plugeth/eth/downloader/downloader.go

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// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
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//
// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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// Package downloader contains the manual full chain synchronisation.
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package downloader
import (
"errors"
"math"
"math/big"
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"sync"
"sync/atomic"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/event"
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"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/logger/glog"
)
const (
eth61 = 61 // Constant to check for old protocol support
eth62 = 62 // Constant to check for new protocol support
)
var (
MaxHashFetch = 512 // Amount of hashes to be fetched per retrieval request
MaxBlockFetch = 128 // Amount of blocks to be fetched per retrieval request
MaxHeaderFetch = 192 // Amount of block headers to be fetched per retrieval request
MaxBodyFetch = 128 // Amount of block bodies to be fetched per retrieval request
MaxStateFetch = 384 // Amount of node state values to allow fetching per request
MaxReceiptsFetch = 384 // Amount of transaction receipts to allow fetching per request
hashTTL = 5 * time.Second // [eth/61] Time it takes for a hash request to time out
blockSoftTTL = 3 * time.Second // [eth/61] Request completion threshold for increasing or decreasing a peer's bandwidth
blockHardTTL = 3 * blockSoftTTL // [eth/61] Maximum time allowance before a block request is considered expired
headerTTL = 5 * time.Second // [eth/62] Time it takes for a header request to time out
bodySoftTTL = 3 * time.Second // [eth/62] Request completion threshold for increasing or decreasing a peer's bandwidth
bodyHardTTL = 3 * bodySoftTTL // [eth/62] Maximum time allowance before a block body request is considered expired
maxQueuedHashes = 256 * 1024 // [eth/61] Maximum number of hashes to queue for import (DOS protection)
maxQueuedHeaders = 256 * 1024 // [eth/62] Maximum number of headers to queue for import (DOS protection)
maxBlockProcess = 256 // Number of blocks to import at once into the chain
)
var (
errBusy = errors.New("busy")
errUnknownPeer = errors.New("peer is unknown or unhealthy")
errBadPeer = errors.New("action from bad peer ignored")
errStallingPeer = errors.New("peer is stalling")
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")
errEmptyHeaderSet = errors.New("empty header set by peer")
errPeersUnavailable = errors.New("no peers available or all peers tried for block download process")
errAlreadyInPool = errors.New("hash already in pool")
errInvalidChain = errors.New("retrieved hash chain is invalid")
errInvalidBody = errors.New("retrieved block body is invalid")
errCancelHashFetch = errors.New("hash fetching canceled (requested)")
errCancelBlockFetch = errors.New("block downloading canceled (requested)")
errCancelHeaderFetch = errors.New("block header fetching canceled (requested)")
errCancelBodyFetch = errors.New("block body downloading canceled (requested)")
errNoSyncActive = errors.New("no sync active")
)
// hashCheckFn is a callback type for verifying a hash's presence in the local chain.
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type hashCheckFn func(common.Hash) bool
// blockRetrievalFn is a callback type for retrieving a block from the local chain.
type blockRetrievalFn func(common.Hash) *types.Block
// headRetrievalFn is a callback type for retrieving the head block from the local chain.
type headRetrievalFn func() *types.Block
// chainInsertFn is a callback type to insert a batch of blocks into the local chain.
type chainInsertFn func(types.Blocks) (int, error)
// peerDropFn is a callback type for dropping a peer detected as malicious.
type peerDropFn func(id string)
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// hashPack is a batch of block hashes returned by a peer (eth/61).
type hashPack struct {
peerId string
hashes []common.Hash
}
// blockPack is a batch of blocks returned by a peer (eth/61).
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type blockPack struct {
peerId string
blocks []*types.Block
}
// headerPack is a batch of block headers returned by a peer.
type headerPack struct {
peerId string
headers []*types.Header
}
// bodyPack is a batch of block bodies returned by a peer.
type bodyPack struct {
peerId string
transactions [][]*types.Transaction
uncles [][]*types.Header
}
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type Downloader struct {
mux *event.TypeMux
queue *queue // Scheduler for selecting the hashes to download
peers *peerSet // Set of active peers from which download can proceed
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interrupt int32 // Atomic boolean to signal termination
// Statistics
importStart time.Time // Instance when the last blocks were taken from the cache
importQueue []*Block // Previously taken blocks to check import progress
importDone int // Number of taken blocks already imported from the last batch
importLock sync.Mutex
// Callbacks
hasBlock hashCheckFn // Checks if a block is present in the chain
getBlock blockRetrievalFn // Retrieves a block from the chain
headBlock headRetrievalFn // Retrieves the head block from the chain
insertChain chainInsertFn // Injects a batch of blocks into the chain
dropPeer peerDropFn // Drops a peer for misbehaving
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// Status
synchroniseMock func(id string, hash common.Hash) error // Replacement for synchronise during testing
synchronising int32
processing int32
notified int32
// Channels
newPeerCh chan *peer
hashCh chan hashPack // [eth/61] Channel receiving inbound hashes
blockCh chan blockPack // [eth/61] Channel receiving inbound blocks
headerCh chan headerPack // [eth/62] Channel receiving inbound block headers
bodyCh chan bodyPack // [eth/62] Channel receiving inbound block bodies
processCh chan bool // Channel to signal the block fetcher of new or finished work
cancelCh chan struct{} // Channel to cancel mid-flight syncs
cancelLock sync.RWMutex // Lock to protect the cancel channel in delivers
// Testing hooks
bodyFetchHook func([]*types.Header) // Method to call upon starting a block body fetch
chainInsertHook func([]*Block) // Method to call upon inserting a chain of blocks (possibly in multiple invocations)
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}
// Block is an origin-tagged blockchain block.
