Official Go implementation of the Ethereum protocol
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go-ethereum/eth/downloader/peer.go

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9.6 KiB

// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// 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,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// 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/>.
// Contains the active peer-set of the downloader, maintaining both failures
// as well as reputation metrics to prioritize the block retrievals.
package downloader
import (
"errors"
"math/big"
"sync"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/eth/protocols/eth"
"github.com/ethereum/go-ethereum/event"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/p2p/msgrate"
)
const (
maxLackingHashes = 4096 // Maximum number of entries allowed on the list or lacking items
)
var (
errAlreadyRegistered = errors.New("peer is already registered")
errNotRegistered = errors.New("peer is not registered")
)
// peerConnection represents an active peer from which hashes and blocks are retrieved.
type peerConnection struct {
id string // Unique identifier of the peer
rates *msgrate.Tracker // Tracker to hone in on the number of items retrievable per second
lacking map[common.Hash]struct{} // Set of hashes not to request (didn't have previously)
peer Peer
version uint // Eth protocol version number to switch strategies
log log.Logger // Contextual logger to add extra infos to peer logs
lock sync.RWMutex
}
// LightPeer encapsulates the methods required to synchronise with a remote light peer.
type LightPeer interface {
Head() (common.Hash, *big.Int)
RequestHeadersByHash(common.Hash, int, int, bool, chan *eth.Response) (*eth.Request, error)
RequestHeadersByNumber(uint64, int, int, bool, chan *eth.Response) (*eth.Request, error)
}
// Peer encapsulates the methods required to synchronise with a remote full peer.
type Peer interface {
LightPeer
RequestBodies([]common.Hash, chan *eth.Response) (*eth.Request, error)
RequestReceipts([]common.Hash, chan *eth.Response) (*eth.Request, error)
}
// lightPeerWrapper wraps a LightPeer struct, stubbing out the Peer-only methods.
type lightPeerWrapper struct {
peer LightPeer
}
func (w *lightPeerWrapper) Head() (common.Hash, *big.Int) { return w.peer.Head() }
func (w *lightPeerWrapper) RequestHeadersByHash(h common.Hash, amount int, skip int, reverse bool, sink chan *eth.Response) (*eth.Request, error) {
return w.peer.RequestHeadersByHash(h, amount, skip, reverse, sink)
}
func (w *lightPeerWrapper) RequestHeadersByNumber(i uint64, amount int, skip int, reverse bool, sink chan *eth.Response) (*eth.Request, error) {
return w.peer.RequestHeadersByNumber(i, amount, skip, reverse, sink)
}
func (w *lightPeerWrapper) RequestBodies([]common.Hash, chan *eth.Response) (*eth.Request, error) {
panic("RequestBodies not supported in light client mode sync")
}
func (w *lightPeerWrapper) RequestReceipts([]common.Hash, chan *eth.Response) (*eth.Request, error) {
panic("RequestReceipts not supported in light client mode sync")
}
// newPeerConnection creates a new downloader peer.
func newPeerConnection(id string, version uint, peer Peer, logger log.Logger) *peerConnection {
return &peerConnection{
id: id,
lacking: make(map[common.Hash]struct{}),
peer: peer,
version: version,
log: logger,
}
}
// Reset clears the internal state of a peer entity.
func (p *peerConnection) Reset() {
p.lock.Lock()
defer p.lock.Unlock()
p.lacking = make(map[common.Hash]struct{})
}
// UpdateHeaderRate updates the peer's estimated header retrieval throughput with
// the current measurement.
func (p *peerConnection) UpdateHeaderRate(delivered int, elapsed time.Duration) {
p.rates.Update(eth.BlockHeadersMsg, elapsed, delivered)
}
// UpdateBodyRate updates the peer's estimated body retrieval throughput with the
// current measurement.
func (p *peerConnection) UpdateBodyRate(delivered int, elapsed time.Duration) {
p.rates.Update(eth.BlockBodiesMsg, elapsed, delivered)
}
// UpdateReceiptRate updates the peer's estimated receipt retrieval throughput
// with the current measurement.
func (p *peerConnection) UpdateReceiptRate(delivered int, elapsed time.Duration) {
p.rates.Update(eth.ReceiptsMsg, elapsed, delivered)
}
// HeaderCapacity retrieves the peer's header download allowance based on its
// previously discovered throughput.
func (p *peerConnection) HeaderCapacity(targetRTT time.Duration) int {
cap := p.rates.Capacity(eth.BlockHeadersMsg, targetRTT)
if cap > MaxHeaderFetch {
cap = MaxHeaderFetch
}
return cap
}
// BodyCapacity retrieves the peer's body download allowance based on its
// previously discovered throughput.
func (p *peerConnection) BodyCapacity(targetRTT time.Duration) int {
cap := p.rates.Capacity(eth.BlockBodiesMsg, targetRTT)
if cap > MaxBlockFetch {
cap = MaxBlockFetch
}
return cap
}
// ReceiptCapacity retrieves the peers receipt download allowance based on its
// previously discovered throughput.
