perf(discv5): boost bootstrap lookups

[emhane]

Fills the three buckets at log2distance furthest from the local node id, at 5 second intervals, at bootstrap. This gives RLPx a better chance of finding peers instantly after bootstrapping.

[joshieDo]

lgtm

would one second be too noisy? Ideally we would keep the aggressive discovery until we we connect to a peer in our chain, but can be done later on, I'm not even sure if we do that for discv4

[emhane]

lgtm

would one second be too noisy? Ideally we would keep the aggressive discovery until we we connect to a peer in our chain, but can be done later on, I'm not even sure if we do that for discv4

this is stats I have so far, from RLPx peering. all started clean (without a known_peers.json file, and new non-default port).

#7683
reverses start lookup target (start filling buckets at log2distance furthest away from local node first)

on this branch
run 1

run 2

clearly this pr is better for bootstrapping, it makes a successful outgoing RLPx connection within 5 mins. think we only need to do the pulses for 100 counts (with 5 sec sleeps, 100 counts amount to 20 mins, logs show bootstrap count down becomes zero from 14:33:55 to 14:55:25). after that, main doesn't perform better than this branch in making outgoing RLPx connections.

we can expose the bootstrap pulse interval and the countdown in cli in a separate pr, then we can try 1 second like that

[emhane]

hm, we could move the bootstrap pulse out of the loop, and stack them on top of each other without sleep, let me try that

[emhane]

hm, we could move the bootstrap pulse out of the loop, and stack them on top of each other without sleep, let me try that

tried this, it's not good. the queries need some time in-between so that the next query can use the returned peers from the last query, 5 seconds seems good.

thought query_parallelism in discv5 would be handled at a higher level, but it's actually handled inside each query, not among queries. so doesn't work if they aren't executed more or less sequentially.