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topic.go
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topic.go
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package pubsub
import (
"context"
"errors"
"fmt"
"sync"
"time"
pb "github.com/libp2p/go-libp2p-pubsub/pb"
"github.com/libp2p/go-libp2p/core/crypto"
"github.com/libp2p/go-libp2p/core/peer"
)
// ErrTopicClosed is returned if a Topic is utilized after it has been closed
var ErrTopicClosed = errors.New("this Topic is closed, try opening a new one")
// ErrNilSignKey is returned if a nil private key was provided
var ErrNilSignKey = errors.New("nil sign key")
// ErrEmptyPeerID is returned if an empty peer ID was provided
var ErrEmptyPeerID = errors.New("empty peer ID")
// Topic is the handle for a pubsub topic
type Topic struct {
p *PubSub
topic string
evtHandlerMux sync.RWMutex
evtHandlers map[*TopicEventHandler]struct{}
mux sync.RWMutex
closed bool
}
// String returns the topic associated with t
func (t *Topic) String() string {
return t.topic
}
// SetScoreParams sets the topic score parameters if the pubsub router supports peer
// scoring
func (t *Topic) SetScoreParams(p *TopicScoreParams) error {
err := p.validate()
if err != nil {
return fmt.Errorf("invalid topic score parameters: %w", err)
}
t.mux.Lock()
defer t.mux.Unlock()
if t.closed {
return ErrTopicClosed
}
result := make(chan error, 1)
update := func() {
gs, ok := t.p.rt.(*GossipSubRouter)
if !ok {
result <- fmt.Errorf("pubsub router is not gossipsub")
return
}
if gs.score == nil {
result <- fmt.Errorf("peer scoring is not enabled in router")
return
}
err := gs.score.SetTopicScoreParams(t.topic, p)
result <- err
}
select {
case t.p.eval <- update:
err = <-result
return err
case <-t.p.ctx.Done():
return t.p.ctx.Err()
}
}
// EventHandler creates a handle for topic specific events
// Multiple event handlers may be created and will operate independently of each other
func (t *Topic) EventHandler(opts ...TopicEventHandlerOpt) (*TopicEventHandler, error) {
t.mux.RLock()
defer t.mux.RUnlock()
if t.closed {
return nil, ErrTopicClosed
}
h := &TopicEventHandler{
topic: t,
err: nil,
evtLog: make(map[peer.ID]EventType),
evtLogCh: make(chan struct{}, 1),
}
for _, opt := range opts {
err := opt(h)
if err != nil {
return nil, err
}
}
done := make(chan struct{}, 1)
select {
case t.p.eval <- func() {
tmap := t.p.topics[t.topic]
for p := range tmap {
h.evtLog[p] = PeerJoin
}
t.evtHandlerMux.Lock()
t.evtHandlers[h] = struct{}{}
t.evtHandlerMux.Unlock()
done <- struct{}{}
}:
case <-t.p.ctx.Done():
return nil, t.p.ctx.Err()
}
<-done
return h, nil
}
func (t *Topic) sendNotification(evt PeerEvent) {
t.evtHandlerMux.RLock()
defer t.evtHandlerMux.RUnlock()
for h := range t.evtHandlers {
h.sendNotification(evt)
}
}
// Subscribe returns a new Subscription for the topic.
// Note that subscription is not an instantaneous operation. It may take some time
// before the subscription is processed by the pubsub main loop and propagated to our peers.
func (t *Topic) Subscribe(opts ...SubOpt) (*Subscription, error) {
t.mux.RLock()
defer t.mux.RUnlock()
if t.closed {
return nil, ErrTopicClosed
}
sub := &Subscription{
topic: t.topic,
ctx: t.p.ctx,
}
for _, opt := range opts {
err := opt(sub)
if err != nil {
return nil, err
}
}
if sub.ch == nil {
// apply the default size
sub.ch = make(chan *Message, 32)
}
out := make(chan *Subscription, 1)
t.p.disc.Discover(sub.topic)
select {
case t.p.addSub <- &addSubReq{
sub: sub,
resp: out,
}:
case <-t.p.ctx.Done():
return nil, t.p.ctx.Err()
}
return <-out, nil
}
// Relay enables message relaying for the topic and returns a reference
// cancel function. Subsequent calls increase the reference counter.
