feat: trace context propagation behavior by igoragoli · Pull Request #4635 · DataDog/dd-trace-go

igoragoli · 2026-04-03T09:56:45Z

What does this PR do?

Implements DD_TRACE_PROPAGATION_BEHAVIOR_EXTRACT for dd-trace-go.

See RFC.

Three modes:

continue (default): existing behavior -- incoming trace context is used as the local trace context. Baggage is propagated.
restart: starts a new trace with a fresh trace ID and sampling decision. The incoming context is referenced via a span link with reason=propagation_behavior_extract. Baggage is propagated.
ignore: discards the entire incoming trace context. Returns nil, nil from Extract() so callers produce a fresh root span with no parent, no span links, and no baggage.

When DD_TRACE_PROPAGATION_EXTRACT_FIRST=true is combined with restart, baggage is explicitly extracted after the first propagator returns, since the RFC requires baggage to be propagated in restart mode regardless.

Motivation

See RFC: Trace Context Propagation Extraction Modes
System-tests PR: DataDog/system-tests#6757

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.

Note: Still working on it: DataDog/system-tests#6757

There is a benchmark for any new code, or changes to existing code.

Note: Benchmarking is explicitly out of scope per the RFC ("the processing overhead is minimal in comparison to the rest of the context extraction operation").

If this interacts with the agent in a new way, a system test has been added.
New code is free of linting errors. You can check this by running make lint locally.
New code doesn't break existing tests. You can check this by running make test locally.
Add an appropriate team label so this PR gets put in the right place for the release notes.
All generated files are up to date. You can check this by running make generate locally.
Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild. Make sure all nested modules are up to date by running make fix-modules locally.

Unsure? Have a question? Request a review!

codecov · 2026-04-09T09:45:09Z

Codecov Report

❌ Patch coverage is 91.66667% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.57%. Comparing base (fb4f2a1) to head (3243ac6).

Files with missing lines	Patch %	Lines
ddtrace/tracer/textmap.go	91.30%	4 Missing and 2 partials ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
ddtrace/tracer/spancontext.go	`93.76% <100.00%> (ø)`
ddtrace/tracer/telemetry.go	`89.15% <100.00%> (ø)`
ddtrace/tracer/textmap.go	`84.57% <91.30%> (ø)`

... and 452 files with indirect coverage changes

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

pr-commenter · 2026-04-09T10:02:37Z

Benchmarks

Benchmark execution time: 2026-05-27 12:58:09

Comparing candidate commit 3243ac6 in PR branch augusto/trace-context-propagation-extraction-modes with baseline commit fb4f2a1 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 297 metrics, 2 unstable metrics, 1 flaky benchmarks without significant changes.

Explanation

This is an A/B test comparing a candidate commit's performance against that of a baseline commit. Performance changes are noted in the tables below as:

🟩 = significantly better candidate vs. baseline
🟥 = significantly worse candidate vs. baseline

We compute a confidence interval (CI) over the relative difference of means between metrics from the candidate and baseline commits, considering the baseline as the reference.

If the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD), the change is considered significant.

Feel free to reach out to #apm-benchmarking-platform on Slack if you have any questions.

More details about the CI and significant changes

You can imagine this CI as a range of values that is likely to contain the true difference of means between the candidate and baseline commits.

CIs of the difference of means are often centered around 0%, because often changes are not that big:

---------------------------------(------|---^--------)-------------------------------->
                              -0.6%    0%  0.3%     +1.2%
                                 |          |        |
         lower bound of the CI --'          |        |
sample mean (center of the CI) -------------'        |
         upper bound of the CI ----------------------'

As described above, a change is considered significant if the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD).

For instance, for an execution time metric, this confidence interval indicates a significantly worse performance:

----------------------------------------|---------|---(---------^---------)---------->
                                       0%        1%  1.3%      2.2%      3.1%
                                                  |   |         |         |
       significant impact threshold --------------'   |         |         |
                      lower bound of CI --------------'         |         |
       sample mean (center of the CI) --------------------------'         |
                      upper bound of CI ----------------------------------'

Known flaky benchmarks

These benchmarks are marked as flaky and will not trigger a failure. Modify FLAKY_BENCHMARKS_REGEX to control which benchmarks are marked as flaky.

Known flaky benchmarks without significant changes:

scenario:BenchmarkOTLPTraceWriterFlush

- Rename firstExtract → firstExtraction - Remove extractedCtx2/ctx2 aliases, use extractedCtx/ctx directly - Improve comments explaining W3C/Datadog parent ID resolution - Improve overrideDatadogParentID docs explaining reparentID purpose

…EXTRACT

… happy path with no indents

…nStart to generate a new traceID and span ID

datadog-official · 2026-04-15T06:16:38Z

Tests

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 91.43%
• Overall Coverage: 61.86% (+3.74%)

_{This comment will be updated automatically if new data arrives.

🔗 Commit SHA: 3243ac6 | Docs | Datadog PR Page | Give us feedback!}

…_configurations

…lper, move baggage fix inside restart branch

…orExtract

spiliopoulos · 2026-05-14T19:10:29Z

👋 from a DD customer at figma. Can we do anything to help this PR along?

…-modes

kakkoyun · 2026-05-19T10:54:29Z

👋 from a DD customer at figma. Can we do anything to help this PR along?