type Block struct {
RawBlock *types.Block
OriginPeer string
}
// New creates a new downloader to fetch hashes and blocks from remote peers.
func New(mux *event.TypeMux, hasBlock hashCheckFn, getBlock blockRetrievalFn, headBlock headRetrievalFn, insertChain chainInsertFn, dropPeer peerDropFn) *Downloader {
return &Downloader{
mux: mux,
queue: newQueue(),
peers: newPeerSet(),
hasBlock: hasBlock,
getBlock: getBlock,
headBlock: headBlock,
insertChain: insertChain,
dropPeer: dropPeer,
newPeerCh: make(chan *peer, 1),
hashCh: make(chan hashPack, 1),
blockCh: make(chan blockPack, 1),
headerCh: make(chan headerPack, 1),
bodyCh: make(chan bodyPack, 1),
processCh: make(chan bool, 1),
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}
}
// Stats retrieves the current status of the downloader.
func (d *Downloader) Stats() (pending int, cached int, importing int, estimate time.Duration) {
// Fetch the download status
pending, cached = d.queue.Size()
// Figure out the import progress
d.importLock.Lock()
defer d.importLock.Unlock()
for len(d.importQueue) > 0 && d.hasBlock(d.importQueue[0].RawBlock.Hash()) {
d.importQueue = d.importQueue[1:]
d.importDone++
}
importing = len(d.importQueue)
// Make an estimate on the total sync
estimate = 0
if d.importDone > 0 {
estimate = time.Since(d.importStart) / time.Duration(d.importDone) * time.Duration(pending+cached+importing)
}
return
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}
// Synchronising returns whether the downloader is currently retrieving blocks.
func (d *Downloader) Synchronising() bool {
return atomic.LoadInt32(&d.synchronising) > 0
}
// RegisterPeer injects a new download peer into the set of block source to be
// used for fetching hashes and blocks from.
func (d *Downloader) RegisterPeer(id string, version int, head common.Hash,
getRelHashes relativeHashFetcherFn, getAbsHashes absoluteHashFetcherFn, getBlocks blockFetcherFn, // eth/61 callbacks, remove when upgrading
getRelHeaders relativeHeaderFetcherFn, getAbsHeaders absoluteHeaderFetcherFn, getBlockBodies blockBodyFetcherFn) error {
glog.V(logger.Detail).Infoln("Registering peer", id)
if err := d.peers.Register(newPeer(id, version, head, getRelHashes, getAbsHashes, getBlocks, getRelHeaders, getAbsHeaders, getBlockBodies)); err != nil {
glog.V(logger.Error).Infoln("Register failed:", err)
return err
}
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return nil
}
// UnregisterPeer remove a peer from the known list, preventing any action from
// the specified peer.
func (d *Downloader) UnregisterPeer(id string) error {
glog.V(logger.Detail).Infoln("Unregistering peer", id)
if err := d.peers.Unregister(id); err != nil {
glog.V(logger.Error).Infoln("Unregister failed:", err)
return err
}
return nil
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}
// Synchronise tries to sync up our local block chain with a remote peer, both
// adding various sanity checks as well as wrapping it with various log entries.
func (d *Downloader) Synchronise(id string, head common.Hash, td *big.Int) {
glog.V(logger.Detail).Infof("Attempting synchronisation: %v, head [%x…], TD %v", id, head[:4], td)
switch err := d.synchronise(id, head, td); err {
case nil:
glog.V(logger.Detail).Infof("Synchronisation completed")
case errBusy:
glog.V(logger.Detail).Infof("Synchronisation already in progress")
case errTimeout, errBadPeer, errStallingPeer, errEmptyHashSet, errEmptyHeaderSet, errPeersUnavailable, errInvalidChain:
glog.V(logger.Debug).Infof("Removing peer %v: %v", id, err)
d.dropPeer(id)
case errPendingQueue:
glog.V(logger.Debug).Infoln("Synchronisation aborted:", err)
default:
glog.V(logger.Warn).Infof("Synchronisation failed: %v", err)
}
}
// synchronise will select the peer and use it for synchronising. If an empty string is given
// it will use the best peer possible and synchronize 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, td *big.Int) error {
// Mock out the synchonisation if testing
if d.synchroniseMock != nil {
return d.synchroniseMock(id, hash)
}
// Make sure only one goroutine is ever allowed past this point at once
if !atomic.CompareAndSwapInt32(&d.synchronising, 0, 1) {
return errBusy
}
defer atomic.StoreInt32(&d.synchronising, 0)
// Post a user notification of the sync (only once per session)
if atomic.CompareAndSwapInt32(&d.notified, 0, 1) {
glog.V(logger.Info).Infoln("Block synchronisation started")
}
// Abort if the queue still contains some leftover data
if _, cached := d.queue.Size(); cached > 0 && d.queue.GetHeadBlock() != nil {
return errPendingQueue
}
// Reset the queue and peer set to clean any internal leftover state
d.queue.Reset()
d.peers.Reset()
// Create cancel channel for aborting mid-flight
d.cancelLock.Lock()
d.cancelCh = make(chan struct{})
d.cancelLock.Unlock()
// Retrieve the origin peer and initiate the downloading process
p := d.peers.Peer(id)
if p == nil {
return errUnknownPeer
}
return d.syncWithPeer(p, hash, td)
}
// Has checks if the downloader knows about a particular hash, meaning that its
// either already downloaded of pending retrieval.