// To completely disable the relay, all references must be cancelled.
func (t *Topic) Relay() (RelayCancelFunc, error) {
t.mux.RLock()
defer t.mux.RUnlock()
if t.closed {
return nil, ErrTopicClosed
}
out := make(chan RelayCancelFunc, 1)
t.p.disc.Discover(t.topic)
select {
case t.p.addRelay <- &addRelayReq{
topic: t.topic,
resp: out,
}:
case <-t.p.ctx.Done():
return nil, t.p.ctx.Err()
}
return <-out, nil
}
// RouterReady is a function that decides if a router is ready to publish
type RouterReady func(rt PubSubRouter, topic string) (bool, error)
// ProvideKey is a function that provides a private key and its associated peer ID when publishing a new message
type ProvideKey func() (crypto.PrivKey, peer.ID)
type PublishOptions struct {
ready RouterReady
customKey ProvideKey
local bool
}
type PubOpt func(pub *PublishOptions) error
// Publish publishes data to topic.
func (t *Topic) Publish(ctx context.Context, data []byte, opts ...PubOpt) error {
t.mux.RLock()
defer t.mux.RUnlock()
if t.closed {
return ErrTopicClosed
}
pid := t.p.signID
key := t.p.signKey
pub := &PublishOptions{}
for _, opt := range opts {
err := opt(pub)
if err != nil {
return err
}
}
if pub.customKey != nil {
key, pid = pub.customKey()
if key == nil {
return ErrNilSignKey
}
if len(pid) == 0 {
return ErrEmptyPeerID
}
}
m := &pb.Message{
Data: data,
Topic: &t.topic,
From: nil,
Seqno: nil,
}
if pid != "" {
m.From = []byte(pid)
m.Seqno = t.p.nextSeqno()
}
if key != nil {
m.From = []byte(pid)
err := signMessage(pid, key, m)
if err != nil {
return err
}
}
if pub.ready != nil {
if t.p.disc.discovery != nil {
t.p.disc.Bootstrap(ctx, t.topic, pub.ready)
} else {
// TODO: we could likely do better than polling every 200ms.
// For example, block this goroutine on a channel,
// and check again whenever events tell us that the number of
// peers has increased.
var ticker *time.Ticker
readyLoop:
for {
// Check if ready for publishing.
// Similar to what disc.Bootstrap does.
res := make(chan bool, 1)
select {
case t.p.eval <- func() {
done, _ := pub.ready(t.p.rt, t.topic)
res <- done
}:
if <-res {
break readyLoop
}
case <-t.p.ctx.Done():
return t.p.ctx.Err()
case <-ctx.Done():
return ctx.Err()
}
if ticker == nil {
ticker = time.NewTicker(200 * time.Millisecond)
defer ticker.Stop()
}
select {
case <-ticker.C:
case <-ctx.Done():
return fmt.Errorf("router is not ready: %w", ctx.Err())
}
}
}
}
return t.p.val.PushLocal(&Message{m, "", t.p.host.ID(), nil, pub.local})
}
// WithReadiness returns a publishing option for only publishing when the router is ready.
// This option is not useful unless PubSub is also using WithDiscovery
func WithReadiness(ready RouterReady) PubOpt {
return func(pub *PublishOptions) error {
pub.ready = ready
return nil
}
}
// WithLocalPublication returns a publishing option to notify in-process subscribers only.
// It prevents message publication to mesh peers.
// Useful in edge cases where the msg needs to be only delivered to the in-process subscribers,
// e.g. not to spam the network with outdated msgs.
