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reactor.go
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reactor.go
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package mempool
import (
"context"
"errors"
"fmt"
"sync/atomic"
"time"
"golang.org/x/sync/semaphore"
abci "github.com/cometbft/cometbft/abci/types"
protomem "github.com/cometbft/cometbft/api/cometbft/mempool/v1"
cfg "github.com/cometbft/cometbft/config"
"github.com/cometbft/cometbft/internal/clist"
cmtsync "github.com/cometbft/cometbft/internal/sync"
"github.com/cometbft/cometbft/libs/log"
"github.com/cometbft/cometbft/p2p"
"github.com/cometbft/cometbft/types"
)
// Reactor handles mempool tx broadcasting amongst peers.
// It maintains a map from peer ID to counter, to prevent gossiping txs to the
// peers you received it from.
type Reactor struct {
p2p.BaseReactor
config *cfg.MempoolConfig
mempool *CListMempool
waitSync atomic.Bool
waitSyncCh chan struct{} // for signaling when to start receiving and sending txs
// `txSenders` maps every received transaction to the set of peer IDs that
// have sent the transaction to this node. Sender IDs are used during
// transaction propagation to avoid sending a transaction to a peer that
// already has it.
txSenders map[types.TxKey]map[p2p.ID]bool
txSendersMtx cmtsync.Mutex
// Semaphores to keep track of how many connections to peers are active for broadcasting
// transactions. Each semaphore has a capacity that puts an upper bound on the number of
// connections for different groups of peers.
activePersistentPeersSemaphore *semaphore.Weighted
activeNonPersistentPeersSemaphore *semaphore.Weighted
}
// NewReactor returns a new Reactor with the given config and mempool.
func NewReactor(config *cfg.MempoolConfig, mempool *CListMempool, waitSync bool) *Reactor {
memR := &Reactor{
config: config,
mempool: mempool,
waitSync: atomic.Bool{},
txSenders: make(map[types.TxKey]map[p2p.ID]bool),
}
memR.BaseReactor = *p2p.NewBaseReactor("Mempool", memR)
if waitSync {
memR.waitSync.Store(true)
memR.waitSyncCh = make(chan struct{})
}
memR.mempool.SetTxRemovedCallback(func(txKey types.TxKey) { memR.removeSenders(txKey) })
memR.activePersistentPeersSemaphore = semaphore.NewWeighted(int64(memR.config.ExperimentalMaxGossipConnectionsToPersistentPeers))
memR.activeNonPersistentPeersSemaphore = semaphore.NewWeighted(int64(memR.config.ExperimentalMaxGossipConnectionsToNonPersistentPeers))
return memR
}
// SetLogger sets the Logger on the reactor and the underlying mempool.
func (memR *Reactor) SetLogger(l log.Logger) {
memR.Logger = l
memR.mempool.SetLogger(l)
}
// OnStart implements p2p.BaseReactor.
func (memR *Reactor) OnStart() error {
if memR.WaitSync() {
memR.Logger.Info("Starting reactor in sync mode: tx propagation will start once sync completes")
}
if !memR.config.Broadcast {
memR.Logger.Info("Tx broadcasting is disabled")
}
return nil
}
// GetChannels implements Reactor by returning the list of channels for this
// reactor.
func (memR *Reactor) GetChannels() []*p2p.ChannelDescriptor {
largestTx := make([]byte, memR.config.MaxTxBytes)
batchMsg := protomem.Message{
Sum: &protomem.Message_Txs{
Txs: &protomem.Txs{Txs: [][]byte{largestTx}},
},
}
return []*p2p.ChannelDescriptor{
{
ID: MempoolChannel,
Priority: 5,
RecvMessageCapacity: batchMsg.Size(),
MessageType: &protomem.Message{},
},
}
}
// AddPeer implements Reactor.
// It starts a broadcast routine ensuring all txs are forwarded to the given peer.
func (memR *Reactor) AddPeer(peer p2p.Peer) {
if memR.config.Broadcast {
go func() {
// Always forward transactions to unconditional peers.
if !memR.Switch.IsPeerUnconditional(peer.ID()) {
// Depending on the type of peer, we choose a semaphore to limit the gossiping peers.
var peerSemaphore *semaphore.Weighted
if peer.IsPersistent() && memR.config.ExperimentalMaxGossipConnectionsToPersistentPeers > 0 {
peerSemaphore = memR.activePersistentPeersSemaphore
} else if !peer.IsPersistent() && memR.config.ExperimentalMaxGossipConnectionsToNonPersistentPeers > 0 {
peerSemaphore = memR.activeNonPersistentPeersSemaphore
}
if peerSemaphore != nil {
for peer.IsRunning() {
// Block on the semaphore until a slot is available to start gossiping with this peer.
// Do not block indefinitely, in case the peer is disconnected before gossiping starts.
ctxTimeout, cancel := context.WithTimeout(context.TODO(), 30*time.Second)
// Block sending transactions to peer until one of the connections become
// available in the semaphore.
err := peerSemaphore.Acquire(ctxTimeout, 1)
cancel()
if err != nil {
continue
}
// Release semaphore to allow other peer to start sending transactions.
defer peerSemaphore.Release(1)
break
}
}
}
memR.mempool.metrics.ActiveOutboundConnections.Add(1)
defer memR.mempool.metrics.ActiveOutboundConnections.Add(-1)
memR.broadcastTxRoutine(peer)
}()
}
}
// Receive implements Reactor.
