swarm/: Set dial concurrency factor default value to > 1

[mxinden]

Description

I propose increasing the default dial concurrency factor to some value larger than 1.

You can use https://kademlia-exporter.max-inden.de/d/Pfr0Fj6Mk/rust-libp2p (bottom) to determine how many addresses nodes advertise for the various libp2p networks.

Also worth checking what go-libp2p uses as a default value.

Motivation

Dialing addresses of a single dial concurrently gives a significant improvement in latency.

Feature was introduced in #2404.

Default value is set here:

rust-libp2p/swarm/src/connection/pool.rs

Lines 1164 to 1165 in 8361fab

	// By default, addresses of a single connection attempt are dialed in sequence.
	dial_concurrency_factor: NonZeroU8::new(1).expect("1 > 0"),

//CC @dignifiedquire who has recently stumbled across this.

[maschad]

For some reason I am getting a 502 on the Grafana dashboard

But it seems that go-libp2p uses a dial concurrency factor of 8 if I'm not mistaken, it could be one of the other constants though as the terms are a bit convoluting.

[mxinden]

Sorry, kademlia-exporter.max-inden.de has some uptime issues currently. Posting a screenshot here for now:

But it seems that go-libp2p uses a dial concurrency factor of 8 if I'm not mistaken, it could be one of the other constants though as the terms are a bit convoluting.

Seems to be right 👍

[maschad]

Kademlia seems to be back up now, I created a PR #2741

[mxinden]

Closing here with #2741 merged.