network: retransmit stale transactions

pkg/core/mempool/mem_pool.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"math/big"
+	"math/bits"
 	"sort"
 	"sync"
 
@@ -58,6 +59,9 @@ type Pool struct {
 
 	capacity   int
 	feePerByte int64
+
+	resendThreshold uint32
+	resendFunc      func(*transaction.Transaction)
 }
 
 func (p items) Len() int           { return len(p) }
@@ -289,6 +293,8 @@ func (mp *Pool) RemoveStale(isOK func(*transaction.Transaction) bool, feer Feer)
 	if feer.P2PSigExtensionsEnabled() {
 		mp.conflicts = make(map[util.Uint256][]util.Uint256)
 	}
+	height := feer.BlockHeight()
+	var staleTxs []*transaction.Transaction
 	for _, itm := range mp.verifiedTxes {
 		if isOK(itm.txn) && mp.checkPolicy(itm.txn, policyChanged) && mp.tryAddSendersFee(itm.txn, feer, true) {
 			newVerifiedTxes = append(newVerifiedTxes, itm)
@@ -298,10 +304,21 @@ func (mp *Pool) RemoveStale(isOK func(*transaction.Transaction) bool, feer Feer)
 					mp.conflicts[hash] = append(mp.conflicts[hash], itm.txn.Hash())
 				}
 			}
+			if mp.resendThreshold != 0 {
+				// tx is resend at resendThreshold, 2*resendThreshold, 4*resendThreshold ...
+				// so quotient must be a power of two.
+				diff := (height - itm.blockStamp)
+				if diff%mp.resendThreshold == 0 && bits.OnesCount32(diff/mp.resendThreshold) == 1 {
+					staleTxs = append(staleTxs, itm.txn)
+				}
+			}
 		} else {
 			delete(mp.verifiedMap, itm.txn.Hash())
 		}
 	}
+	if len(staleTxs) != 0 {
+		go mp.resendStaleTxs(staleTxs)
+	}
 	mp.verifiedTxes = newVerifiedTxes
 	mp.lock.Unlock()
 }
@@ -336,6 +353,21 @@ func New(capacity int) *Pool {
 	}
 }
 
+// SetResendThreshold sets threshold after which transaction will be considered stale
+// and returned for retransmission by `GetStaleTransactions`.
+func (mp *Pool) SetResendThreshold(h uint32, f func(*transaction.Transaction)) {
+	mp.lock.Lock()
+	defer mp.lock.Unlock()
+	mp.resendThreshold = h
+	mp.resendFunc = f
+}
+
+func (mp *Pool) resendStaleTxs(txs []*transaction.Transaction) {
+	for i := range txs {
+		mp.resendFunc(txs[i])
+	}
+}
+
 // TryGetValue returns a transaction and its fee if it exists in the memory pool.
 func (mp *Pool) TryGetValue(hash util.Uint256) (*transaction.Transaction, bool) {
 	mp.lock.RLock()

pkg/core/mempool/mem_pool_test.go

@@ -5,6 +5,7 @@ import (
 	"math/big"
 	"sort"
 	"testing"
+	"time"
 
 	"github.com/nspcc-dev/neo-go/pkg/config/netmode"
 	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
@@ -16,8 +17,9 @@ import (
 )
 
 type FeerStub struct {
-	feePerByte int64
-	p2pSigExt  bool
+	feePerByte  int64
+	p2pSigExt   bool
+	blockHeight uint32
 }
 
 var balance = big.NewInt(10000000)
@@ -27,7 +29,7 @@ func (fs *FeerStub) FeePerByte() int64 {
 }
 
 func (fs *FeerStub) BlockHeight() uint32 {
-	return 0
+	return fs.blockHeight
 }
 
 func (fs *FeerStub) GetUtilityTokenBalance(uint160 util.Uint160) *big.Int {
@@ -59,6 +61,50 @@ func testMemPoolAddRemoveWithFeer(t *testing.T, fs Feer) {
 	assert.Equal(t, 0, len(mp.verifiedTxes))
 }
 
