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p2p: make dial faster by streamlined discovery process #31678

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cskiraly wants to merge 2 commits into from
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p2p: make dial faster by streamlined discovery process #31678

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7bebcd1
eth: add multiple parallel lookup in discovery
cskiraly Apr 29, 2025
e5af7d1
eth: reduce parallel lookups to 2
cskiraly Aug 15, 2025
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35 changes: 26 additions & 9 deletions eth/backend.go
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Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,15 @@ const (
// We expect a normal source to produce ~10 candidates per second.
discmixTimeout = 100 * time.Millisecond

// discoveryParallelLookups is the number of parallel lookups to perform by DHT
// sources (disc/v4 and disc/v5). We set this number large enough to be able to
// feed the dial queue with enough peers. Since the whole discovery process is triggered
// only when dial candidates are needed, we can keep this number high without worrying
// about overloading the DHT. Only caveat is that in a small network, where maxpeers is
// higher than the actual number of nodes, this may lead to continuous lookups. We don't
// yet have a self-tuning solution for this, so we keep the value at 2.
discoveryParallelLookups = 2

// discoveryPrefetchBuffer is the number of peers to pre-fetch from a discovery
// source. It is useful to avoid the negative effects of potential longer timeouts
// in the discovery, keeping dial progress while waiting for the next batch of
Expand Down Expand Up @@ -532,26 +541,34 @@ func (s *Ethereum) setupDiscovery() error {

// Add DHT nodes from discv4.
if s.p2pServer.DiscoveryV4() != nil {
iter := s.p2pServer.DiscoveryV4().RandomNodes()
resolverFunc := func(ctx context.Context, enr *enode.Node) *enode.Node {
// RequestENR does not yet support context. It will simply time out.
// If the ENR can't be resolved, RequestENR will return nil. We don't
// care about the specific error here, so we ignore it.
nn, _ := s.p2pServer.DiscoveryV4().RequestENR(enr)
return nn
}
iter = enode.AsyncFilter(iter, resolverFunc, maxParallelENRRequests)
iter = enode.Filter(iter, eth.NewNodeFilter(s.blockchain))
iter = enode.NewBufferIter(iter, discoveryPrefetchBuffer)
s.discmix.AddSource(iter)
fairmix := enode.NewFairMix(0)
for i := 0; i < discoveryParallelLookups; i++ {
iter := s.p2pServer.DiscoveryV4().RandomNodes()
iter = enode.AsyncFilter(iter, resolverFunc, maxParallelENRRequests)
iter = enode.Filter(iter, eth.NewNodeFilter(s.blockchain))
iter = enode.NewBufferIter(iter, discoveryPrefetchBuffer)
fairmix.AddSource(iter)
}
s.discmix.AddSource(fairmix)
}

// Add DHT nodes from discv5.
if s.p2pServer.DiscoveryV5() != nil {
filter := eth.NewNodeFilter(s.blockchain)
iter := enode.Filter(s.p2pServer.DiscoveryV5().RandomNodes(), filter)
iter = enode.NewBufferIter(iter, discoveryPrefetchBuffer)
s.discmix.AddSource(iter)
fairmix := enode.NewFairMix(0)
for i := 0; i < discoveryParallelLookups; i++ {
iter := s.p2pServer.DiscoveryV5().RandomNodes()
iter = enode.Filter(iter, eth.NewNodeFilter(s.blockchain))
iter = enode.NewBufferIter(iter, discoveryPrefetchBuffer)
fairmix.AddSource(iter)
}
s.discmix.AddSource(fairmix)
}

return nil
Expand Down