feat(internal/log/telemetry): add SDK error-reporting API for Error Tracking

[darccio]

Summary

• Auto-forward sink: hooks internal/log.Error so every non-rate-limited call is mirrored to instrumentation telemetry. The format string is the constant dedup key; variadic error args are scrubbed via NewSafeError; a redacted stack trace is always attached. No change to local log output.
• Policy table (internal/telemetry/log/policy.go): single place to classify format templates as report / downgrade (→ warn) / exclude. Pre-seeded with agent-connectivity and user-misconfiguration noise.
• Explicit helpers (internal/telemetry/log/helpers.go): ReportError(msg, err, opts...) for swallowed errors; ReportPanic(recovered, msg) for recover() sites. Both enforce the constant-message contract.
• constantlogmsg analyzer (internal/telemetry/log/analyzer/): go vet-compatible pass that rejects non-constant message arguments. Standalone binary for go vet -vettool; make lint/errlog target added.

Test plan

• go build ./... — no compile errors
• go vet ./internal/log/... ./internal/telemetry/log/... — clean
• go test ./internal/log/... ./internal/telemetry/log/... -count=1 -race — all green (17 new tests)
• make lint/errlog — no violations in existing codebase
• No import cycle introduced (internal/log does not import internal/telemetry/log)
• Local log output unchanged (verified by TestErrorLocalOutputUnchanged)

Reviewer notes

• The sink is registered via init() in forward.go; it is active whenever any code imports internal/telemetry/log. Existing uses of log.Error require no changes — the auto-forward handles them. Non-constant first arguments will be flagged by the new analyzer.
• The policyTable in policy.go is intentionally sparse. Prompt 2 (migration) will populate it as call sites are classified.
• The analyzer uses fake package paths in testdata (bypasses the internal import restriction) and a New([]FuncSpec) constructor for test-scoped configuration.

Related epic: APMLP-1503

[datadog-prod-us1-6]

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 78.62%
• Overall Coverage: 62.87% (+11.49%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: e9d5965 | Docs | Datadog PR Page | Give us feedback!}

[pr-commenter]

Benchmarks

Benchmark execution time: 2026-07-10 15:51:12

Comparing candidate commit e9d5965 in PR branch dario.castane/hungry-einstein-959818 with baseline commit 1d87e06 in branch main.

Found 2 performance improvements and 5 performance regressions! Performance is the same for 318 metrics, 1 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 ----------------------------------'

scenario:BenchmarkMetrics/distribution/get-handle

• 🟥 execution_time [+3.183ns; +4.177ns] or [+2.538%; +3.331%]

scenario:BenchmarkOTLPProtoSize/1000spans

• 🟥 execution_time [+21.039µs; +23.526µs] or [+6.660%; +7.447%]

scenario:BenchmarkOTLPProtoSize/100spans

• 🟥 execution_time [+2.223µs; +2.447µs] or [+7.045%; +7.755%]

scenario:BenchmarkOTLPProtoSize/10spans

• 🟥 execution_time [+220.497ns; +251.103ns] or [+6.828%; +7.775%]

scenario:BenchmarkOTLPProtoSize/1span

• 🟥 execution_time [+26.878ns; +30.542ns] or [+6.917%; +7.860%]

scenario:BenchmarkPayloadVersions/simple_1000spans/v1.0

• 🟩 allocated_mem [-1 bytes; -1 bytes] or [-2.857%; -2.857%]

scenario:BenchmarkPayloadVersions/simple_100spans/v1.0

• 🟩 execution_time [-391.011ns; -345.589ns] or [-2.483%; -2.194%]

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

[kakkoyun]

We should remove these files and make the new analyzer includes the functionality https://github.com/DataDog/dd-trace-go/blob/main/rules/telemetry_rules.go and https://github.com/DataDog/dd-trace-go/blob/main/rules/logging_rules.go