertChain chainInsertFn
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mu sync.RWMutex
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peers peers
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currentPeer *peer
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fetchingHashes int32
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downloadingBlocks int32
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newPeerCh chan *peer
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selectPeerCh chan *peer
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HashCh chan []common.Hash
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blockCh chan blockPack
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quit chan struct{}
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}
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type blockPack struct {
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peerId string
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blocks []*types.Block
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}
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func New(hasBlock hashCheckFn, insertChain chainInsertFn) *Downloader {
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downloader := &Downloader{
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queue: newqueue(),
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peers: make(peers),
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hasBlock: hasBlock,
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insertChain: insertChain,
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newPeerCh: make(chan *peer, 1),
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selectPeerCh: make(chan *peer, 1),
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HashCh: make(chan []common.Hash, 1),
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blockCh: make(chan blockPack, 1),
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quit: make(chan struct{}),
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}
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go downloader.peerHandler()
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go downloader.update()
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return downloader
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}
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func (d *Downloader) RegisterPeer(id string, td *big.Int, hash common.Hash, getHashes hashFetcherFn, getBlocks blockFetcherFn) error {
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d.mu.Lock()
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defer d.mu.Unlock()
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glog.V(logger.Detail).Infoln("Register peer", id)
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// Create a new peer and add it to the list of known peers
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peer := newPeer(id, td, hash, getHashes, getBlocks)
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// add peer to our peer set
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d.peers[id] = peer
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// broadcast new peer
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d.newPeerCh <- peer
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return nil
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}
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func (d *Downloader) UnregisterPeer(id string) {
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d.mu.Lock()
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defer d.mu.Unlock()
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glog.V(logger.Detail).Infoln("Unregister peer", id)
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delete(d.peers, id)
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}
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func (d *Downloader) peerHandler() {
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// Fields defined here so we can reduce the amount of locking
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// that needs to be done
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var highestTd = new(big.Int)
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out:
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for {
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select {
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case newPeer := <-d.newPeerCh:
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// Check if TD of peer is higher than our current
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if newPeer.td.Cmp(highestTd) > 0 {
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glog.V(logger.Detail).Infoln("New peer with highest TD =", newPeer.td)
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highestTd.Set(newPeer.td)
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// select the peer for downloading
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d.selectPeerCh <- newPeer
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}
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case <-d.quit:
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break out
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}
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}
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}
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func (d *Downloader) update() {
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out:
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for {
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select {
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case selectedPeer := <-d.selectPeerCh:
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// Make sure it's doing neither. Once done we can restart the
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// downloading process if the TD is higher. For now just get on
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// with whatever is going on. This prevents unecessary switching.
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if !(d.isFetchingHashes() || d.isDownloadingBlocks()) {
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glog.V(logger.Detail).Infoln("Selected new peer", selectedPeer.id)
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// Start the fetcher. This will block the update entirely
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// interupts need to be send to the appropriate channels
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// respectively.
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if err := d.startFetchingHashes(selectedPeer); err != nil {
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// handle error
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glog.V(logger.Debug).Infoln("Error fetching hashes:", err)
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// Reset
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break
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}
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// Start fetching blocks in paralel. The strategy is simple
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// take any available peers, seserve a chunk for each peer available,
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// let the peer deliver the chunkn and periodically check if a peer
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// has timedout. When done downloading, process blocks.
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if err := d.startFetchingBlocks(selectedPeer); err != nil {
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glog.V(logger.Debug).Infoln("Error downloading blocks:", err)
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// reset
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break
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}
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// XXX this will move when optimised
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// Sort the blocks by number. This bit needs much improvement. Right now
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// it assumes full honesty form peers (i.e. it's not checked when the blocks
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// link). We should at least check whihc queue match. This code could move
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// to a seperate goroutine where it periodically checks for linked pieces.
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types.BlockBy(types.Number).Sort(d.queue.blocks)
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blocks := d.queue.blocks
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glog.V(logger.Debug).Infoln("Inserting chain with", len(blocks), "blocks")
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// Loop untill we're out of queue
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for len(blocks) != 0 {
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max := int(math.Min(float64(len(blocks)), 256))
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// TODO check for parent error. When there's a parent error we should stop
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// processing and start requesting the `block.hash` so that it's parent and
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// grandparents can be requested and queued.
