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peermgr.go
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/
peermgr.go
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package exchange
import (
"context"
"errors"
"fmt"
"io"
"sync"
"time"
cborutil "github.com/filecoin-project/go-cbor-util"
"github.com/ipfs/go-cid"
"github.com/libp2p/go-eventbus"
"github.com/libp2p/go-libp2p-core/event"
"github.com/libp2p/go-libp2p-core/host"
"github.com/libp2p/go-libp2p-core/network"
"github.com/libp2p/go-libp2p-core/peer"
"github.com/rs/zerolog/log"
)
// HeyProtocol identifies the supply greeter protocol
const HeyProtocol = "/myel/pop/hey/1.0"
//go:generate cbor-gen-for Hey
// Hey is the greeting message which takes in network info
type Hey struct {
Regions []RegionCode
IndexRoot *cid.Cid // If the node has an empty index the root will be nil
}
// HeyEvt is emitted when a Hey is received and accessible via the libp2p event bus subscription
type HeyEvt struct {
Peer peer.ID
IndexRoot *cid.Cid // nil index root means empty index i.e. brand new node
}
// Peer contains information recorded while interacted with a peer
type Peer struct {
Regions []RegionCode
Latency time.Duration
}
// PeerMgr is in charge of maintaining an optimal network of peers to coordinate with
type PeerMgr struct {
h host.Host
regions map[RegionCode]Region
emitter event.Emitter
idx *Index
mu sync.Mutex
peers map[peer.ID]Peer
}
// NewPeerMgr prepares a new PeerMgr instance
func NewPeerMgr(h host.Host, idx *Index, regions []Region) *PeerMgr {
reg := make(map[RegionCode]Region, len(regions))
for _, r := range regions {
reg[r.Code] = r
}
emitter, err := h.EventBus().Emitter(new(HeyEvt))
if err != nil {
log.Error().Err(err).Msg("failed to create emitter event")
}
pm := &PeerMgr{
h: h,
regions: reg,
idx: idx,
peers: make(map[peer.ID]Peer),
emitter: emitter,
}
h.Network().Notify(&network.NotifyBundle{
DisconnectedF: func(_ network.Network, c network.Conn) {
pm.mu.Lock()
defer pm.mu.Unlock()
if _, ok := pm.peers[c.RemotePeer()]; ok {
delete(pm.peers, c.RemotePeer())
}
},
})
return pm
}
func (pm *PeerMgr) Run(ctx context.Context) error {
pm.h.SetStreamHandler(HeyProtocol, pm.handleStream)
sub, err := pm.h.EventBus().Subscribe(new(event.EvtPeerIdentificationCompleted), eventbus.BufSize(1024))
if err != nil {
return fmt.Errorf("failed to subscribe to event bus: %w", err)
}
go func() {
for evt := range sub.Out() {
pic := evt.(event.EvtPeerIdentificationCompleted)
go func() {
if err := pm.sendHey(ctx, pic.Peer); err != nil {
return
}
}()
}
}()
return nil
}
// Peers returns n active peers for a given list of regions and peers to ignore
func (pm *PeerMgr) Peers(n int, rl []Region, ignore map[peer.ID]bool, init []peer.ID) []peer.ID {
var peers []peer.ID
if n == 0 {
return peers
}
pm.mu.Lock()
defer pm.mu.Unlock()
// add initial peers first
for _, p := range init {
// peers not connected will be ignored
if _, ok := pm.peers[p]; ok && !ignore[p] {
peers = append(peers, p)
}
}
// Check if we have enough peers and return
if len(peers) == n {
return peers
}
for _, r := range rl {
for p, v := range pm.peers {
if ignore[p] {
continue
}
for _, rc := range v.Regions {
if rc == r.Code {
peers = append(peers, p)
}
}
// Check if we have enough peers and return
if len(peers) == n {
return peers
}
}
}
return peers
}
// handleStream is the multistream handler for the Hey protocol, it reads a Hey message and handles it
func (pm *PeerMgr) handleStream(s network.Stream) {
var hmsg Hey
if err := cborutil.ReadCborRPC(s, &hmsg); err != nil {
connErr := s.Conn().Close()
if connErr != nil {
log.Error().Err(connErr).Msg("could not close stream connection")
}
log.Error().Err(err).Msg("failed to read CBOR Hey msg")
return
}
pm.handleHey(s.Conn().RemotePeer(), hmsg)
// We send back the seed to measure roundrip time
go func() {
defer s.Close()
buf := make([]byte, 32)
_, err := s.Write(buf)
if err != nil {
log.Error().Err(err).Msg("could not write bytes")
}
}()
}
// Receive a new greeting from peer
func (pm *PeerMgr) handleHey(p peer.ID, h Hey) {
for _, r := range h.Regions {
// We only save peers who are in the same region as us
if reg, ok := pm.regions[r]; ok {
err := pm.emitter.Emit(HeyEvt{
Peer: p,
IndexRoot: h.IndexRoot,
})
if err != nil {
log.Error().Err(err).Msg("failed to emit event")
}
// These peers should be trimmed last when the number of connections overflows
pm.h.ConnManager().TagPeer(p, reg.Name, 10)
pm.mu.Lock()
pm.peers[p] = Peer{
Regions: h.Regions,
}
pm.mu.Unlock()
}
}
}
// sendHey message to a given peer
func (pm *PeerMgr) sendHey(ctx context.Context, pid peer.ID) error {
s, err := pm.h.NewStream(ctx, pid, HeyProtocol)
if err != nil {
return err
}
hmsg := pm.getHey()
start := time.Now()
if err := cborutil.WriteCborRPC(s, &hmsg); err != nil {
return err
}
go func() {
defer s.Close()
s.SetReadDeadline(time.Now().Add(10 * time.Second))
buf := make([]byte, 32)
_, err := io.ReadFull(s, buf)
if err != nil {
log.Error().Err(err).Msg("failed to read pong msg")
}
pm.recordLatency(pid, time.Now(), start)
}()
return nil
}
// getHey formats a new Hey message
func (pm *PeerMgr) getHey() Hey {
regions := make([]RegionCode, len(pm.regions))
i := 0
for _, rg := range pm.regions {
regions[i] = rg.Code
i++
}
h := Hey{
Regions: regions,
}
idxr := pm.idx.Root()
if idxr != cid.Undef {
h.IndexRoot = &idxr
}
return h
}
// RecordLatency for a given peer
func (pm *PeerMgr) recordLatency(p peer.ID, now, start time.Time) error {
pm.mu.Lock()
defer pm.mu.Unlock()
peer, ok := pm.peers[p]
if !ok {
return errors.New("no peer given ID")
}
peer.Latency = now.Sub(start)
pm.peers[p] = peer
return nil
}