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eth: stabilize tx relay peer selection #31714

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eth: stabilize tx relay peer selection #31714

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813799b
eth: stabilize peer selection for transaction broadcast
cskiraly Apr 24, 2025
55db2f3
eth: use hysteresis to stabilize peer selection for transaction broad…
cskiraly Apr 25, 2025
6fed129
eth: simplify bigInt usage in BroadcastTransactions
cskiraly Apr 29, 2025
1e0d394
eth/handler: fix unaligned 64-bit atomic operation error
cskiraly Apr 29, 2025
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30 changes: 22 additions & 8 deletions eth/handler.go
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Original file line number Diff line number Diff line change
Expand Up @@ -52,6 +52,9 @@ const (
// All transactions with a higher size will be announced and need to be fetched
// by the peer.
txMaxBroadcastSize = 4096

// Hysteresis to stabilize the number of direct peers to send transactions to.
directPeersHysteresis = 0.5
)

var syncChallengeTimeout = 15 * time.Second // Time allowance for a node to reply to the sync progress challenge
Expand Down Expand Up @@ -110,10 +113,11 @@ type handler struct {
snapSync atomic.Bool // Flag whether snap sync is enabled (gets disabled if we already have blocks)
synced atomic.Bool // Flag whether we're considered synchronised (enables transaction processing)

database ethdb.Database
txpool txPool
chain *core.BlockChain
maxPeers int
database ethdb.Database
txpool txPool
chain *core.BlockChain
maxPeers int
lastDirect atomic.Int64 // Last number of peers we sent transactions to, used to stabilize the randomness

downloader *downloader.Downloader
txFetcher *fetcher.TxFetcher
Expand Down Expand Up @@ -477,11 +481,21 @@ func (h *handler) BroadcastTransactions(txs types.Transactions) {
annos = make(map[*ethPeer][]common.Hash) // Set peer->hash to announce
)
// Broadcast transactions to a batch of peers not knowing about it
direct := big.NewInt(int64(math.Sqrt(float64(h.peers.len())))) // Approximate number of peers to broadcast to
if direct.BitLen() == 0 {
direct = big.NewInt(1)
sqrtPeers := math.Sqrt(float64(h.peers.len())) // Approximate number of peers to broadcast to

// Use some hysteresis to avoid oscillating between two values, stabilising the modulus in the peer selection
// If the number of peers is small, use a minimum of 1 peer
var directInt int64
lastDirect := h.lastDirect.Load()
if int64(sqrtPeers) >= lastDirect {
directInt = max(int64(sqrtPeers), 1)
} else {
directInt = max(min(int64(sqrtPeers+directPeersHysteresis), lastDirect), 1)
}
total := new(big.Int).Exp(direct, big.NewInt(2), nil) // Stabilise total peer count a bit based on sqrt peers
h.lastDirect.Store(directInt)

direct := big.NewInt(directInt) // Number of peers to send directly to
total := big.NewInt(directInt * directInt) // Stabilise total peer count a bit based on sqrt peers

var (
signer = types.LatestSigner(h.chain.Config()) // Don't care about chain status, we just need *a* sender
Expand Down