func (d *Downloader) Has(hash common.Hash) bool {
return d.queue.Has(hash)
}
// syncWithPeer starts a block synchronization based on the hash chain from the
// specified peer and head hash.
func (d *Downloader) syncWithPeer(p *peer, hash common.Hash, td *big.Int) (err error) {
d.mux.Post(StartEvent{})
defer func() {
// reset on error
if err != nil {
d.cancel()
d.mux.Post(FailedEvent{err})
} else {
d.mux.Post(DoneEvent{})
}
}()
glog.V(logger.Debug).Infof("Synchronising with the network using: %s [eth/%d]", p.id, p.version)
defer glog.V(logger.Debug).Infof("Synchronisation terminated")
switch {
case p.version == eth61:
// Old eth/61, use forward, concurrent hash and block retrieval algorithm
number, err := d.findAncestor61(p)
if err != nil {
return err
}
errc := make(chan error, 2)
go func() { errc <- d.fetchHashes61(p, td, number+1) }()
go func() { errc <- d.fetchBlocks61(number + 1) }()
// If any fetcher fails, cancel the other
if err := <-errc; err != nil {
d.cancel()
<-errc
return err
}
return <-errc
case p.version >= eth62:
// New eth/62, use forward, concurrent header and block body retrieval algorithm
number, err := d.findAncestor(p)
if err != nil {
return err
}
errc := make(chan error, 2)
go func() { errc <- d.fetchHeaders(p, td, number+1) }()
go func() { errc <- d.fetchBodies(number + 1) }()
// If any fetcher fails, cancel the other
if err := <-errc; err != nil {
d.cancel()
<-errc
return err
}
return <-errc
default:
// Something very wrong, stop right here
glog.V(logger.Error).Infof("Unsupported eth protocol: %d", p.version)
return errBadPeer
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}
return nil
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}
// cancel cancels all of the operations and resets the queue. It returns true
// if the cancel operation was completed.
func (d *Downloader) cancel() {
// Close the current cancel channel
d.cancelLock.Lock()
if d.cancelCh != nil {
select {
case <-d.cancelCh:
// Channel was already closed
default:
close(d.cancelCh)
}
}
d.cancelLock.Unlock()
// Reset the queue
d.queue.Reset()
}
// Terminate interrupts the downloader, canceling all pending operations.
func (d *Downloader) Terminate() {
atomic.StoreInt32(&d.interrupt, 1)
d.cancel()
}
// findAncestor61 tries to locate the common ancestor block of the local chain and
// a remote peers blockchain. In the general case when our node was in sync and
// on the correct chain, checking the top N blocks should already get us a match.
// In the rare scenario when we ended up on a long reorganization (i.e. none of
// the head blocks match), we do a binary search to find the common ancestor.
func (d *Downloader) findAncestor61(p *peer) (uint64, error) {
glog.V(logger.Debug).Infof("%v: looking for common ancestor", p)
// Request out head blocks to short circuit ancestor location
head := d.headBlock().NumberU64()
from := int64(head) - int64(MaxHashFetch) + 1
if from < 0 {
from = 0
}
go p.getAbsHashes(uint64(from), MaxHashFetch)
// Wait for the remote response to the head fetch
number, hash := uint64(0), common.Hash{}
timeout := time.After(hashTTL)
for finished := false; !finished; {
select {
case <-d.cancelCh:
return 0, errCancelHashFetch
case hashPack := <-d.hashCh:
// Discard anything not from the origin peer
if hashPack.peerId != p.id {
glog.V(logger.Debug).Infof("Received hashes from incorrect peer(%s)", hashPack.peerId)
break
}
// Make sure the peer actually gave something valid
hashes := hashPack.hashes
if len(hashes) == 0 {
glog.V(logger.Debug).Infof("%v: empty head hash set", p)
return 0, errEmptyHashSet
}
// Check if a common ancestor was found
finished = true
for i := len(hashes) - 1; i >= 0; i-- {
if d.hasBlock(hashes[i]) {
number, hash = uint64(from)+uint64(i), hashes[i]
break
}
}
case <-d.blockCh:
// Out of bounds blocks received, ignore them
case <-d.headerCh:
// Out of bounds eth/62 block headers received, ignore them
case <-d.bodyCh:
// Out of bounds eth/62 block bodies received, ignore them
case <-timeout:
glog.V(logger.Debug).Infof("%v: head hash timeout", p)
return 0, errTimeout
}
}
// If the head fetch already found an ancestor, return
if !common.EmptyHash(hash) {
glog.V(logger.Debug).Infof("%v: common ancestor: #%d [%x…]", p, number, hash[:4])
return number, nil
}
// Ancestor not found, we need to binary search over our chain
start, end := uint64(0), head
for start+1 < end {
// Split our chain interval in two, and request the hash to cross check
check := (start + end) / 2
timeout := time.After(hashTTL)
go p.getAbsHashes(uint64(check), 1)
// Wait until a reply arrives to this request
for arrived := false; !arrived; {
select {
case <-d.cancelCh:
return 0, errCancelHashFetch
case hashPack := <-d.hashCh:
// Discard anything not from the origin peer
if hashPack.peerId != p.id {
glog.V(logger.Debug).Infof("Received hashes from incorrect peer(%s)", hashPack.peerId)
break
}
// Make sure the peer actually gave something valid
hashes := hashPack.hashes
if len(hashes) != 1 {
glog.V(logger.Debug).Infof("%v: invalid search hash set (%d)", p, len(hashes))
return 0, errBadPeer
}
arrived = true
// Modify the search interval based on the response
block := d.getBlock(hashes[0])
if block == nil {
end = check
break
}
if block.NumberU64() != check {
glog.V(logger.Debug).Infof("%v: non requested hash #%d [%x…], instead of #%d", p, block.NumberU64(), block.Hash().Bytes()[:4], check)
return 0, errBadPeer
}
start = check
case <-d.blockCh:
// Out of bounds blocks received, ignore them
case <-d.headerCh:
// Out of bounds eth/62 block headers received, ignore them
case <-d.bodyCh:
// Out of bounds eth/62 block bodies received, ignore them
case <-timeout:
glog.V(logger.Debug).Infof("%v: search hash timeout", p)
return 0, errTimeout
}
}
}
return start, nil
}
// fetchHashes61 keeps retrieving hashes from the requested number, until no more
// are returned, potentially throttling on the way.
