refactor(config): add cross-product gate to prevent conflicting programmatic overrides by mtoffl01 · Pull Request #4640 · DataDog/dd-trace-go

mtoffl01 · 2026-04-06T20:14:13Z

What does this PR do?

Adds a cross-product gate to internal/config that prevents different products (tracer, profiler, etc.) from setting conflicting values for the same configuration field via programmatic APIs. When a conflict is attempted, a new telemetry metric config.product_conflict is emitted.

Every Set* method now accepts an optional ...Product parameter. When a product passes its identity (e.g. ProductTracer), the gate records that claim. If a different product later tries to set the same field, the call is rejected (first-in-wins) and a warning is logged.

Env vars, defaults, and non-programmatic origins bypass the gate entirely.
Tests and integrations omit the product parameter and are unaffected.

Motivation

Previously, each product (tracer, profiler, etc) loaded configuration independently from all sources and stored its own local copy. Programmatic APIs like tracer.WithService or profiler.WithEnv would overwrite only that product's local copy. As we consolidate into a single shared Config instance in internal/config, programmatic APIs from different products now write to the same fields. The gate ensures these writes don't silently conflict: the first product to claim a field via programmatic API owns it, and attempts from other products are rejected with a warning.

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.
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 · 2026-04-06T20:19:18Z

Codecov Report

❌ Patch coverage is 51.72414% with 56 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.73%. Comparing base (bfe344a) to head (5733188).
⚠️ Report is 22 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/config/config.go	48.14%	31 Missing and 25 partials ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
ddtrace/tracer/option.go	`85.00% <100.00%> (-2.28%)`	⬇️
internal/config/config.go	`62.06% <48.14%> (+3.22%)`	⬆️

... and 269 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.

datadog-datadog-prod-us1 · 2026-04-06T20:19:50Z

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage (details)
• Patch Coverage: 36.47%
• Overall Coverage: 60.09% (+3.91%)

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

🔗 Commit SHA: 4d980f7 | Docs | Datadog PR Page | Was this helpful? React with 👍/👎 or give us feedback!}

pr-commenter · 2026-04-06T20:37:24Z

Benchmarks

Benchmark execution time: 2026-04-09 20:39:13

Comparing candidate commit 4d980f7 in PR branch mtoff/crossproduct-gate with baseline commit bfe344a in branch main.

Found 1 performance improvements and 0 performance regressions! Performance is the same for 215 metrics, 8 unstable metrics.

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 ----------------------------------'

scenario:BenchmarkParallelMetrics/rate/handle-reused-25

🟩 execution_time [-8.485ns; -1.725ns] or [-11.102%; -2.256%]

hannahkm · 2026-04-08T21:25:02Z

internal/config/config.go

 	if c.serviceMappings == nil {
 		c.serviceMappings = make(map[string]string)
 	}
 	c.serviceMappings[from] = to


Is there a reason why we don't need to check for a "conflict" here too?

See: https://github.com/DataDog/dd-trace-go/pull/4640/changes#r3058535000

hannahkm · 2026-04-08T21:27:27Z

internal/config/config.go

-func (c *Config) SetFeatureFlags(features []string, origin telemetry.Origin) {
+func (c *Config) SetFeatureFlags(features []string, origin telemetry.Origin, product ...Product) {
 	c.mu.Lock()
 	if c.featureFlags == nil {


Similar question/confirmation as below: what if c.featureFlags is not nil and contains some of the same keys as what we're adding? Since we're not checking for existing flags, it'll prioritize flags that come later?

This is a good catch, but the behavior is intentional.

The cross-product gate prevents two products from disagreeing on a single, conflicting value (e.g., service name). By contrast, feature flags and service mappings are "additive" configs — each call adds entries to a shared collection rather than replacing a value, so there's no conflict to guard against.

I've added tests to showcase this behavior in 5733188

hannahkm · 2026-04-08T21:33:22Z

internal/config/config.go

+		return false
+	}
+	p := product[0]
+	if prev, exists := c.overrides[field]; exists && prev.product != p {


Can c.overrides be nil? Should we also check and initialize it to an empty map like we are elsewhere?

It can never be nil because I initialize it to an empty map in the Config initialization ;)

kakkoyun · 2026-04-09T15:09:43Z

internal/config/config.go

+// The product parameter is variadic for ergonomic pass-through from Set* methods;
+// only the first value is used and callers should pass at most one.
+// Must be called while c.mu is held.
+func (c *Config) productConflict(field string, origin telemetry.Origin, value any, product ...Product) bool {


I think it reflects more correctly what this function does.

Suggested change

func (c *Config) productConflict(field string, origin telemetry.Origin, value any, product ...Product) bool {

func (c *Config) checkProductConflict(field string, origin telemetry.Origin, value any, product ...Product) bool {

hannahkm

LGTM!

Introduce productConflict logic, tests, and update README

813b378

mtoffl01 requested review from a team as code owners April 6, 2026 20:14

mtoffl01 marked this pull request as draft April 6, 2026 20:14

mtoffl01 added 3 commits April 8, 2026 12:29

cleanup & introduce telemetry counter for config product conflict

5a715db

remove benchmark txt file

ca22512

Only consider conflicting values as a product conflict

8eb44c0

mtoffl01 marked this pull request as ready for review April 8, 2026 18:49

hannahkm reviewed Apr 8, 2026

View reviewed changes

Add tests and docs for additive configs

5733188

kakkoyun reviewed Apr 9, 2026

View reviewed changes

rename productConflict -> checkProductConflict

4d980f7

mtoffl01 requested review from hannahkm and kakkoyun April 10, 2026 14:17

hannahkm approved these changes Apr 10, 2026

View reviewed changes

mtoffl01 merged commit f9776f2 into main Apr 10, 2026
117 checks passed

mtoffl01 deleted the mtoff/crossproduct-gate branch April 10, 2026 17:36

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refactor(config): add cross-product gate to prevent conflicting programmatic overrides#4640

refactor(config): add cross-product gate to prevent conflicting programmatic overrides#4640
mtoffl01 merged 6 commits intomainfrom
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	func (c *Config) productConflict(field string, origin telemetry.Origin, value any, product ...Product) bool {
	func (c *Config) checkProductConflict(field string, origin telemetry.Origin, value any, product ...Product) bool {

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What does this PR do?

Motivation

Reviewer's Checklist

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Benchmarks

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scenario:BenchmarkParallelMetrics/rate/handle-reused-25

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