@spiliopoulos Thanks for chiming in. We will do our best to push this forward.

@igoragoli @genesor Do you need any help with this?

genesor · 2026-05-19T14:52:16Z

Heya @kakkoyun @spiliopoulos

This PR is a mentorship project with @igoragoli, we will work on having it merged by EOW.

Once merged it will either land in v2.9.0 (ongoing release) or have to wait for the next v2.10.0 release (june)

…-modes

…y test keys

…t Extract path

…VIOR_EXTRACT

…pan link

…-modes

darccio

LGTM

spiliopoulos · 2026-05-28T14:57:30Z

Thanks for the work @igoragoli and @genesor. We will wait to see what release picks it up and give it a spin. I do expect this will give us a lot of flexibility in decomposing our traces into more manageable chunks

igoragoli force-pushed the augusto/trace-context-propagation-extraction-modes branch from 547e777 to b2227f3 Compare April 9, 2026 09:41

igoragoli added 14 commits April 15, 2026 08:12

feat: start naively adding support for DD_TRACE_PROPAGATION_BEHAVIOR_…

721ee34

…EXTRACT

feat: check allowed values

ec9d1fd

feat: make it elegant

7166cb4

refactor: start removing inline func() from Flags assignment

a31dfe1

refactor: finish removing inline func() from Flags assignment

e5d5cf4

docs: improve explanations on Extract() about propagation modes, keep…

d502c97

… happy path with no indents

chore: remove notes we don't need anymore

e74e765

fix: trace priority bug

6344be5

feat: set the restart SpanContext's baggageOnly to true to signal spa…

dad691e

…nStart to generate a new traceID and span ID

chore: regen supported configurations

502e5fc

test: add test drafts

c1876e6

chore: (PLEASE REVERT) add _context

69414fc

chore: add references to important files

e86bc01

igoragoli force-pushed the augusto/trace-context-propagation-extraction-modes branch from b2227f3 to e86bc01 Compare April 15, 2026 06:12

igoragoli added 11 commits April 15, 2026 10:39

feat: report propagation_behavior_extract in telemetry, fix supported…

b3d13f8

…_configurations

test: add unit tests for DD_TRACE_PROPAGATION_BEHAVIOR_EXTRACT

b856236

fix: propagate baggage when extract-first and restart modes are combined

abc8508

chore: document remaining work and system-tests requirements

3b072e0

chore: answer open questions in notes

13b2517

chore: format

f240849

test: update tests

9857535

refactor: clean up Extract() — remove TODO, extract extractBaggage he…

0e1e163

…lper, move baggage fix inside restart branch

chore: remove TODO above overrideDatadogParentID

7aef04e

chore: remove redundant test comment

564bc64

chore: untrack _context, keep locally

acbd99a

igoragoli added 4 commits April 28, 2026 22:21

test: compare full trace ID on echotrace_test's TestPropagationBehavi…

972ea99

…orExtract

chore: remove stray empty line

2668dfb

fix: restart with baggageOnly

7a1bf2b

refactor: format

5daff63

Merge branch 'main' into augusto/trace-context-propagation-extraction…

db24ca9

…-modes

genesor and others added 10 commits May 22, 2026 16:29

Merge branch 'main' into augusto/trace-context-propagation-extraction…

b89330a

…-modes

Merge branch 'main' into augusto/trace-context-propagation-extraction…

f8eb2e7

…-modes

chore(internal/env): regenerate supported_configurations to drop stra…

ebf781d

…y test keys

fix(ddtrace/tracer): silence checklocks on baggageOnly read in restar…

558896c

…t Extract path

fix(internal/env): use implementation B for DD_TRACE_PROPAGATION_BEHA…

7cf5ae6

…VIOR_EXTRACT

fix(ddtrace/tracer): report actual extracting propagator in restart s…

ae8049c

…pan link

chore: trigger CI

13b059c

chore: trigger CI

b2e6c85

Merge branch 'main' into augusto/trace-context-propagation-extraction…

6175178

…-modes

chore: trigger CI

3243ac6

darccio approved these changes May 27, 2026

View reviewed changes

genesor approved these changes May 28, 2026

View reviewed changes

rarguelloF approved these changes May 28, 2026

View reviewed changes

gh-worker-dd-devflow-36fce6 Bot added mergequeue-status: queued mergequeue-status: in_progress and removed mergequeue-status: queued labels May 28, 2026

gh-worker-dd-mergequeue-cf854d Bot merged commit 74d3c06 into main May 28, 2026
191 checks passed

gh-worker-dd-devflow-36fce6 Bot removed the mergequeue-status: in_progress label May 28, 2026

gh-worker-dd-mergequeue-cf854d Bot deleted the augusto/trace-context-propagation-extraction-modes branch May 28, 2026 14:11

gh-worker-dd-devflow-36fce6 Bot added the mergequeue-status: done label May 28, 2026

skang-figma mentioned this pull request Jun 2, 2026

feat: add DD_TRACE_PROPAGATION_BEHAVIOR_EXTRACT support DataDog/dd-trace-rb#5849

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feat: trace context propagation behavior#4635

feat: trace context propagation behavior#4635
gh-worker-dd-mergequeue-cf854d[bot] merged 58 commits into
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What does this PR do?

Motivation

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