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d.insertChain(blocks[:max])
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blocks = blocks[max:]
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}
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}
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case <-d.quit:
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break out
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}
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}
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}
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func (d *Downloader) startFetchingHashes(p *peer) error {
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glog.V(logger.Debug).Infoln("Downloading hashes")
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start := time.Now()
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// Get the first batch of hashes
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p.getHashes(p.recentHash)
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atomic.StoreInt32(&d.fetchingHashes, 1)
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out:
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for {
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select {
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case hashes := <-d.HashCh:
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var done bool // determines whether we're done fetching hashes (i.e. common hash found)
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hashSet := set.New()
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for _, hash := range hashes {
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if d.hasBlock(hash) {
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glog.V(logger.Debug).Infof("Found common hash %x\n", hash)
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done = true
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break
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}
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hashSet.Add(hash)
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}
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d.queue.put(hashSet)
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// Add hashes to the chunk set
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// Check if we're done fetching
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if !done {
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//fmt.Println("re-fetch. current =", d.queue.hashPool.Size())
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// Get the next set of hashes
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p.getHashes(hashes[len(hashes)-1])
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atomic.StoreInt32(&d.fetchingHashes, 1)
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} else {
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atomic.StoreInt32(&d.fetchingHashes, 0)
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break out
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}
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}
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}
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glog.V(logger.Detail).Infoln("Download hashes: done. Took", time.Since(start))
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return nil
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}
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func (d *Downloader) DeliverBlocks(id string, block []*types.Block) {
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d.blockCh <- blockPack{id, block}
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}
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func (d *Downloader) startFetchingBlocks(p *peer) error {
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glog.V(logger.Detail).Infoln("Downloading", d.queue.hashPool.Size(), "blocks")
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atomic.StoreInt32(&d.downloadingBlocks, 1)
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start := time.Now()
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// default ticker for re-fetching blocks everynow and then
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ticker := time.NewTicker(20 * time.Millisecond)
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out:
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for {
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select {
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case blockPack := <-d.blockCh:
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//fmt.Println("get for", blockPack.peerId)
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d.queue.deliver(blockPack.peerId, blockPack.blocks)
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d.peers.setState(blockPack.peerId, idleState)
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case <-ticker.C:
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// If there are unrequested hashes left start fetching
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// from the available peers.
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if d.queue.hashPool.Size() > 0 {
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availablePeers := d.peers.get(idleState)
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for _, peer := range availablePeers {
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// Get a possible chunk. If nil is returned no chunk
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// could be returned due to no hashes available.
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chunk := d.queue.get(peer, maxBlockFetch)
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if chunk != nil {
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//fmt.Println("fetching for", peer.id)
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// Fetch the chunk.
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peer.fetch(chunk)
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}
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}
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atomic.StoreInt32(&d.downloadingBlocks, 1)
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} else if len(d.queue.fetching) == 0 {
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// Whene there are no more queue and no more `fetching`. We can
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// safely assume we're done. Another part of the process will check
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// for parent errors and will re-request anything that's missing
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atomic.StoreInt32(&d.downloadingBlocks, 0)
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// Break out so that we can process with processing blocks
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break out
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} else {
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// Check for bad peers. Bad peers may indicate a peer not responding
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// to a `getBlocks` message. A timeout of 5 seconds is set. Peers
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// that badly or poorly behave are removed from the peer set (not banned).
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// Bad peers are excluded from the available peer set and therefor won't be
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// reused. XXX We could re-introduce peers after X time.
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d.queue.mu.Lock()
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var badPeers []string
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for pid, chunk := range d.queue.fetching {
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if time.Since(chunk.itime) > 5*time.Second {
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badPeers = append(badPeers, pid)
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// remove peer as good peer from peer list
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d.UnregisterPeer(pid)
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}
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}
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d.queue.mu.Unlock()
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for _, pid := range badPeers {
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// A nil chunk is delivered so that the chunk's hashes are given
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// back to the queue objects. When hashes are put back in the queue
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// other (decent) peers can pick them up.
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// XXX We could make use of a reputation system here ranking peers
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// in their performance
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// 1) Time for them to respond;
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// 2) Measure their speed;
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// 3) Amount and availability.
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d.queue.deliver(pid, nil)
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}
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}
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//fmt.Println(d.queue.hashPool.Size(), len(d.queue.fetching))
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}
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}
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glog.V(logger.Detail).Infoln("Download blocks: done. Took", time.Since(start))
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return nil
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}
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func (d *Downloader) isFetchingHashes() bool {
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return atomic.LoadInt32(&d.fetchingHashes) == 1
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}
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func (d *Downloader) isDownloadingBlocks() bool {
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return atomic.LoadInt32(&d.downloadingBlocks) == 1
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}
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