Enable resource manager metrics by default

[sukunrt]

We have found these metrics very useful and the cost of reporting metrics is not a lot. Users can opt out if they want to. In line with the rest of the places in libp2p we should enable these metrics by default too.

[marten-seemann]

Sounds good to me, let's do it!

[sukunrt]

The current implementation of TraceReporter is in a separate package github.com/libp2p/go-libp2p/p2p/host/resource-manager/obs which depends on rcmgr package.

So from within rcmgr there is no way to initialise a new StatsTraceReporter.

There are two options here:

1. Move obs.StatsTraceReporter to the same package. This would be a breaking change
2. Add a methods like Init on rcmgr which is called while setting up BasicHost

I lean towards 1 since users using StatsTraceReporter don't need to pass it explicity after this any way.

[MarcoPolo]

Can you do 1 without a breaking change? I.e both ways work

[sukunrt]

@MarcoPolo I think I can. Can you check #2388 and #2389 ?

I've moved the type StatsTraceReporter to rcmgr package and created an alias in package obs to the this rcmgr type like

package obs 

type StatsTraceReporter = rcmgr.StatsTraceReporter

kubo works fine with this. I think this should be fine.

[marten-seemann]

Can you do 1 without a breaking change? I.e both ways work

Why? This is only used by Kubo and Lotus (and maybe a very small number of consumers). I'd rather do the right thing, instead of creating additional API surface for the sake of backwards compatibility.

[MarcoPolo]

Why? This is only used by Kubo and Lotus (and maybe a very small number of consumers). I'd rather do the right thing, instead of creating additional API surface for the sake of backwards compatibility.

I'd argue that the right thing is avoiding unnecessary breakages for users. They've already jumped through the hoops of setting this up once, let's not force a harder upgrade for them.

[marten-seemann]

Building in backwards compatibility comes with a long-term maintenance cost for us. Since we're creating the PRs for Kubo and Lotus anyway, there's no cost for them to pay in the first place.

If we want to avoid breaking users, we should at least deprecate the option that we don't want people to use any more.

[marten-seemann]

#2388 deprecated the obs package, so this should be fine.

[marten-seemann]

Fixed by #2389.