package downloader import ( "errors" "fmt" "math" "math/big" "sync" "sync/atomic" "time" "github.com/ethereum/go-ethereum/common" "github.com/ethereum/go-ethereum/core" "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") 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") ) type hashCheckFn func(common.Hash) bool 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 Downloader struct { mu sync.RWMutex queue *queue peers peers activePeer string // Callbacks hasBlock hashCheckFn insertChain chainInsertFn // Status fetchingHashes int32 downloadingBlocks int32 processingBlocks int32 // Channels newPeerCh chan *peer hashCh chan []common.Hash blockCh chan blockPack } func New(hasBlock hashCheckFn, insertChain chainInsertFn) *Downloader { downloader := &Downloader{ queue: newqueue(), peers: make(peers), hasBlock: hasBlock, insertChain: insertChain, newPeerCh: make(chan *peer, 1), hashCh: make(chan []common.Hash, 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 } // 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 d.process(p) } func (d *Downloader) getFromPeer(p *peer, hash common.Hash, ignoreInitial bool) error { d.activePeer = p.id 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 { // handle error glog.V(logger.Debug).Infoln("Error fetching hashes:", err) // XXX Reset 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. When done downloading, process blocks. if err := d.startFetchingBlocks(p); err != nil { glog.V(logger.Debug).Infoln("Error downloading blocks:", err) // XXX reset return err } glog.V(logger.Detail).Infoln("Sync completed") return nil } // XXX Make synchronous func (d *Downloader) startFetchingHashes(p *peer, hash common.Hash, ignoreInitial bool) error { atomic.StoreInt32(&d.fetchingHashes, 1) defer atomic.StoreInt32(&d.fetchingHashes, 0) glog.V(logger.Debug).Infof("Downloading hashes (%x) from %s", hash.Bytes()[: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(hash) } // Get the first batch of hashes p.getHashes(hash) failureResponseTimer := time.NewTimer(hashTtl) out: for { select { case hashes := <-d.hashCh: failureResponseTimer.Reset(hashTtl) 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[: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", p.id) d.queue.reset() return errEmptyHashSet } else if !done { // Check if we're done fetching // Get the next set of hashes p.getHashes(hashes[len(hashes)-1]) } else { // we're done break out } case <-failureResponseTimer.C: glog.V(logger.Debug).Infof("Peer (%s) didn't respond in time for hash request\n", p.id) // TODO instead of reseting the queue select a new peer from which we can start downloading hashes. // 1. check for peer's best hash to be included in the current hash set; // 2. resume from last point (hashes[len(hashes)-1]) using the newly selected peer. d.queue.reset() return errTimeout } } 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 { d.peers[blockPack.peerId].promote() 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 { 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 //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 <- hashes return nil } // Add an (unrequested) block to the downloader. This is usually done through the // NewBlockMsg by the protocol handler. // Adding blocks is done synchronously. if there are missing blocks, blocks will be // fetched first. If the downloader is busy or if some other processed failed an error // will be returned. func (d *Downloader) AddBlock(id string, block *types.Block, td *big.Int) error { hash := block.Hash() if d.hasBlock(hash) { return fmt.Errorf("known block %x", hash.Bytes()[:4]) } peer := d.peers.getPeer(id) // if the peer is in our healthy list of peers; update the td // and add the block. Otherwise just ignore it if peer == nil { glog.V(logger.Detail).Infof("Ignored block from bad peer %s\n", id) return ErrBadPeer } peer.mu.Lock() peer.recentHash = block.Hash() peer.mu.Unlock() peer.promote() glog.V(logger.Detail).Infoln("Inserting new block from:", id) d.queue.addBlock(id, block) // if neither go ahead to process if d.isBusy() { return errBusy } // Check if the parent of the received block is known. // If the block is not know, request it otherwise, request. phash := block.ParentHash() if !d.hasBlock(phash) { glog.V(logger.Detail).Infof("Missing parent %x, requires fetching\n", phash.Bytes()[:4]) // Get the missing hashes from the peer (synchronously) err := d.getFromPeer(peer, peer.recentHash, true) if err != nil { return err } } return d.process(peer) } func (d *Downloader) process(peer *peer) error { atomic.StoreInt32(&d.processingBlocks, 1) defer atomic.StoreInt32(&d.processingBlocks, 0) // 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) if len(d.queue.blocks) == 0 { return nil } var blocks = d.queue.blocks glog.V(logger.Debug).Infof("Inserting chain with %d blocks (#%v - #%v)\n", len(blocks), blocks[0].Number(), blocks[len(blocks)-1].Number()) // Loop untill we're out of blocks 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. var i int i, err := d.insertChain(blocks[:max]) if err != nil && core.IsParentErr(err) { // Ignore the missing blocks. Handler should take care of anything that's missing. glog.V(logger.Debug).Infof("Ignored block with missing parent (%d)\n", i) blocks = blocks[i+1:] continue } else if err != nil { // immediatly unregister the false peer but do not disconnect d.UnregisterPeer(d.activePeer) // Reset chain completely. This needs much, much improvement. // instead: check all blocks leading down to this block false block and remove it d.queue.blocks = nil return ErrBadPeer } // 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(blocks, blocks[max:]) for k, n := len(blocks)-max, len(blocks); k < n; k++ { blocks[k] = nil } blocks = blocks[:len(blocks)-max] } if len(blocks) == 0 { d.queue.blocks = nil } else { d.queue.blocks = blocks } 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) isProcessing() bool { return atomic.LoadInt32(&d.processingBlocks) == 1 } func (d *Downloader) isBusy() bool { return d.isFetchingHashes() || d.isDownloadingBlocks() || d.isProcessing() } func (d *Downloader) IsBusy() bool { return d.isBusy() }