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package p2p
import (
"context"
"fmt"
"io"
"sync"
"time"
"github.com/gogo/protobuf/proto"
"github.com/tendermint/tendermint/libs/log"
"github.com/tendermint/tendermint/libs/service"
)
// Router manages peer connections and routes messages between peers and reactor
// channels. This is an early prototype.
//
// Channels are registered via OpenChannel(). When called, we register an input
// message queue for the channel in channelQueues and spawn off a goroutine for
// Router.routeChannel(). This goroutine reads off outbound messages and puts
// them in the appropriate peer message queue, and processes peer errors which
// will close (and thus disconnect) the appriate peer queue. It runs until
// either the channel is closed by the caller or the router is stopped, at which
// point the input message queue is closed and removed.
//
// On startup, the router spawns off two primary goroutines that maintain
// connections to peers and run for the lifetime of the router:
//
// Router.dialPeers(): in a loop, asks the peerStore to dispense an
// eligible peer to connect to, and attempts to resolve and dial each
// address until successful.
//
// Router.acceptPeers(): in a loop, waits for the next inbound connection
// from a peer, and attempts to claim it in the peerStore.
//
// Once either an inbound or outbound connection has been made, an outbound
// message queue is registered in Router.peerQueues and a goroutine is spawned
// off for Router.routePeer() which will spawn off additional goroutines for
// Router.sendPeer() that sends outbound messages from the peer queue over the
// connection and for Router.receivePeer() that reads inbound messages from
// the connection and places them in the appropriate channel queue. When either
// goroutine exits, the connection and peer queue is closed, which will cause
// the other goroutines to close as well.
//
// The peerStore is used to coordinate peer connections, by only allowing a peer
// to be claimed (owned) by a single caller at a time (both for outbound and
// inbound connections). This is done either via peerStore.Dispense() which
// dispenses and claims an eligible peer to dial, or via peerStore.Claim() which
// attempts to claim a given peer for an inbound connection. Peers must be
// returned to the peerStore with peerStore.Return() to release the claim. Over
// time, the peerStore will also do peer scheduling and prioritization, e.g.
// ensuring we do exponential backoff on dial failures and connecting to
// more important peers first (such as persistent peers and validators).
//
// An additional goroutine Router.broadcastPeerUpdates() is also spawned off
// on startup, which consumes peer updates from Router.peerUpdatesCh (currently
// only connections and disconnections), and broadcasts them to all peer update
// subscriptions registered via SubscribePeerUpdates().
//
// On router shutdown, we close Router.stopCh which will signal to all
// goroutines to terminate. This in turn will cause all pending channel/peer
// queues to close, and we wait for this as a signal that goroutines have ended.
//
// All message scheduling should be limited to the queue implementations used
// for channel queues and peer queues. All message sending throughout the router
// is blocking, and if any messages should be dropped or buffered this is the
// sole responsibility of the queue, such that we can limit this logic to a
// single place. There is currently only a FIFO queue implementation that always
// blocks and never drops messages, but this must be improved with other
// implementations. The only exception is that all message sending must also
// select on appropriate channel/queue/router closure signals, to avoid blocking
// forever on a channel that has no consumer.
type Router struct {
*service.BaseService
logger log.Logger
transports map[Protocol]Transport
peerManager *peerManager
// FIXME: Consider using sync.Map.
peerMtx sync.RWMutex
peerQueues map[NodeID]queue
// FIXME: We don't strictly need to use a mutex for this if we seal the
// channels on router start. This depends on whether we want to allow
// dynamic channels in the future.
channelMtx sync.RWMutex
channelQueues map[ChannelID]queue
channelMessages map[ChannelID]proto.Message
// stopCh is used to signal router shutdown, by closing the channel.
stopCh chan struct{}
}
// NewRouter creates a new Router, dialing the given peers.