func (d *Downloader) fetchHashes61(p *peer, td *big.Int, from uint64) error {
glog.V(logger.Debug).Infof("%v: downloading hashes from #%d", p, from)
// Create a timeout timer, and the associated hash fetcher
request := time.Now() // time of the last fetch request
timeout := time.NewTimer(0) // timer to dump a non-responsive active peer
<-timeout.C // timeout channel should be initially empty
defer timeout.Stop()
getHashes := func(from uint64) {
glog.V(logger.Detail).Infof("%v: fetching %d hashes from #%d", p, MaxHashFetch, from)
go p.getAbsHashes(from, MaxHashFetch)
request = time.Now()
timeout.Reset(hashTTL)
}
// Start pulling hashes, until all are exhausted
getHashes(from)
gotHashes := false
for {
select {
case <-d.cancelCh:
return errCancelHashFetch
case <-d.headerCh:
// Out of bounds eth/62 block headers received, ignore them
case <-d.bodyCh:
// Out of bounds eth/62 block bodies received, ignore them
case hashPack := <-d.hashCh:
// Make sure the active peer is giving us the hashes
if hashPack.peerId != p.id {
glog.V(logger.Debug).Infof("Received hashes from incorrect peer(%s)", hashPack.peerId)
break
}
hashReqTimer.UpdateSince(request)
timeout.Stop()
// If no more hashes are inbound, notify the block fetcher and return
if len(hashPack.hashes) == 0 {
glog.V(logger.Debug).Infof("%v: no available hashes", p)
select {
case d.processCh <- false:
case <-d.cancelCh:
}
// If no hashes were retrieved at all, the peer violated it's TD promise that it had a
// better chain compared to ours. The only exception is if it's promised blocks were
// already imported by other means (e.g. fecher):
//
// R <remote peer>, L <local node>: Both at block 10
// R: Mine block 11, and propagate it to L
// L: Queue block 11 for import
// L: Notice that R's head and TD increased compared to ours, start sync
// L: Import of block 11 finishes
// L: Sync begins, and finds common ancestor at 11
// L: Request new hashes up from 11 (R's TD was higher, it must have something)
// R: Nothing to give
if !gotHashes && td.Cmp(d.headBlock().Td) > 0 {
return errStallingPeer
}
return nil
}
gotHashes = true
// Otherwise insert all the new hashes, aborting in case of junk
glog.V(logger.Detail).Infof("%v: inserting %d hashes from #%d", p, len(hashPack.hashes), from)
inserts := d.queue.Insert61(hashPack.hashes, true)
if len(inserts) != len(hashPack.hashes) {
glog.V(logger.Debug).Infof("%v: stale hashes", p)
return errBadPeer
}
// Notify the block fetcher of new hashes, but stop if queue is full
cont := d.queue.Pending() < maxQueuedHashes
select {
case d.processCh <- cont:
default:
}
if !cont {
return nil
}
// Queue not yet full, fetch the next batch
from += uint64(len(hashPack.hashes))
getHashes(from)
case <-timeout.C:
glog.V(logger.Debug).Infof("%v: hash request timed out", p)
hashTimeoutMeter.Mark(1)
return errTimeout
}
}
}
// fetchBlocks61 iteratively downloads the scheduled hashes, taking any available
// peers, reserving a chunk of blocks for each, waiting for delivery and also
// periodically checking for timeouts.
func (d *Downloader) fetchBlocks61(from uint64) error {
glog.V(logger.Debug).Infof("Downloading blocks from #%d", from)
defer glog.V(logger.Debug).Infof("Block download terminated")
// Create a timeout timer for scheduling expiration tasks
ticker := time.NewTicker(100 * time.Millisecond)
defer ticker.Stop()
update := make(chan struct{}, 1)
// Prepare the queue and fetch blocks until the hash fetcher's done
d.queue.Prepare(from)
finished := false
for {
select {
case <-d.cancelCh:
return errCancelBlockFetch
case <-d.headerCh:
// Out of bounds eth/62 block headers received, ignore them
case <-d.bodyCh:
// Out of bounds eth/62 block bodies received, ignore them
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 peer := d.peers.Peer(blockPack.peerId); peer != nil {
// Deliver the received chunk of blocks, and demote in case of errors
err := d.queue.Deliver61(blockPack.peerId, blockPack.blocks)
switch err {
case nil:
// If no blocks were delivered, demote the peer (need the delivery above)
if len(blockPack.blocks) == 0 {
peer.Demote()
peer.SetIdle61()
glog.V(logger.Detail).Infof("%s: no blocks delivered", peer)
break
}
// All was successful, promote the peer and potentially start processing
peer.Promote()
peer.SetIdle61()
glog.V(logger.Detail).Infof("%s: delivered %d blocks", peer, len(blockPack.blocks))
go d.process()
case errInvalidChain:
// The hash chain is invalid (blocks are not ordered properly), abort
return err
case errNoFetchesPending:
// Peer probably timed out with its delivery but came through
// in the end, demote, but allow to to pull from this peer.
peer.Demote()
peer.SetIdle61()
glog.V(logger.Detail).Infof("%s: out of bound delivery", peer)
case errStaleDelivery:
// Delivered something completely else than requested, usually
// caused by a timeout and delivery during a new sync cycle.