// Should not be used specifically for in-process pubsubing.
func WithLocalPublication(local bool) PubOpt {
return func(pub *PublishOptions) error {
pub.local = local
return nil
}
}
// WithSecretKeyAndPeerId returns a publishing option for providing a custom private key and its corresponding peer ID
// This option is useful when we want to send messages from "virtual", never-connectable peers in the network
func WithSecretKeyAndPeerId(key crypto.PrivKey, pid peer.ID) PubOpt {
return func(pub *PublishOptions) error {
pub.customKey = func() (crypto.PrivKey, peer.ID) {
return key, pid
}
return nil
}
}
// Close closes down the topic. Will return an error unless there are no active event handlers or subscriptions.
// Does not error if the topic is already closed.
func (t *Topic) Close() error {
t.mux.Lock()
defer t.mux.Unlock()
if t.closed {
return nil
}
req := &rmTopicReq{t, make(chan error, 1)}
select {
case t.p.rmTopic <- req:
case <-t.p.ctx.Done():
return t.p.ctx.Err()
}
err := <-req.resp
if err == nil {
t.closed = true
}
return err
}
// ListPeers returns a list of peers we are connected to in the given topic.
func (t *Topic) ListPeers() []peer.ID {
t.mux.RLock()
defer t.mux.RUnlock()
if t.closed {
return []peer.ID{}
}
return t.p.ListPeers(t.topic)
}
type EventType int
const (
PeerJoin EventType = iota
PeerLeave
)
// TopicEventHandler is used to manage topic specific events. No Subscription is required to receive events.
type TopicEventHandler struct {
topic *Topic
err error
evtLogMx sync.Mutex
evtLog map[peer.ID]EventType
evtLogCh chan struct{}
}
type TopicEventHandlerOpt func(t *TopicEventHandler) error
type PeerEvent struct {
Type EventType
Peer peer.ID
}
// Cancel closes the topic event handler
func (t *TopicEventHandler) Cancel() {
topic := t.topic
t.err = fmt.Errorf("topic event handler cancelled by calling handler.Cancel()")
topic.evtHandlerMux.Lock()
delete(topic.evtHandlers, t)
t.topic.evtHandlerMux.Unlock()
}
func (t *TopicEventHandler) sendNotification(evt PeerEvent) {
t.evtLogMx.Lock()
t.addToEventLog(evt)
t.evtLogMx.Unlock()
}
// addToEventLog assumes a lock has been taken to protect the event log
func (t *TopicEventHandler) addToEventLog(evt PeerEvent) {
e, ok := t.evtLog[evt.Peer]
if !ok {
t.evtLog[evt.Peer] = evt.Type
// send signal that an event has been added to the event log
select {
case t.evtLogCh <- struct{}{}:
default:
}
} else if e != evt.Type {
delete(t.evtLog, evt.Peer)
}
}
// pullFromEventLog assumes a lock has been taken to protect the event log
func (t *TopicEventHandler) pullFromEventLog() (PeerEvent, bool) {
for k, v := range t.evtLog {
evt := PeerEvent{Peer: k, Type: v}
delete(t.evtLog, k)
return evt, true
}
return PeerEvent{}, false
}
// NextPeerEvent returns the next event regarding subscribed peers
// Guarantees: Peer Join and Peer Leave events for a given peer will fire in order.
// Unless a peer both Joins and Leaves before NextPeerEvent emits either event
// all events will eventually be received from NextPeerEvent.
func (t *TopicEventHandler) NextPeerEvent(ctx context.Context) (PeerEvent, error) {
for {
t.evtLogMx.Lock()
evt, ok := t.pullFromEventLog()
if ok {
// make sure an event log signal is available if there are events in the event log
if len(t.evtLog) > 0 {
select {
case t.evtLogCh <- struct{}{}:
default:
}
}
t.evtLogMx.Unlock()
return evt, nil
}
t.evtLogMx.Unlock()
select {
case <-t.evtLogCh:
continue
case <-ctx.Done():
return PeerEvent{}, ctx.Err()
}
}
}