+func TestMemPoolRemoveStale(t *testing.T) {
+	mp := New(5)
+	txs := make([]*transaction.Transaction, 5)
+	for i := range txs {
+		txs[i] = transaction.New(netmode.UnitTestNet, []byte{byte(opcode.PUSH1)}, 0)
+		txs[i].Nonce = uint32(i)
+		txs[i].Signers = []transaction.Signer{{Account: util.Uint160{1, 2, 3}}}
+		require.NoError(t, mp.Add(txs[i], &FeerStub{blockHeight: uint32(i)}))
+	}
+
+	staleTxs := make(chan *transaction.Transaction, 5)
+	f := func(tx *transaction.Transaction) {
+		staleTxs <- tx
+	}
+	mp.SetResendThreshold(5, f)
+
+	isValid := func(tx *transaction.Transaction) bool {
+		return tx.Nonce%2 == 0
+	}
+
+	mp.RemoveStale(isValid, &FeerStub{blockHeight: 5}) // 0 + 5
+	require.Eventually(t, func() bool { return len(staleTxs) == 1 }, time.Second, time.Millisecond*100)
+	require.Equal(t, txs[0], <-staleTxs)
+
+	mp.RemoveStale(isValid, &FeerStub{blockHeight: 7}) // 2 + 5
+	require.Eventually(t, func() bool { return len(staleTxs) == 1 }, time.Second, time.Millisecond*100)
+	require.Equal(t, txs[2], <-staleTxs)
+
+	mp.RemoveStale(isValid, &FeerStub{blockHeight: 10}) // 0 + 2 * 5
+	require.Eventually(t, func() bool { return len(staleTxs) == 1 }, time.Second, time.Millisecond*100)
+	require.Equal(t, txs[0], <-staleTxs)
+
+	mp.RemoveStale(isValid, &FeerStub{blockHeight: 15}) // 0 + 3 * 5
+
+	// tx[2] should appear, so it is also checked that tx[0] wasn't sent on height 15.
+	mp.RemoveStale(isValid, &FeerStub{blockHeight: 22}) // 2 + 4 * 5
+	require.Eventually(t, func() bool { return len(staleTxs) == 1 }, time.Second, time.Millisecond*100)
+	require.Equal(t, txs[2], <-staleTxs)
+
+	// panic if something is sent after this.
+	close(staleTxs)
+	require.Len(t, staleTxs, 0)
+}
+
 func TestMemPoolAddRemove(t *testing.T) {
 	var fs = &FeerStub{}
 	testMemPoolAddRemoveWithFeer(t, fs)

pkg/network/server.go

@@ -171,6 +171,7 @@ func (s *Server) Start(errChan chan error) {
 		zap.Uint32("headerHeight", s.chain.HeaderHeight()))
 
 	s.tryStartConsensus()
+	s.initStaleTxMemPool()
 
 	go s.broadcastTxLoop()
 	go s.relayBlocksLoop()
@@ -905,6 +906,18 @@ func (s *Server) broadcastTxHashes(hs []util.Uint256) {
 	s.iteratePeersWithSendMsg(msg, Peer.EnqueuePacket, Peer.IsFullNode)
 }
 
+// initStaleTxMemPool initializes mempool for stale tx processing.
+func (s *Server) initStaleTxMemPool() {
+	cfg := s.chain.GetConfig()
+	threshold := 5
+	if cfg.ValidatorsCount*2 > threshold {
+		threshold = cfg.ValidatorsCount * 2
+	}
+
+	mp := s.chain.GetMemPool()
+	mp.SetResendThreshold(uint32(threshold), s.broadcastTX)
+}
+
 // broadcastTxLoop is a loop for batching and sending
 // transactions hashes in an INV payload.
 func (s *Server) broadcastTxLoop() {