Upgrade Tokio to v1

[mraerino]

Fixes #420

I also upgraded these dependencies:

• reqwest
• hyper
• tonic
• prost

[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ Marcus Weiner (891efd5, 8203e4b, 8f83db1, 8f46dc0)

[mraerino]

the minimum supported rust version for tokio is 1.45: https://github.com/tokio-rs/tokio#supported-rust-versions

do you think we could raise the version here as well? 1.42 seems pretty old

[codecov]

Codecov Report

Merging #421 (0f562c3) into master (777fdb9) will decrease coverage by 2.80%.
The diff coverage is 58.33%.

@@            Coverage Diff             @@
##           master     #421      +/-   ##
==========================================
- Coverage   51.55%   48.74%   -2.81%     
==========================================
  Files          65       66       +1     
  Lines        5117     5438     +321     
==========================================
+ Hits         2638     2651      +13     
- Misses       2479     2787     +308     

Impacted Files	Coverage Δ
opentelemetry-otlp/src/span.rs	3.26% <0.00%> (-30.08%)	⬇️
opentelemetry/src/lib.rs	100.00% <ø> (ø)
opentelemetry/src/sdk/trace/provider.rs	75.51% <ø> (ø)
opentelemetry/src/util.rs	18.30% <42.85%> (ø)
opentelemetry/src/sdk/trace/span_processor.rs	81.97% <100.00%> (ø)
opentelemetry/src/context.rs	32.02% <0.00%> (-0.22%)	⬇️

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[TommyCpp]

do you think we could raise the version here as well? 1.42 seems pretty old

I think we can. We promised three versions before current stable version, which is 1.49. So we can bump our minimum supported version to 1.45 or 1.46

[mraerino]

This is ready for a review now.
I expect this to need a major version bump since a feature flag changed and people can't update automatically via semver since they need to upgrade their tokio version too

[jtescher]

@mraerino thanks for working on this, as far as MSRV is concerned we could go either way, for example the async-std feature currently doesn't support 1.42 either. Maybe we should just remove the tokio support from the "supported" features for 1.42 and the associated ci workflow and bump it in a subsequent PR? Nice to support folks on older versions in the more stable core even if opt-in features can't support them.

Also pre-1.0 minor changes often include breaking changes, so not as much of a problem there until we hit GA

[mraerino]

Maybe we should just remove the tokio support from the "supported" features for 1.42 and the associated ci workflow and bump it in a subsequent PR?

tokio is used in the tests even if zero features are enabled. i don't think what you propose is possible with the current CI flow

[djc]

Maybe we should just remove the tokio support from the "supported" features for 1.42 and the associated ci workflow and bump it in a subsequent PR? Nice to support folks on older versions in the more stable core even if opt-in features can't support them.

Alternatives:

• Remove tokio (and probably also async-std) from the core crate (as discussed in Move integration code out of the main opentelemetry crate #403)
• Keep an opentelemetry branch alive for a bit longer with 0.11.x maintenance releases

The reason I hadn't done the upgrade here is there are also some tonic dependencies, and tonic support for tokio 1 has not yet been released. So if we want to prevent spawning multiple runtimes in the background, this PR should (a) wait until tonic 0.4 has been released -- judging from chat activity, this should come pretty soon, or (b) change crates depending on tonic to depend on a released version of opentelemetry, sticking to tokio 0.2 for now.

(Otherwise the changes here look good to me; my one nit is the underscore in the tokio_support feature flag, where I feel hyphens are probably more common.)

[mraerino]

thanks for pointing out tonic! totally did not see that.
the PR is merged so once they release it we can move forward: hyperium/tonic#530

[mraerino]

i made #424 to test the otlp exporter closer to reality. With that test, CI would be red here right now since tonic fails to run in a Tokio v1 executor.

[djc]

FYI, tonic 0.4 has been released.

[mraerino]

yup, i saw. merging master and upgrading tonic

[djc]

Other than the nit below, this is looking good to me!

[mraerino]

@djc @jtescher is there a timeline for releasing this?

[jtescher]

ASAP