//
// FIXME: providing protocol/transport maps is cumbersome in tests, we should
// consider adding Protocols() to the Transport interface instead and register
// protocol/transport mappings automatically on a first-come basis.
func NewRouter(logger log.Logger, transports map[Protocol]Transport, peers []PeerAddress) *Router {
router := &Router{
logger: logger,
transports: transports,
peerManager: newPeerManager(newPeerStore()),
stopCh: make(chan struct{}),
channelQueues: map[ChannelID]queue{},
channelMessages: map[ChannelID]proto.Message{},
peerQueues: map[NodeID]queue{},
}
router.BaseService = service.NewBaseService(logger, "router", router)
for _, address := range peers {
if err := router.peerManager.Add(address); err != nil {
logger.Error("failed to add peer", "address", address, "err", err)
}
}
return router
}
// OpenChannel opens a new channel for the given message type. The caller must
// close the channel when done, and this must happen before the router stops.
func (r *Router) OpenChannel(id ChannelID, messageType proto.Message) (*Channel, error) {
// FIXME: NewChannel should take directional channels so we can pass
// queue.dequeue() instead of reaching inside for queue.queueCh.
queue := newFIFOQueue()
channel := NewChannel(id, messageType, queue.queueCh, make(chan Envelope), make(chan PeerError))
r.channelMtx.Lock()
defer r.channelMtx.Unlock()
if _, ok := r.channelQueues[id]; ok {
return nil, fmt.Errorf("channel %v already exists", id)
}
r.channelQueues[id] = queue
r.channelMessages[id] = messageType
go func() {
defer func() {
r.channelMtx.Lock()
delete(r.channelQueues, id)
delete(r.channelMessages, id)
r.channelMtx.Unlock()
queue.close()
}()
r.routeChannel(channel)
}()
return channel, nil
}
// routeChannel receives outbound messages and errors from a channel and routes
// them to the appropriate peer. It returns when either the channel is closed or
// the router is shutting down.
func (r *Router) routeChannel(channel *Channel) {
for {
select {
case envelope, ok := <-channel.outCh:
if !ok {
return
}
// FIXME: This is a bit unergonomic, maybe it'd be better for Wrap()
// to return a wrapped copy.
if _, ok := channel.messageType.(Wrapper); ok {
wrapper := proto.Clone(channel.messageType)
if err := wrapper.(Wrapper).Wrap(envelope.Message); err != nil {
r.Logger.Error("failed to wrap message", "err", err)
continue
}
envelope.Message = wrapper
}
envelope.channelID = channel.id
if envelope.Broadcast {
r.peerMtx.RLock()
peerQueues := make(map[NodeID]queue, len(r.peerQueues))
for peerID, peerQueue := range r.peerQueues {
peerQueues[peerID] = peerQueue
}
r.peerMtx.RUnlock()
for peerID, peerQueue := range peerQueues {
e := envelope
e.Broadcast = false
e.To = peerID
select {
case peerQueue.enqueue() <- e:
case <-peerQueue.closed():
case <-r.stopCh:
return
}
}
} else {
r.peerMtx.RLock()
peerQueue, ok := r.peerQueues[envelope.To]
r.peerMtx.RUnlock()
if !ok {
r.logger.Error("dropping message for non-connected peer",
"peer", envelope.To, "channel", channel.id)
continue
}
select {
case peerQueue.enqueue() <- envelope:
case <-peerQueue.closed():
r.logger.Error("dropping message for non-connected peer",
"peer", envelope.To, "channel", channel.id)
case <-r.stopCh:
return
}
}
case peerError, ok := <-channel.errCh:
if !ok {
return
}
// FIXME: We just disconnect the peer for now
r.logger.Error("peer error, disconnecting", "peer", peerError.PeerID, "err", peerError.Err)
r.peerMtx.RLock()
peerQueue, ok := r.peerQueues[peerError.PeerID]
r.peerMtx.RUnlock()
if ok {
peerQueue.close()
}
case <-channel.Done():
return
case <-r.stopCh:
return
}
}
}
// acceptPeers accepts inbound connections from peers on the given transport.