// It adds any received transactions to the mempool.
func (memR *Reactor) Receive(e p2p.Envelope) {
memR.Logger.Debug("Receive", "src", e.Src, "chId", e.ChannelID, "msg", e.Message)
switch msg := e.Message.(type) {
case *protomem.Txs:
if memR.WaitSync() {
memR.Logger.Debug("Ignored message received while syncing", "msg", msg)
return
}
protoTxs := msg.GetTxs()
if len(protoTxs) == 0 {
memR.Logger.Error("received empty txs from peer", "src", e.Src)
return
}
for _, txBytes := range protoTxs {
tx := types.Tx(txBytes)
reqRes, err := memR.mempool.CheckTx(tx)
switch {
case errors.Is(err, ErrTxInCache):
memR.Logger.Debug("Tx already exists in cache", "tx", tx.Hash())
case err != nil:
memR.Logger.Info("Could not check tx", "tx", tx.Hash(), "err", err)
default:
// Record the sender only when the transaction is valid and, as
// a consequence, added to the mempool. Senders are stored until
// the transaction is removed from the mempool. Note that it's
// possible a tx is still in the cache but no longer in the
// mempool. For example, after committing a block, txs are
// removed from mempool but not the cache.
reqRes.SetCallback(func(res *abci.Response) {
if res.GetCheckTx().Code == abci.CodeTypeOK {
memR.addSender(tx.Key(), e.Src.ID())
}
})
}
}
default:
memR.Logger.Error("unknown message type", "src", e.Src, "chId", e.ChannelID, "msg", e.Message)
memR.Switch.StopPeerForError(e.Src, fmt.Errorf("mempool cannot handle message of type: %T", e.Message))
return
}
// broadcasting happens from go routines per peer
}
func (memR *Reactor) EnableInOutTxs() {
memR.Logger.Info("enabling inbound and outbound transactions")
if !memR.waitSync.CompareAndSwap(true, false) {
return
}
// Releases all the blocked broadcastTxRoutine instances.
if memR.config.Broadcast {
close(memR.waitSyncCh)
}
}
func (memR *Reactor) WaitSync() bool {
return memR.waitSync.Load()
}
// PeerState describes the state of a peer.
type PeerState interface {
GetHeight() int64
}
// Send new mempool txs to peer.
func (memR *Reactor) broadcastTxRoutine(peer p2p.Peer) {
var next *clist.CElement
// If the node is catching up, don't start this routine immediately.
if memR.WaitSync() {
select {
case <-memR.waitSyncCh:
// EnableInOutTxs() has set WaitSync() to false.
case <-memR.Quit():
return
}
}
for {
// In case of both next.NextWaitChan() and peer.Quit() are variable at the same time
if !memR.IsRunning() || !peer.IsRunning() {
return
}
// This happens because the CElement we were looking at got garbage
// collected (removed). That is, .NextWait() returned nil. Go ahead and
// start from the beginning.
if next == nil {
select {
case <-memR.mempool.TxsWaitChan(): // Wait until a tx is available
if next = memR.mempool.TxsFront(); next == nil {
continue
}
case <-peer.Quit():
return
case <-memR.Quit():
return
}
}
// Make sure the peer is up to date.
peerState, ok := peer.Get(types.PeerStateKey).(PeerState)
if !ok {
// Peer does not have a state yet. We set it in the consensus reactor, but
// when we add peer in Switch, the order we call reactors#AddPeer is
// different every time due to us using a map. Sometimes other reactors
// will be initialized before the consensus reactor. We should wait a few
// milliseconds and retry.
time.Sleep(PeerCatchupSleepIntervalMS * time.Millisecond)
continue
}
// If we suspect that the peer is lagging behind, at least by more than
// one block, we don't send the transaction immediately. This code
// reduces the mempool size and the recheck-tx rate of the receiving
// node. See [RFC 103] for an analysis on this optimization.
//
// [RFC 103]: https://github.com/cometbft/cometbft/pull/735
memTx := next.Value.(*mempoolTx)
if peerState.GetHeight() < memTx.Height()-1 {
time.Sleep(PeerCatchupSleepIntervalMS * time.Millisecond)
continue
}
// NOTE: Transaction batching was disabled due to
// https://github.com/tendermint/tendermint/issues/5796
if !memR.isSender(memTx.tx.Key(), peer.ID()) {
success := peer.Send(p2p.Envelope{
ChannelID: MempoolChannel,
Message: &protomem.Txs{Txs: [][]byte{memTx.tx}},
})
if !success {
time.Sleep(PeerCatchupSleepIntervalMS * time.Millisecond)
continue
}
}
select {
case <-next.NextWaitChan():
// see the start of the for loop for nil check
next = next.Next()
case <-peer.Quit():
return
case <-memR.Quit():
return
}
}
}
func (memR *Reactor) isSender(txKey types.TxKey, peerID p2p.ID) bool {
memR.txSendersMtx.Lock()
defer memR.txSendersMtx.Unlock()
sendersSet, ok := memR.txSenders[txKey]
return ok && sendersSet[peerID]
}
func (memR *Reactor) addSender(txKey types.TxKey, senderID p2p.ID) {
memR.txSendersMtx.Lock()
defer memR.txSendersMtx.Unlock()
if sendersSet, ok := memR.txSenders[txKey]; ok {
sendersSet[senderID] = true
return
}
memR.txSenders[txKey] = map[p2p.ID]bool{senderID: true}
}
func (memR *Reactor) removeSenders(txKey types.TxKey) {
memR.txSendersMtx.Lock()
defer memR.txSendersMtx.Unlock()
if memR.txSenders != nil {
delete(memR.txSenders, txKey)
}
}