Opentelemetry Baggage Propagation

[rachelyangdog]

What does this PR do?

• I've added support for propagating baggage on the only http client-side integration (net/http’s roundtripper.go)
• I've added support for propagating baggage for most server-side HTTP integrations (the ones that use httptrace.go to generate their spans)
• I've added "baggage" as part of the default propagators

Motivation

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.
• For internal contributors, a matching PR should be created to the v2-dev branch and reviewed by @DataDog/apm-go.

Unsure? Have a question? Request a review!

[datadog-datadog-prod-us1]

Datadog Report

Branch report: rachel.yang/baggage-prop
Commit report: 76bd3f5
Test service: dd-trace-go

✅ 0 Failed, 5246 Passed, 73 Skipped, 2m 1.97s Total Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-02-13 19:45:19

Comparing candidate commit 3c6ea6d in PR branch rachel.yang/baggage-prop with baseline commit c345adb in branch main.

Found 1 performance improvements and 6 performance regressions! Performance is the same for 55 metrics, 0 unstable metrics.

scenario:BenchmarkHttpServeTrace-24

• 🟥 allocated_mem [+307 bytes; +335 bytes] or [+3.193%; +3.481%]
• 🟥 allocations [+10; +10] or [+12.346%; +12.346%]
• 🟥 execution_time [+1.047µs; +1.171µs] or [+6.430%; +7.194%]

scenario:BenchmarkSetTagMetric-24

• 🟩 execution_time [-4.445ns; -2.715ns] or [-3.619%; -2.210%]

scenario:BenchmarkStartRequestSpan-24

• 🟥 allocated_mem [+8 bytes; +8 bytes] or [+3.226%; +3.226%]
• 🟥 allocations [+1; +1] or [+16.667%; +16.667%]
• 🟥 execution_time [+48.549ns; +49.431ns] or [+13.374%; +13.617%]

[mtoffl01]

On the right track, but the new code in StartRequestSpan is causing us to do tracer.Extract twice when we could just do it once. At the same place where we process span links after trace extract (line 127 on your branch, currently), we can also populate a baggagemap with the baggage items found from the returned spanParentCtx. Then, we can push those items onto the request context that we are going to propagate after line 141.

[darccio]

LGTM. Approving this, given @mtoffl01 is going to be applied too.

[mtoffl01]

Approved, but with the following notes:

1. Update the PR title
2. Update the PR description to specify what exactly is in scope in this PR. In short, you've added support for propagating baggage with HTTP headers in net/http client and all http integrations that use httptrace.go to generate their spans. More info in this little doc I put together: https://docs.google.com/document/d/1Te1L6QKzQpbtNMqe_KD3YXPTzcP-AZCSUJ44NlVNHII/edit?tab=t.0

[rachelyangdog]

/merge

[dd-devflow]

View all feedbacks in Devflow UI.
2025-02-13 18:45:09 UTC ℹ️ Start processing command /merge

---

2025-02-13 18:45:17 UTC ℹ️ MergeQueue: pull request added to the queue

The median merge time in main is 0s.

---

2025-02-13 19:01:46 UTC 🚨 MergeQueue: This merge request is in error

mergequeue build completed successfully, but the github api returned an error while merging the pr.
It's probably because:

• target branch of PR is restricted to only allow up-to-date branches, but the pr is now outdated

Details

Error: PUT https://api.github.com/repos/DataDog/dd-trace-go/pulls/3126/merge: 405 5 of 5 required status checks are expected. []

FullStacktrace:
activity error (type: github.GithubService_MergePullRequest, scheduledEventID: 41, startedEventID: 42, identity: 1@github-worker-575b699795-26xsc@): PUT https://api.github.com/repos/DataDog/dd-trace-go/pulls/3126/merge: 405 5 of 5 required status checks are expected. [] (type: GitFailure, retryable: false): PUT https://api.github.com/repos/DataDog/dd-trace-go/pulls/3126/merge: 405 5 of 5 required status checks are expected. [] (type: ErrorResponse, retryable: true)