// Don't set it to idle as the original request should still be
// in flight.
peer.Demote()
glog.V(logger.Detail).Infof("%s: stale delivery", peer)
default:
// Peer did something semi-useful, demote but keep it around
peer.Demote()
peer.SetIdle61()
glog.V(logger.Detail).Infof("%s: delivery partially failed: %v", peer, err)
go d.process()
}
}
// Blocks arrived, try to update the progress
select {
case update <- struct{}{}:
default:
}
case cont := <-d.processCh:
// The hash fetcher sent a continuation flag, check if it's done
if !cont {
finished = true
}
// Hashes arrive, try to update the progress
select {
case update <- struct{}{}:
default:
}
case <-ticker.C:
// Sanity check update the progress
select {
case update <- struct{}{}:
default:
}
case <-update:
// Short circuit if we lost all our peers
if d.peers.Len() == 0 {
return errNoPeers
}
// Check for block request timeouts and demote the responsible peers
for _, pid := range d.queue.Expire(blockHardTTL) {
if peer := d.peers.Peer(pid); peer != nil {
peer.Demote()
glog.V(logger.Detail).Infof("%s: block delivery timeout", peer)
}
}
// If there's noting more to fetch, wait or terminate
if d.queue.Pending() == 0 {
if d.queue.InFlight() == 0 && finished {
glog.V(logger.Debug).Infof("Block fetching completed")
return nil
}
break
}
// Send a download request to all idle peers, until throttled
for _, peer := range d.peers.IdlePeers() {
// Short circuit if throttling activated
if d.queue.Throttle() {
break
}
// Reserve a chunk of hashes for a peer. A nil can mean either that
// no more hashes are available, or that the peer is known not to
// have them.
request := d.queue.Reserve61(peer, peer.Capacity())
if request == nil {
continue
}
if glog.V(logger.Detail) {
glog.Infof("%s: requesting %d blocks", peer, len(request.Hashes))
}
// Fetch the chunk and make sure any errors return the hashes to the queue
if err := peer.Fetch61(request); err != nil {
glog.V(logger.Error).Infof("%v: fetch failed, rescheduling", peer)
d.queue.Cancel(request)
}
}
// Make sure that we have peers available for fetching. If all peers have been tried
// and all failed throw an error
if !d.queue.Throttle() && d.queue.InFlight() == 0 {
return errPeersUnavailable
}
}
}
}
// findAncestor tries to locate the common ancestor block of the local chain and
// a remote peers blockchain. In the general case when our node was in sync and
// on the correct chain, checking the top N blocks should already get us a match.
// In the rare scenario when we ended up on a long reorganization (i.e. none of
// the head blocks match), we do a binary search to find the common ancestor.
func (d *Downloader) findAncestor(p *peer) (uint64, error) {
glog.V(logger.Debug).Infof("%v: looking for common ancestor", p)
// Request our head blocks to short circuit ancestor location
head := d.headBlock().NumberU64()
from := int64(head) - int64(MaxHeaderFetch) + 1
if from < 0 {
from = 0
}
go p.getAbsHeaders(uint64(from), MaxHeaderFetch, 0, false)
// Wait for the remote response to the head fetch
number, hash := uint64(0), common.Hash{}
timeout := time.After(hashTTL)
for finished := false; !finished; {
select {
case <-d.cancelCh:
return 0, errCancelHashFetch
case headerPack := <-d.headerCh:
// Discard anything not from the origin peer
if headerPack.peerId != p.id {
glog.V(logger.Debug).Infof("Received headers from incorrect peer(%s)", headerPack.peerId)
break
}
// Make sure the peer actually gave something valid
headers := headerPack.headers
if len(headers) == 0 {
glog.V(logger.Debug).Infof("%v: empty head header set", p)
return 0, errEmptyHeaderSet
}
// Check if a common ancestor was found
finished = true
for i := len(headers) - 1; i >= 0; i-- {
if d.hasBlock(headers[i].Hash()) {
number, hash = headers[i].Number.Uint64(), headers[i].Hash()
break
}
}
case <-d.bodyCh:
// Out of bounds block bodies received, ignore them
case <-d.hashCh:
// Out of bounds eth/61 hashes received, ignore them
case <-d.blockCh:
// Out of bounds eth/61 blocks received, ignore them
case <-timeout:
glog.V(logger.Debug).Infof("%v: head header timeout", p)
return 0, errTimeout
}
}
// If the head fetch already found an ancestor, return
if !common.EmptyHash(hash) {
glog.V(logger.Debug).Infof("%v: common ancestor: #%d [%x…]", p, number, hash[:4])
return number, nil
}
// Ancestor not found, we need to binary search over our chain
start, end := uint64(0), head
for start+1 < end {
// Split our chain interval in two, and request the hash to cross check
check := (start + end) / 2
timeout := time.After(hashTTL)
go p.getAbsHeaders(uint64(check), 1, 0, false)
// Wait until a reply arrives to this request
for arrived := false; !arrived; {
select {
case <-d.cancelCh:
return 0, errCancelHashFetch
case headerPack := <-d.headerCh:
// Discard anything not from the origin peer
if headerPack.peerId != p.id {
glog.V(logger.Debug).Infof("Received headers from incorrect peer(%s)", headerPack.peerId)
break
}
// Make sure the peer actually gave something valid
headers := headerPack.headers
if len(headers) != 1 {
glog.V(logger.Debug).Infof("%v: invalid search header set (%d)", p, len(headers))
return 0, errBadPeer
}
arrived = true
// Modify the search interval based on the response
block := d.getBlock(headers[0].Hash())
if block == nil {
end = check
break
}
if block.NumberU64() != check {
glog.V(logger.Debug).Infof("%v: non requested header #%d [%x…], instead of #%d", p, block.NumberU64(), block.Hash().Bytes()[:4], check)
return 0, errBadPeer
}
start = check
case <-d.bodyCh:
// Out of bounds block bodies received, ignore them
case <-d.hashCh:
// Out of bounds eth/61 hashes received, ignore them
case <-d.blockCh:
// Out of bounds eth/61 blocks received, ignore them
case <-timeout:
glog.V(logger.Debug).Infof("%v: search header timeout", p)
return 0, errTimeout
}
}
}
return start, nil
}
// fetchHeaders keeps retrieving headers from the requested number, until no more
// are returned, potentially throttling on the way.
