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peer_tracker.go
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peer_tracker.go
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// (c) 2019-2022, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.
package peer
import (
"math"
"math/rand"
"time"
"github.com/ava-labs/avalanchego/ids"
utils_math "github.com/ava-labs/avalanchego/utils/math"
"github.com/ava-labs/avalanchego/utils/set"
"github.com/ava-labs/avalanchego/version"
"github.com/ethereum/go-ethereum/log"
"github.com/bilgin-kocak/subnet-evm/metrics"
)
const (
bandwidthHalflife = 5 * time.Minute
// controls how eagerly we connect to new peers vs. using
// peers with known good response bandwidth.
desiredMinResponsivePeers = 20
newPeerConnectFactor = 0.1
// controls how often we prefer a random responsive peer over the most
// performant peer.
randomPeerProbability = 0.2
)
// information we track on a given peer
type peerInfo struct {
version *version.Application
bandwidth utils_math.Averager
}
// peerTracker tracks the bandwidth of responses coming from peers,
// preferring to contact peers with known good bandwidth, connecting
// to new peers with an exponentially decaying probability.
// Note: is not thread safe, caller must handle synchronization.
type peerTracker struct {
peers map[ids.NodeID]*peerInfo // all peers we are connected to
numTrackedPeers metrics.Gauge
trackedPeers set.Set[ids.NodeID] // peers that we have sent a request to
numResponsivePeers metrics.Gauge
responsivePeers set.Set[ids.NodeID] // peers that responded to the last request they were sent
bandwidthHeap utils_math.AveragerHeap // tracks bandwidth peers are responding with
averageBandwidthMetric metrics.GaugeFloat64
averageBandwidth utils_math.Averager
}
func NewPeerTracker() *peerTracker {
return &peerTracker{
peers: make(map[ids.NodeID]*peerInfo),
numTrackedPeers: metrics.GetOrRegisterGauge("net_tracked_peers", nil),
trackedPeers: make(set.Set[ids.NodeID]),
numResponsivePeers: metrics.GetOrRegisterGauge("net_responsive_peers", nil),
responsivePeers: make(set.Set[ids.NodeID]),
bandwidthHeap: utils_math.NewMaxAveragerHeap(),
averageBandwidthMetric: metrics.GetOrRegisterGaugeFloat64("net_average_bandwidth", nil),
averageBandwidth: utils_math.NewAverager(0, bandwidthHalflife, time.Now()),
}
}
// shouldTrackNewPeer returns true if we are not connected to enough peers.
// otherwise returns true probabilistically based on the number of tracked peers.
func (p *peerTracker) shouldTrackNewPeer() bool {
numResponsivePeers := p.responsivePeers.Len()
if numResponsivePeers < desiredMinResponsivePeers {
return true
}
if len(p.trackedPeers) >= len(p.peers) {
// already tracking all the peers
return false
}
newPeerProbability := math.Exp(-float64(numResponsivePeers) * newPeerConnectFactor)
return rand.Float64() < newPeerProbability
}
// getResponsivePeer returns a random [ids.NodeID] of a peer that has responded
// to a request.
func (p *peerTracker) getResponsivePeer() (ids.NodeID, utils_math.Averager, bool) {
nodeID, ok := p.responsivePeers.Peek()
if !ok {
return ids.NodeID{}, nil, false
}
averager, ok := p.bandwidthHeap.Remove(nodeID)
if ok {
return nodeID, averager, true
}
peer := p.peers[nodeID]
return nodeID, peer.bandwidth, true
}
func (p *peerTracker) GetAnyPeer(minVersion *version.Application) (ids.NodeID, bool) {
if p.shouldTrackNewPeer() {
for nodeID := range p.peers {
// if minVersion is specified and peer's version is less, skip
if minVersion != nil && p.peers[nodeID].version.Compare(minVersion) < 0 {
continue
}
// skip peers already tracked
if p.trackedPeers.Contains(nodeID) {
continue
}
log.Debug("peer tracking: connecting to new peer", "trackedPeers", len(p.trackedPeers), "nodeID", nodeID)
return nodeID, true
}
}
var (
nodeID ids.NodeID
ok bool
random bool
averager utils_math.Averager
)
if rand.Float64() < randomPeerProbability {
random = true
nodeID, averager, ok = p.getResponsivePeer()
} else {
nodeID, averager, ok = p.bandwidthHeap.Pop()
}
if ok {
log.Debug("peer tracking: popping peer", "nodeID", nodeID, "bandwidth", averager.Read(), "random", random)
return nodeID, true
}
// if no nodes found in the bandwidth heap, return a tracked node at random
return p.trackedPeers.Peek()
}
func (p *peerTracker) TrackPeer(nodeID ids.NodeID) {
p.trackedPeers.Add(nodeID)
p.numTrackedPeers.Update(int64(p.trackedPeers.Len()))
}
func (p *peerTracker) TrackBandwidth(nodeID ids.NodeID, bandwidth float64) {
peer := p.peers[nodeID]
if peer == nil {
// we're not connected to this peer, nothing to do here
log.Debug("tracking bandwidth for untracked peer", "nodeID", nodeID)
return
}
now := time.Now()
if peer.bandwidth == nil {
peer.bandwidth = utils_math.NewAverager(bandwidth, bandwidthHalflife, now)
} else {
peer.bandwidth.Observe(bandwidth, now)
}
p.bandwidthHeap.Add(nodeID, peer.bandwidth)
if bandwidth == 0 {
p.responsivePeers.Remove(nodeID)
} else {
p.responsivePeers.Add(nodeID)
p.averageBandwidth.Observe(bandwidth, now)
p.averageBandwidthMetric.Update(p.averageBandwidth.Read())
}
p.numResponsivePeers.Update(int64(p.responsivePeers.Len()))
}
// Connected should be called when [nodeID] connects to this node
func (p *peerTracker) Connected(nodeID ids.NodeID, nodeVersion *version.Application) {
if peer := p.peers[nodeID]; peer != nil {
// Peer is already connected, update the version if it has changed.
// Log a warning message since the consensus engine should never call Connected on a peer
// that we have already marked as Connected.
if nodeVersion.Compare(peer.version) != 0 {
p.peers[nodeID] = &peerInfo{
version: nodeVersion,
bandwidth: peer.bandwidth,
}
log.Warn("updating node version of already connected peer", "nodeID", nodeID, "storedVersion", peer.version, "nodeVersion", nodeVersion)
} else {
log.Warn("ignoring peer connected event for already connected peer with identical version", "nodeID", nodeID)
}
return
}
p.peers[nodeID] = &peerInfo{
version: nodeVersion,
}
}
// Disconnected should be called when [nodeID] disconnects from this node
func (p *peerTracker) Disconnected(nodeID ids.NodeID) {
p.bandwidthHeap.Remove(nodeID)
p.trackedPeers.Remove(nodeID)
p.numTrackedPeers.Update(int64(p.trackedPeers.Len()))
p.responsivePeers.Remove(nodeID)
p.numResponsivePeers.Update(int64(p.responsivePeers.Len()))
delete(p.peers, nodeID)
}
// Size returns the number of peers the node is connected to
func (p *peerTracker) Size() int {
return len(p.peers)
}