misc/metrics: Expose bytes send/received per protocol

[mxinden]

Description

Expose Prometheus metrics counting the number of bytes send and received on streams per protocol.

Rough idea:

libp2p_bytes { direction = "in", protocol = "/ipfs/kad/1.0.0" } 42
libp2p_bytes { direction = "out", protocol = "/ipfs/kad/1.0.0" } 42

Motivation

Allows us to get an intuition of the bandwidth consumption of each of the libp2p protocols.

Requirements

1. Use fix(libp2p): Don't specify monorepo dev dependencies by version #3261
2. Implement Collector trait from src/collector: Introduce Collector abstraction prometheus/client_rust#82

Open questions

Are you planning to do it yourself in a pull request?

Not any time soon. Help is much appreciated.

[thomaseizinger]

Do you have a vision for how to implement this without adding a dependency onto prometheus directly to libp2p-swarm?

[mxinden]

We can use #3180 in combination with the upcoming Prometheus Collector abstraction prometheus/client_rust#82.

[thomaseizinger]

#3180 did not introduce a separation per stream though only a sum across all streams. Also, I am not yet sure how we will be able to associate the protocol with the stream because that one is only available before we inject it into the ConnectionHandler at a point where the stream has already been handed off from the muxer.