func (d *Downloader) fetchHeaders(p *peer, td *big.Int, from uint64) error {
glog.V(logger.Debug).Infof("%v: downloading headers from #%d", p, from)
defer glog.V(logger.Debug).Infof("%v: header download terminated", p)
// Create a timeout timer, and the associated hash fetcher
request := time.Now() // time of the last fetch request
timeout := time.NewTimer(0) // timer to dump a non-responsive active peer
<-timeout.C // timeout channel should be initially empty
defer timeout.Stop()
getHeaders := func(from uint64) {
glog.V(logger.Detail).Infof("%v: fetching %d headers from #%d", p, MaxHeaderFetch, from)
go p.getAbsHeaders(from, MaxHeaderFetch, 0, false)
request = time.Now()
timeout.Reset(headerTTL)
}
// Start pulling headers, until all are exhausted
getHeaders(from)
gotHeaders := false
for {
select {
case <-d.cancelCh:
return errCancelHeaderFetch
case <-d.hashCh:
// Out of bounds eth/61 hashes received, ignore them
case <-d.blockCh:
// Out of bounds eth/61 blocks received, ignore them
case headerPack := <-d.headerCh:
// Make sure the active peer is giving us the headers
if headerPack.peerId != p.id {
glog.V(logger.Debug).Infof("Received headers from incorrect peer (%s)", headerPack.peerId)
break
}
headerReqTimer.UpdateSince(request)
timeout.Stop()
// If no more headers are inbound, notify the body fetcher and return
if len(headerPack.headers) == 0 {
glog.V(logger.Debug).Infof("%v: no available headers", p)
select {
case d.processCh <- false:
case <-d.cancelCh:
}
// If no headers were retrieved at all, the peer violated it's TD promise that it had a
// better chain compared to ours. The only exception is if it's promised blocks were
// already imported by other means (e.g. fecher):
//
// R <remote peer>, L <local node>: Both at block 10
// R: Mine block 11, and propagate it to L
// L: Queue block 11 for import
// L: Notice that R's head and TD increased compared to ours, start sync
// L: Import of block 11 finishes
// L: Sync begins, and finds common ancestor at 11
// L: Request new headers up from 11 (R's TD was higher, it must have something)
// R: Nothing to give
if !gotHeaders && td.Cmp(d.headBlock().Td) > 0 {
return errStallingPeer
}
return nil
}
gotHeaders = true
// Otherwise insert all the new headers, aborting in case of junk
glog.V(logger.Detail).Infof("%v: inserting %d headers from #%d", p, len(headerPack.headers), from)
inserts := d.queue.Insert(headerPack.headers)
if len(inserts) != len(headerPack.headers) {
glog.V(logger.Debug).Infof("%v: stale headers", p)
return errBadPeer
}
// Notify the block fetcher of new headers, but stop if queue is full
cont := d.queue.Pending() < maxQueuedHeaders
select {
case d.processCh <- cont:
default:
}
if !cont {
return nil
}
// Queue not yet full, fetch the next batch
from += uint64(len(headerPack.headers))
getHeaders(from)
case <-timeout.C:
// Header retrieval timed out, consider the peer bad and drop
glog.V(logger.Debug).Infof("%v: header request timed out", p)
headerTimeoutMeter.Mark(1)
d.dropPeer(p.id)
// Finish the sync gracefully instead of dumping the gathered data though
select {
case d.processCh <- false:
default:
}
return nil
}
}
}
// fetchBodies iteratively downloads the scheduled block bodies, taking any
// available peers, reserving a chunk of blocks for each, waiting for delivery
// and also periodically checking for timeouts.