func (p *peerConnection) ReceiptCapacity(targetRTT time.Duration) int {
cap := p.rates.Capacity(eth.ReceiptsMsg, targetRTT)
if cap > MaxReceiptFetch {
cap = MaxReceiptFetch
}
return cap
}
// MarkLacking appends a new entity to the set of items (blocks, receipts, states)
// that a peer is known not to have (i.e. have been requested before). If the
// set reaches its maximum allowed capacity, items are randomly dropped off.
func (p *peerConnection) MarkLacking(hash common.Hash) {
p.lock.Lock()
defer p.lock.Unlock()
for len(p.lacking) >= maxLackingHashes {
for drop := range p.lacking {
delete(p.lacking, drop)
break
}
}
p.lacking[hash] = struct{}{}
}
// Lacks retrieves whether the hash of a blockchain item is on the peers lacking
// list (i.e. whether we know that the peer does not have it).
func (p *peerConnection) Lacks(hash common.Hash) bool {
p.lock.RLock()
defer p.lock.RUnlock()
_, ok := p.lacking[hash]
return ok
}
// peeringEvent is sent on the peer event feed when a remote peer connects or
// disconnects.
type peeringEvent struct {
peer *peerConnection
join bool
}
// peerSet represents the collection of active peer participating in the chain
// download procedure.
type peerSet struct {
peers map[string]*peerConnection
rates *msgrate.Trackers // Set of rate trackers to give the sync a common beat
events event.Feed // Feed to publish peer lifecycle events on
lock sync.RWMutex
}
// newPeerSet creates a new peer set top track the active download sources.
func newPeerSet() *peerSet {
return &peerSet{
peers: make(map[string]*peerConnection),
rates: msgrate.NewTrackers(log.New("proto", "eth")),
}
}
// SubscribeEvents subscribes to peer arrival and departure events.
func (ps *peerSet) SubscribeEvents(ch chan<- *peeringEvent) event.Subscription {
return ps.events.Subscribe(ch)
}
// Reset iterates over the current peer set, and resets each of the known peers
// to prepare for a next batch of block retrieval.
func (ps *peerSet) Reset() {
ps.lock.RLock()
defer ps.lock.RUnlock()
for _, peer := range ps.peers {
peer.Reset()
}
}
// Register injects a new peer into the working set, or returns an error if the
// peer is already known.
//
// The method also sets the starting throughput values of the new peer to the
// average of all existing peers, to give it a realistic chance of being used
// for data retrievals.
func (ps *peerSet) Register(p *peerConnection) error {
// Register the new peer with some meaningful defaults
ps.lock.Lock()
if _, ok := ps.peers[p.id]; ok {
ps.lock.Unlock()
return errAlreadyRegistered
}
p.rates = msgrate.NewTracker(ps.rates.MeanCapacities(), ps.rates.MedianRoundTrip())
if err := ps.rates.Track(p.id, p.rates); err != nil {
return err
}
ps.peers[p.id] = p
ps.lock.Unlock()
ps.events.Send(&peeringEvent{peer: p, join: true})
return nil
}
// Unregister removes a remote peer from the active set, disabling any further
// actions to/from that particular entity.
func (ps *peerSet) Unregister(id string) error {
ps.lock.Lock()
p, ok := ps.peers[id]
if !ok {
ps.lock.Unlock()
return errNotRegistered
}
delete(ps.peers, id)
ps.rates.Untrack(id)
ps.lock.Unlock()
ps.events.Send(&peeringEvent{peer: p, join: false})
return nil
}
// Peer retrieves the registered peer with the given id.
func (ps *peerSet) Peer(id string) *peerConnection {
ps.lock.RLock()
defer ps.lock.RUnlock()
return ps.peers[id]
}
// Len returns if the current number of peers in the set.
func (ps *peerSet) Len() int {
ps.lock.RLock()
defer ps.lock.RUnlock()
return len(ps.peers)
}
// AllPeers retrieves a flat list of all the peers within the set.
func (ps *peerSet) AllPeers() []*peerConnection {
ps.lock.RLock()
defer ps.lock.RUnlock()
list := make([]*peerConnection, 0, len(ps.peers))
for _, p := range ps.peers {
list = append(list, p)
}
return list
}
// peerCapacitySort implements sort.Interface.
// It sorts peer connections by capacity (descending).
type peerCapacitySort struct {
p []*peerConnection
tp []int
}
func (ps *peerCapacitySort) Len() int {
return len(ps.p)
}
func (ps *peerCapacitySort) Less(i, j int) bool {
return ps.tp[i] > ps.tp[j]
}
func (ps *peerCapacitySort) Swap(i, j int) {
ps.p[i], ps.p[j] = ps.p[j], ps.p[i]
ps.tp[i], ps.tp[j] = ps.tp[j], ps.tp[i]
}