downloader: implemented new downloader

1 files changed, 328 insertions, 0 deletions

diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
new file mode 100644
index 000000000..1b9b7d01b
--- /dev/null
+++ b/eth/downloader/downloader.go
@@ -0,0 +1,328 @@
+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.
+						peer.fetch(chunk)
+					}
+				}
+				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
+}