switch tokio-util from log to tracing

[guswynn]

Motivation

I am trying to remove any usage of log in our dep tree, so I can turn off the tracing-log feature, and I noticed tokio-util still used log, so I am trying to change it to tracing!

Solution

There were only a few callsites using log in tokio-util, so I figured switching them to tracing, like the rest of the tokio ecosystem would be fine!

[hawkw]

...I had forgotten tokio-util even had any logging in it!

[guswynn]

@hawkw I think I need to it to v0.1.25 to pass ci? that should be semver compatible with 0.1.31 (what we use in our repo) right?

[hawkw]

@hawkw I think I need to it to v0.1.25 to pass ci? that should be semver compatible with 0.1.31 (what we use in our repo) right?

yeah should be fine

[hawkw]

lgtm!

my one remaining concern is "what happens to users who expect log to work?" --- perhaps we should enable the tracing/log feature by default, but i don't love that either...

[hawkw]

<3

[guswynn]

I don't love enabling tracing/log either, especially because disabling it would need to go through tokio in some cases (or, one would have to change all the things that depend on tokio-util in your dep tree

brings up a good question: is what log backend you use protected by semver? I am inclined to say no, as there is no actual clean way to track this, but a reasonable answer might be "trace and debug log lines aren't, as they are below the default INFO level of both log and tracing"

one other option is to default to log, and then add a tracing feature, off by default, and additive-features means end users can at least do the weird thing of "depend on some library in your binary's Cargo.toml just to turn on a feature"
additive features seemed to work well here: fede1024/rust-rdkafka#440

[guswynn]

adding an optional feature was my plan for reqwest and some other crates, but I figured the fact that these are trace and in the tokio umbrella meant a hard cut was okay

[Darksonn]

I'm okay with doing this.

[guswynn]

@Darksonn as ci is passing, can this be merged?

[hawkw]

seems good to me!