func (r *Router) acceptPeers(transport Transport) {
for {
select {
case <-r.stopCh:
return
default:
}
conn, err := transport.Accept(context.Background())
switch err {
case nil:
case ErrTransportClosed{}, io.EOF:
r.logger.Info("transport closed; stopping accept routine", "transport", transport)
return
default:
r.logger.Error("failed to accept connection", "transport", transport, "err", err)
continue
}
go func() {
defer func() {
_ = conn.Close()
}()
peerID := conn.NodeInfo().NodeID
if err := r.peerManager.Accepted(peerID); err != nil {
r.logger.Error("failed to accept connection", "peer", peerID, "err", err)
return
}
queue := newFIFOQueue()
r.peerMtx.Lock()
r.peerQueues[peerID] = queue
r.peerMtx.Unlock()
r.peerManager.Ready(peerID)
defer func() {
r.peerMtx.Lock()
delete(r.peerQueues, peerID)
r.peerMtx.Unlock()
queue.close()
if err := r.peerManager.Disconnected(peerID); err != nil {
r.logger.Error("failed to disconnect peer", "peer", peerID, "err", err)
}
}()
r.routePeer(peerID, conn, queue)
}()
}
}
// dialPeers maintains outbound connections to peers.
func (r *Router) dialPeers() {
for {
select {
case <-r.stopCh:
return
default:
}
peerID, address, err := r.peerManager.DialNext()
if err != nil {
r.logger.Error("failed to find next peer to dial", "err", err)
return
} else if peerID == "" {
r.logger.Debug("no eligible peers, sleeping")
select {
case <-time.After(time.Second):
continue
case <-r.stopCh:
return
}
}
go func() {
conn, err := r.dialPeer(address)
if err != nil {
r.logger.Error("failed to dial peer, will retry", "peer", peerID)
if err = r.peerManager.DialFailed(peerID, address); err != nil {
r.logger.Error("failed to report dial failure", "peer", peerID, "err", err)
}
return
}
defer conn.Close()
if err = r.peerManager.Dialed(peerID, address); err != nil {
r.logger.Error("failed to dial peer", "peer", peerID, "err", err)
return
}
queue := newFIFOQueue()
r.peerMtx.Lock()
r.peerQueues[peerID] = queue
r.peerMtx.Unlock()
r.peerManager.Ready(peerID)
defer func() {
r.peerMtx.Lock()
delete(r.peerQueues, peerID)
r.peerMtx.Unlock()
queue.close()
if err := r.peerManager.Disconnected(peerID); err != nil {
r.logger.Error("failed to disconnect peer", "peer", peerID, "err", err)
}
}()
r.routePeer(peerID, conn, queue)
}()
}
}
// dialPeer attempts to connect to a peer.
func (r *Router) dialPeer(address PeerAddress) (Connection, error) {
ctx := context.Background()
resolveCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
defer cancel()
r.logger.Info("resolving peer address", "address", address)
endpoints, err := address.Resolve(resolveCtx)
if err != nil {
return nil, fmt.Errorf("failed to resolve address %q: %w", address, err)
}
for _, endpoint := range endpoints {
t, ok := r.transports[endpoint.Protocol]
if !ok {
r.logger.Error("no transport found for protocol", "protocol", endpoint.Protocol)
continue
}
dialCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
defer cancel()
conn, err := t.Dial(dialCtx, endpoint)
if err != nil {
r.logger.Error("failed to dial endpoint", "endpoint", endpoint)
} else {
r.logger.Info("connected to peer", "peer", address.NodeID(), "endpoint", endpoint)
return conn, nil
}
}
return nil, fmt.Errorf("failed to connect to peer via %q", address)
}
// routePeer routes inbound messages from a peer to channels, and also sends
// outbound queued messages to the peer. It will close the connection and send
// queue, using this as a signal to coordinate the internal receivePeer() and
// sendPeer() goroutines. It blocks until the peer is done, e.g. when the
// connection or queue is closed.
