chore(config): migrate serviceName

[mtoffl01]

What does this PR do?

Migrates tracer to use Config.serviceName instead of its local serviceName.
Note that this PR is narrowly scoped; in the future, we can get rid of setting service name on globalconfig altogether, and likely stop passing in the service name to other products, as these products/packages will just query the Config singleton directly.

Motivation

Go config revamp

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!

[mtoffl01]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat(config): Config Visibility - report telemetry about all config sources #4247
• migrate ciVisibilityEnabled #4293
• chore(config): migrate serviceName #4292 👈 (View in Graphite)
• chore(config): migrate retryInterval #4240
• chore(config): migrate serviceMappings #4281
• chore(config): migrate featureFlags #4280
• chore(config): migrate env #4279
• chore(config): migrate version #4278
• chore(config): migrate hostname #4271
• chore(config): migrate logDirectory #4267
• chore(config): migrate statsComputationEnabled #4265
• chore(config): migrate noDebugStack #4264
• chore(config): migrate spanTimeout #4263
• chore(config): migrate debugAbandonedSpans #4262
• chore(config): migrate dynamicInstrumentationEnabled #4261
• chore(config): migrate partialFlushMinSpans #4260
• chore(config): migrate partialFlushEnabled #4259
• chore(config): migrate first chunk tracer configs #4258
• chore(config): migrate globalSampleRate and introduce configProvider.getFloatWithValidator #4257
• chore(config): migrate logToStdout and isLambdaFunction #4256
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-12-19 16:24:45

Comparing candidate commit 5d9df19 in PR branch 12-17-migrate_servicename with baseline commit 87da5e8 in branch mtoff/retryInterval.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 3 metrics, 0 unstable metrics.

[datadog-official]

⚠️ Tests

✨ Fix all issues with Cursor

⚠️ Warnings

🧪 1 Test failed

❄️ Known flaky: Test from github.com/DataDog/dd-trace-go/v2/internal/orchestrion/_integration/gorilla_mux (Datadog) (Fix with Cursor)

Failed

=== RUN   Test
    generated_test.go:17: Running setup
    agent.go:78: mockagent: starting
    agent.go:34: mockagent: handling request: /info
    agent.go:44: mockagent: handler not implemented for path: /info
    generated_test.go:17: Running test
    agent.go:103: mockagent: fetching spans
    agent.go:34: mockagent: handling request: /v0.4/traces
...

ℹ️ Info

❄️ No new flaky tests detected

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 5d9df19 | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

[hannahkm]

Given that we have gotten rid of the call to getDDorOtelConfig above, why don't we have to use ConfigProvider here?

[genesor]

We're using the ConfigProvider here, the internalConfig is built using the ConfigProvider and then assigned as an attribute of t.config the ServiceName in the internalConfig is picked amongst all possible sources.