func (d *Downloader) fetchBodies(from uint64) error {
glog.V(logger.Debug).Infof("Downloading block bodies from #%d", from)
defer glog.V(logger.Debug).Infof("Block body download terminated")
// Create a timeout timer for scheduling expiration tasks
ticker := time.NewTicker(100 * time.Millisecond)
defer ticker.Stop()
update := make(chan struct{}, 1)
// Prepare the queue and fetch block bodies until the block header fetcher's done
d.queue.Prepare(from)
finished := false
for {
select {
case <-d.cancelCh:
return errCancelBlockFetch
case <-d.hashCh:
// Out of bounds eth/61 hashes received, ignore them
case <-d.blockCh:
// Out of bounds eth/61 blocks received, ignore them
case bodyPack := <-d.bodyCh:
// If the peer was previously banned and failed to deliver it's pack
// in a reasonable time frame, ignore it's message.
if peer := d.peers.Peer(bodyPack.peerId); peer != nil {
// Deliver the received chunk of bodies, and demote in case of errors
err := d.queue.Deliver(bodyPack.peerId, bodyPack.transactions, bodyPack.uncles)
switch err {
case nil:
// If no blocks were delivered, demote the peer (need the delivery above)
if len(bodyPack.transactions) == 0 || len(bodyPack.uncles) == 0 {
peer.Demote()
peer.SetIdle()
glog.V(logger.Detail).Infof("%s: no block bodies delivered", peer)
break
}
// All was successful, promote the peer and potentially start processing
peer.Promote()
peer.SetIdle()
glog.V(logger.Detail).Infof("%s: delivered %d:%d block bodies", peer, len(bodyPack.transactions), len(bodyPack.uncles))
go d.process()
case errInvalidChain:
// The hash chain is invalid (blocks are not ordered properly), abort
return err
case errInvalidBody:
// The peer delivered something very bad, drop immediately
glog.V(logger.Error).Infof("%s: delivered invalid block, dropping", peer)
d.dropPeer(peer.id)
case errNoFetchesPending:
// Peer probably timed out with its delivery but came through
// in the end, demote, but allow to to pull from this peer.
peer.Demote()
peer.SetIdle()
glog.V(logger.Detail).Infof("%s: out of bound delivery", peer)
case errStaleDelivery:
// Delivered something completely else than requested, usually
// caused by a timeout and delivery during a new sync cycle.
// Don't set it to idle as the original request should still be
// in flight.
peer.Demote()
glog.V(logger.Detail).Infof("%s: stale delivery", peer)
default:
// Peer did something semi-useful, demote but keep it around
peer.Demote()
peer.SetIdle()
glog.V(logger.Detail).Infof("%s: delivery partially failed: %v", peer, err)
go d.process()
}
}
// Blocks assembled, try to update the progress
select {
case update <- struct{}{}:
default:
}
case cont := <-d.processCh:
// The header fetcher sent a continuation flag, check if it's done
if !cont {
finished = true
}
// Headers arrive, try to update the progress
select {
case update <- struct{}{}:
default:
}
case <-ticker.C:
// Sanity check update the progress
select {
case update <- struct{}{}:
default:
}
case <-update:
// Short circuit if we lost all our peers
if d.peers.Len() == 0 {
return errNoPeers
}
// Check for block body request timeouts and demote the responsible peers
for _, pid := range d.queue.Expire(bodyHardTTL) {
if peer := d.peers.Peer(pid); peer != nil {
peer.Demote()
glog.V(logger.Detail).Infof("%s: block body delivery timeout", peer)
}
}
// If there's noting more to fetch, wait or terminate
if d.queue.Pending() == 0 {
if d.queue.InFlight() == 0 && finished {
glog.V(logger.Debug).Infof("Block body fetching completed")
return nil
}
break
}
// Send a download request to all idle peers, until throttled
queuedEmptyBlocks, throttled := false, false
for _, peer := range d.peers.IdlePeers() {
// Short circuit if throttling activated
if d.queue.Throttle() {
throttled = true
break
}
// Reserve a chunk of hashes for a peer. A nil can mean either that
// no more hashes are available, or that the peer is known not to
// have them.
request, process, err := d.queue.Reserve(peer, peer.Capacity())
if err != nil {
return err
}
if process {
queuedEmptyBlocks = true
go d.process()
}
if request == nil {
continue
}
if glog.V(logger.Detail) {
glog.Infof("%s: requesting %d block bodies", peer, len(request.Headers))
}
// Fetch the chunk and make sure any errors return the hashes to the queue
if d.bodyFetchHook != nil {
d.bodyFetchHook(request.Headers)
}
if err := peer.Fetch(request); err != nil {
glog.V(logger.Error).Infof("%v: fetch failed, rescheduling", peer)
d.queue.Cancel(request)
}
}
// Make sure that we have peers available for fetching. If all peers have been tried
// and all failed throw an error
if !queuedEmptyBlocks && !throttled && d.queue.InFlight() == 0 {
return errPeersUnavailable
}
}
}
}
// process takes blocks from the queue and tries to import them into the chain.