func (r *Router) routePeer(peerID NodeID, conn Connection, sendQueue queue) {
r.logger.Info("routing peer", "peer", peerID)
resultsCh := make(chan error, 2)
go func() {
resultsCh <- r.receivePeer(peerID, conn)
}()
go func() {
resultsCh <- r.sendPeer(peerID, conn, sendQueue)
}()
err := <-resultsCh
_ = conn.Close()
sendQueue.close()
if e := <-resultsCh; err == nil {
// The first err was nil, so we update it with the second result,
// which may or may not be nil.
err = e
}
switch err {
case nil, io.EOF, ErrTransportClosed{}:
r.logger.Info("peer disconnected", "peer", peerID)
default:
r.logger.Error("peer failure", "peer", peerID, "err", err)
}
}
// receivePeer receives inbound messages from a peer, deserializes them and
// passes them on to the appropriate channel.
func (r *Router) receivePeer(peerID NodeID, conn Connection) error {
for {
chID, bz, err := conn.ReceiveMessage()
if err != nil {
return err
}
r.channelMtx.RLock()
queue, ok := r.channelQueues[ChannelID(chID)]
messageType := r.channelMessages[ChannelID(chID)]
r.channelMtx.RUnlock()
if !ok {
r.logger.Error("dropping message for unknown channel", "peer", peerID, "channel", chID)
continue
}
msg := proto.Clone(messageType)
if err := proto.Unmarshal(bz, msg); err != nil {
r.logger.Error("message decoding failed, dropping message", "peer", peerID, "err", err)
continue
}
if wrapper, ok := msg.(Wrapper); ok {
msg, err = wrapper.Unwrap()
if err != nil {
r.logger.Error("failed to unwrap message", "err", err)
continue
}
}
select {
// FIXME: ReceiveMessage() should return ChannelID.
case queue.enqueue() <- Envelope{channelID: ChannelID(chID), From: peerID, Message: msg}:
r.logger.Debug("received message", "peer", peerID, "message", msg)
case <-queue.closed():
r.logger.Error("channel closed, dropping message", "peer", peerID, "channel", chID)
case <-r.stopCh:
return nil
}
}
}
// sendPeer sends queued messages to a peer.
func (r *Router) sendPeer(peerID NodeID, conn Connection, queue queue) error {
for {
select {
case envelope := <-queue.dequeue():
bz, err := proto.Marshal(envelope.Message)
if err != nil {
r.logger.Error("failed to marshal message", "peer", peerID, "err", err)
continue
}
// FIXME: SendMessage() should take ChannelID.
_, err = conn.SendMessage(byte(envelope.channelID), bz)
if err != nil {
return err
}
r.logger.Debug("sent message", "peer", envelope.To, "message", envelope.Message)
case <-queue.closed():
return nil
case <-r.stopCh:
return nil
}
}
}
// SubscribePeerUpdates creates a new peer updates subscription. The caller must
// consume the peer updates in a timely fashion and close the subscription when
// done, since delivery is guaranteed and will block peer
// connection/disconnection otherwise.
//
// FIXME: Consider having callers just use peerManager.Subscribe() directly, if
// we export peerManager and make it an injected dependency (which we probably
// should).
func (r *Router) SubscribePeerUpdates() *PeerUpdatesCh {
return r.peerManager.Subscribe()
}
// OnStart implements service.Service.
func (r *Router) OnStart() error {
go r.dialPeers()
for _, transport := range r.transports {
go r.acceptPeers(transport)
}
return nil
}
// OnStop implements service.Service.
func (r *Router) OnStop() {
// Collect all active queues, so we can wait for them to close.
queues := []queue{}
r.channelMtx.RLock()
for _, q := range r.channelQueues {
queues = append(queues, q)
}
r.channelMtx.RUnlock()
r.peerMtx.RLock()
for _, q := range r.peerQueues {
queues = append(queues, q)
}
r.peerMtx.RUnlock()
// Signal router shutdown, and wait for queues (and thus goroutines)
// to complete.
close(r.stopCh)
for _, q := range queues {
<-q.closed()
}
}