feat(internal/config): Introduce internal config package #4064

mtoffl01 · 2025-10-22T20:48:48Z

What does this PR do?

This is a POC of the "Go Config Revamp" detailed here.

Creates a new internal/config package which initializes a Config singleton once, on startup. The fields on this Config type are populated from the following sources, in order of priority: Managed Declarative Config, Datadog Env vars, Otel Env vars, and local Declarative Config. Defaults are defined as a fallback when no source has been configured for the field.

Config has been populated with a few starter fields and a few starter getters, with more to come as tracer, profiler, and other products migrate over to using the internal config as their source of truth for configuration. A single configuration DD_TRACE_DEBUG has been migrated over from tracer to internal/config, which proves that the concept works.

Motivation

See: Problem Statement
Configuration was disorganized and spread out across the repo.

Reviewer tips

Reviewers should focus on the config.go and configprovider.go files, as this is new code.

The ConfigSource implementations have been pulled from preexisting code in dd-trace-go. So, you can review these files with a little less scrutiny:

otelenvconfigsource pulled from ddtrace/tracer/otel_dd_mappings.go, but the corresponding tests are new
declarativeconfigsource and its tests were pulled from the stableconfig package
envconfigsource is quite straightforward

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 ./scripts/lint.sh locally.
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.

Unsure? Have a question? Request a review!

…ct, ConfigSource object, and tests

pr-commenter · 2025-10-22T20:52:10Z

Benchmarks

Benchmark execution time: 2025-11-13 20:43:15

Comparing candidate commit 9e109e8 in PR branch mtoff/config-revamp with baseline commit 9db3a3d in branch main.

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

…bled

datadog-official · 2025-10-24T18:16:59Z

⚠️ Tests

⚠️ Warnings

❄️ 2 New flaky tests detected

TestWriter_Flush_MultipleEndpoints from github.com/DataDog/dd-trace-go/v2/internal/telemetry/internal (Datadog)

Failed

=== RUN   TestWriter_Flush_MultipleEndpoints
    writer_test.go:242: 
        	Error Trace:	/home/runner/work/dd-trace-go/dd-trace-go/internal/telemetry/internal/writer_test.go:242
        	Error:      	Should not be zero, but was 0
        	Test:       	TestWriter_Flush_MultipleEndpoints
==================
Read at 0x00c0001121f8 by goroutine 23:
  github.com/DataDog/dd-trace-go/v2/internal/telemetry/internal.TestWriter_Flush_MultipleEndpoints()
...

TestWriter_Flush_Success from github.com/DataDog/dd-trace-go/v2/internal/telemetry/internal (Datadog)

Failed

=== RUN   TestWriter_Flush_Success
==================
Read at 0x00c00038018f by goroutine 45:
  github.com/DataDog/dd-trace-go/v2/internal/telemetry/internal.TestWriter_Flush_Success()
      /home/runner/work/dd-trace-go/dd-trace-go/internal/telemetry/internal/writer_test.go:138 +0x4f1
  testing.tRunner()
      /opt/hostedtoolcache/go/1.24.10/x64/src/testing/testing.go:1792 +0x225
  testing.(*T).Run.gowrap1()
...

ℹ️ Info

🧪 All tests passed

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

🔗 Commit SHA: 9e109e8 | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

…T_TIMEOUT DD_TRACE_LOG_TO_STDOUT DD_TRACE_PROFILER_ENDPOINTS DD_TRACE_PROFILER_HOTSPOTS DD_TRACE_RUNTIME_METRICS DD_TRACE_RUNTIME_METRICS_V2 DD_TRACE_SEND_RETRIES DD_TRACE_SPAN_TIMEOUT

…_test.go

…tead

…ty behavior of the methods

…o just Config instead of GlobalConfig

…test

Introduce internal config package: Config object, ConfigProvider obje…

b05560c

…ct, ConfigSource object, and tests

mtoffl01 added 3 commits October 24, 2025 13:58

Introduce envconfigsource, and add configprovider tests for all sources

3393771

Test migrating tracer.config.debug over to internal/config.IsDebugEna…

0bb66a1

…bled

nits

e34de5d

mtoffl01 added 19 commits October 27, 2025 11:42

fix test env vars; only use real settings

8bdab95

restore unrelated files to their status on main

0513a96

restore unrelated files to their status on main

ee521b4

Fix file format in supported_configurations.json

c3c69fe

cleanup/nits

eeebfd1

Fix references to fake configs: DD_TRACE_HOSTNAME DD_TRACE_HTTP_CLIEN…

0e2527e

…T_TIMEOUT DD_TRACE_LOG_TO_STDOUT DD_TRACE_PROFILER_ENDPOINTS DD_TRACE_PROFILER_HOTSPOTS DD_TRACE_RUNTIME_METRICS DD_TRACE_RUNTIME_METRICS_V2 DD_TRACE_SEND_RETRIES DD_TRACE_SPAN_TIMEOUT

remove reference to DD_RUNTIME_METRICS

85ae251

Introduce otelenvconfigsource, and add tests for it in configprovider…

2e5e8e6

…_test.go

Remove DD_TRACE_AGENT_TIMEOUT; use DD_TRACE_STARTUP_LOGS in tests ins…

378f08d

…tead

Make loadConfig threadsafe

7d873f4

Add godocs to loadConfig() and GlobalConfig() to document thread safe…

f148316

…ty behavior of the methods

Merge branch 'main' into mtoff/config-revamp

6c45c9a

merge main and remove refs to DD_TRACE_AGENT_PROTOCOL

4057354

Fix c.debug assignment in tracer config

bfdaae7

Always reload config in testing environment

2595c88

Fix otel test that expects panic

2fe6e13

Report telemetry in configprovider

d4960bb

Report telemetry adn add tests

0be643e

Introduce ResetConfigForTesting to reset sync.Once in tests; rename t…

b9fbb65

…o just Config instead of GlobalConfig

mtoffl01 mentioned this pull request Nov 13, 2025

Use DD_TRACE_DEBUG as telemetry key for golang, instead of trace_debug_enabled DataDog/system-tests#5709

Draft

6 tasks

mtoffl01 added 3 commits November 13, 2025 15:09

Add tests for envconfigsource and otelenvconfigsource

02802f3

Use all stableconfigsource_test logic in new declarativeconfigsource_…

ca38794

…test

Add missing cpwright headers; run go fmt

9e109e8

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feat(internal/config): Introduce internal config package #4064

feat(internal/config): Introduce internal config package #4064

mtoffl01 commented Oct 22, 2025 •

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What does this PR do?

Motivation

Reviewer tips

Reviewer's Checklist

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Benchmarks

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mtoffl01 commented Oct 22, 2025 •

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