Metrics dependencies are always pulled via protocol features

[thomaseizinger]

I am not sure if there is much we can do about it but I noticed that libp2p-metrics is automatically pulled in if any of the protocols that activate metrics features are activated.

When trying to upgrade to the most recent rust-libp2p HEAD, I saw libp2p-metrics come in as a dependency even though we are not specifying it as a feature. I suspect it is being pulled in by cargo due to ping activating libp2p-metrics/ping.

rust-libp2p/Cargo.toml

Line 47 in 6d3ab8a

ping = ["libp2p-ping", "libp2p-metrics/ping"]

Is there a way of how we can design this differently? Perhaps having a dedicated metrics feature within each protocol would solve this?

[mxinden]

Good catch!

Corresponding upstream tracking issue (weak dependency feature): rust-lang/cargo#8832

As far as I can tell there is no solution to this today.

I don't it hurts much, given that libp2p-metrics is a pretty light-weight dependency. Still it would be great to not pull it in each time e.g. when the ping feature is set.

[thomaseizinger]

Thanks for pointing me to that, I had no idea that this is being worked on! Very exciting :)

[mxinden]

If I am not mistaken, this can be fixed with Rust 1.60. Anyone interested in sending a patch?

https://blog.rust-lang.org/2022/04/07/Rust-1.60.0.html

[maschad]

Hey @mxinden I've added a patch in this PR. Lmk what you think.

[mxinden]

Closing here, since fixed by @maschad 🎉