Use bytes::Bytes as the HTTP request body in HttpClient.

[mstyura]

This will allow pooling of buffers on caller side compared to usage of Vec.

Fixes

Lack of possibility to reuse buffers which are consumed by HttpClient after request has been sent.

Design discussion issue

Should old function be kept with deprecated annotation and hence new function had to have a different name or should I just introduce breaking change by changing signature of a function?

Changes

I propose to change type of body of http request accepted by HttpClient trait from Vec<u8> to bytes::Bytes.
This should unblock pooling of buffers which can be used both for serialization & being http request bodies.
Something like this (pseudo-code to get the idea):

async fn export(&mut self, batch: Vec<SpanData>) -> ExportResult  {
    let mut buffer = pool.get();
    let request = self.build_request(&mut buffer, batch);
    let res = send_request(client, request);
    pool.return(buffer);
    res
}

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 15 lines in your changes missing coverage. Please review.

Project coverage is 79.6%. Comparing base (17cce83) to head (d898ccb).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
opentelemetry-http/src/lib.rs	0.0%	6 Missing ⚠️
opentelemetry-otlp/src/exporter/http/logs.rs	0.0%	2 Missing ⚠️
opentelemetry-otlp/src/exporter/http/metrics.rs	0.0%	2 Missing ⚠️
opentelemetry-otlp/src/exporter/http/trace.rs	0.0%	2 Missing ⚠️
opentelemetry-zipkin/src/exporter/uploader.rs	0.0%	2 Missing ⚠️
...try-sdk/src/trace/sampler/jaeger_remote/sampler.rs	0.0%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #2485     +/-   ##
=======================================
- Coverage   79.6%   79.6%   -0.1%     
=======================================
  Files        118     118             
  Lines      22464   22467      +3     
=======================================
  Hits       17897   17897             
- Misses      4567    4570      +3     

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[mstyura]

Hello @cijothomas
Could you please take a look at this PR once you have time?
Thanks a lot in advance!

[lalitb]

LGTM. I believe it is safe to have dependency on Bytes crate (as of now, it was only used for header injection), as it well maintained, and widely used (eg, by tokio, reqwest, and hyper).

[mstyura]

And actually Bytes was already used in as type of response body :)

[mstyura]

Is there anything I can do to facilitate merging this?

[cijothomas]

Is there anything I can do to facilitate merging this?

Sorry for the delay! Missed this un-intentionally!

Would you be sending a PR to do buffer pooling for otlp?

[mstyura]

I don't have prepared PR to implement pooling for oltp, I've planned to implement it for Datadog (in contrib repo), because I have app which uses Datadog exporter and I see in profiler it will benefit if pooling. Regarding oltp I could try implementing it, but not very soon.

[cijothomas]

I think Datadog now supports OTLP natively, so you should be able to leverage OTLP Exporter. We were discussing the possibility of sunsetting the DD exporter in favor of OTLP (can't find that discussion anymore :( )

@scottgerring @julianocosta89 shared this doc : https://www.datadoghq.com/blog/monitor-rust-otel/

[julianocosta89]

I think Datadog now supports OTLP natively, so you should be able to leverage OTLP Exporter. We were discussing the possibility of sunsetting the DD exporter in favor of OTLP (can't find that discussion anymore :( )

@scottgerring @julianocosta89 shared this doc : https://www.datadoghq.com/blog/monitor-rust-otel/

Hello hello, just for reference, this thread had the initial discussion: https://cloud-native.slack.com/archives/C03GDP0H023/p1737396437600899