//
// The algorithmic flow is as follows:
// - The `processing` flag is swapped to 1 to ensure singleton access
// - The current `cancel` channel is retrieved to detect sync abortions
// - Blocks are iteratively taken from the cache and inserted into the chain
// - When the cache becomes empty, insertion stops
// - The `processing` flag is swapped back to 0
// - A post-exit check is made whether new blocks became available
// - This step is important: it handles a potential race condition between
// checking for no more work, and releasing the processing "mutex". In
// between these state changes, a block may have arrived, but a processing
// attempt denied, so we need to re-enter to ensure the block isn't left
// to idle in the cache.
func (d *Downloader) process() {
// Make sure only one goroutine is ever allowed to process blocks at once
if !atomic.CompareAndSwapInt32(&d.processing, 0, 1) {
return
}
// If the processor just exited, but there are freshly pending items, try to
// reenter. This is needed because the goroutine spinned up for processing
// the fresh blocks might have been rejected entry to to this present thread
// not yet releasing the `processing` state.
defer func() {
if atomic.LoadInt32(&d.interrupt) == 0 && d.queue.GetHeadBlock() != nil {
d.process()
}
}()
// Release the lock upon exit (note, before checking for reentry!), and set
// the import statistics to zero.
defer func() {
d.importLock.Lock()
d.importQueue = nil
d.importDone = 0
d.importLock.Unlock()
atomic.StoreInt32(&d.processing, 0)
}()
// Repeat the processing as long as there are blocks to import
for {
// Fetch the next batch of blocks
blocks := d.queue.TakeBlocks()
if len(blocks) == 0 {
return
}
if d.chainInsertHook != nil {
d.chainInsertHook(blocks)
}
// Reset the import statistics
d.importLock.Lock()
d.importStart = time.Now()
d.importQueue = blocks
d.importDone = 0
d.importLock.Unlock()
// Actually import the blocks
glog.V(logger.Debug).Infof("Inserting chain with %d blocks (#%v - #%v)\n", len(blocks), blocks[0].RawBlock.Number(), blocks[len(blocks)-1].RawBlock.Number())
for len(blocks) != 0 {
// Check for any termination requests
if atomic.LoadInt32(&d.interrupt) == 1 {
return
}
// Retrieve the first batch of blocks to insert
max := int(math.Min(float64(len(blocks)), float64(maxBlockProcess)))
raw := make(types.Blocks, 0, max)
for _, block := range blocks[:max] {
raw = append(raw, block.RawBlock)
}
// Try to inset the blocks, drop the originating peer if there's an error
index, err := d.insertChain(raw)
if err != nil {
glog.V(logger.Debug).Infof("Block #%d import failed: %v", raw[index].NumberU64(), err)
d.dropPeer(blocks[index].OriginPeer)
d.cancel()
return
}
blocks = blocks[max:]
}
}
}
// DeliverHashes61 injects a new batch of hashes received from a remote node into
// the download schedule. This is usually invoked through the BlockHashesMsg by
// the protocol handler.
func (d *Downloader) DeliverHashes61(id string, hashes []common.Hash) (err error) {
// Update the delivery metrics for both good and failed deliveries
hashInMeter.Mark(int64(len(hashes)))
defer func() {
if err != nil {
hashDropMeter.Mark(int64(len(hashes)))
}
}()
// Make sure the downloader is active
if atomic.LoadInt32(&d.synchronising) == 0 {
return errNoSyncActive
}
// Deliver or abort if the sync is canceled while queuing
d.cancelLock.RLock()
cancel := d.cancelCh
d.cancelLock.RUnlock()
select {
case d.hashCh <- hashPack{id, hashes}:
return nil
case <-cancel:
return errNoSyncActive
}
}
// DeliverBlocks61 injects a new batch of blocks received from a remote node.
// This is usually invoked through the BlocksMsg by the protocol handler.
func (d *Downloader) DeliverBlocks61(id string, blocks []*types.Block) (err error) {
// Update the delivery metrics for both good and failed deliveries
blockInMeter.Mark(int64(len(blocks)))
defer func() {
if err != nil {
blockDropMeter.Mark(int64(len(blocks)))
}
}()
// Make sure the downloader is active
if atomic.LoadInt32(&d.synchronising) == 0 {
return errNoSyncActive
}
// Deliver or abort if the sync is canceled while queuing
d.cancelLock.RLock()
cancel := d.cancelCh
d.cancelLock.RUnlock()
select {
case d.blockCh <- blockPack{id, blocks}:
return nil
case <-cancel:
return errNoSyncActive
}
2015-04-19 15:14:15 +00:00
}
// DeliverHeaders injects a new batch of blck headers received from a remote
// node into the download schedule.
func (d *Downloader) DeliverHeaders(id string, headers []*types.Header) (err error) {
// Update the delivery metrics for both good and failed deliveries
headerInMeter.Mark(int64(len(headers)))
defer func() {
if err != nil {
headerDropMeter.Mark(int64(len(headers)))
}
}()
// Make sure the downloader is active
if atomic.LoadInt32(&d.synchronising) == 0 {
return errNoSyncActive
}
// Deliver or abort if the sync is canceled while queuing
d.cancelLock.RLock()
cancel := d.cancelCh
d.cancelLock.RUnlock()
2015-04-12 10:38:25 +00:00
select {
case d.headerCh <- headerPack{id, headers}:
return nil
case <-cancel:
return errNoSyncActive
}
}
// DeliverBodies injects a new batch of block bodies received from a remote node.
func (d *Downloader) DeliverBodies(id string, transactions [][]*types.Transaction, uncles [][]*types.Header) (err error) {
// Update the delivery metrics for both good and failed deliveries
bodyInMeter.Mark(int64(len(transactions)))
defer func() {
if err != nil {
bodyDropMeter.Mark(int64(len(transactions)))
}
}()
// Make sure the downloader is active
if atomic.LoadInt32(&d.synchronising) == 0 {
return errNoSyncActive
}
// Deliver or abort if the sync is canceled while queuing
d.cancelLock.RLock()
cancel := d.cancelCh
d.cancelLock.RUnlock()
select {
case d.bodyCh <- bodyPack{id, transactions, uncles}:
return nil
case <-cancel:
return errNoSyncActive
}
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}