Add warn log for OTel top-level spans change

[liustanley]

What does this PR do?

Adds a warn log in trace agent for top-level spans change in this PR: #22163. This is intended to bring more visibility since this is a potential breaking change for OTel customers.

The logs appear as follows:

2024-03-28 11:25:13 EDT | TRACE | INFO | (pkg/trace/api/api.go:207 in Start) | Listening for traces at http://localhost:8126
2024-03-28 11:25:13 EDT | TRACE | DEBUG | (pkg/trace/stats/concentrator.go:151 in Run) | Starting concentrator
2024-03-28 11:25:13 EDT | TRACE | DEBUG | (pkg/trace/api/otlp.go:96 in Start) | Listening to core Agent for OTLP traces on internal gRPC port (http://localhost:5003, internal use only). Check core Agent logs for information on the OTLP ingest status.
2024-03-28 11:25:13 EDT | TRACE | WARN | (pkg/trace/api/otlp.go:99 in Start) | OTLP ingest identifies top-level spans by span kind which may impact trace metrics. This feature can be disabled by adding 'disable_otlp_compute_top_level_by_span_kind' in DD_APM_FEATURES.

Motivation

Additional Notes

Possible Drawbacks / Trade-offs

Describe how to test/QA your changes

Run trace agent with OTLP ingest enabled and verify the new warn log shows.

[pr-commenter]

Test changes on VM

Use this command from test-infra-definitions to manually test this PR changes on a VM:

inv create-vm --pipeline-id=31030108 --os-family=ubuntu

[pr-commenter]

Regression Detector

Regression Detector Results

Run ID: 566d473b-60a4-44bc-bdca-9e138c8ab7b8
Baseline: b238404
Comparison: 12f2e23

Performance changes are noted in the perf column of each table:

• ✅ = significantly better comparison variant performance
• ❌ = significantly worse comparison variant performance
• ➖ = no significant change in performance

No significant changes in experiment optimization goals

Confidence level: 90.00%
Effect size tolerance: |Δ mean %| ≥ 5.00%

There were no significant changes in experiment optimization goals at this confidence level and effect size tolerance.

Experiments ignored for regressions

Regressions in experiments with settings containing erratic: true are ignored.

perf	experiment	goal	Δ mean %	Δ mean % CI
➖	file_to_blackhole	% cpu utilization	-0.14	[-6.42, +6.15]

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI
➖	tcp_syslog_to_blackhole	ingress throughput	+1.12	[+1.03, +1.21]
➖	file_tree	memory utilization	+0.50	[+0.41, +0.60]
➖	process_agent_standard_check	memory utilization	+0.14	[+0.09, +0.19]
➖	idle	memory utilization	+0.11	[+0.08, +0.14]
➖	process_agent_real_time_mode	memory utilization	+0.08	[+0.04, +0.11]
➖	tcp_dd_logs_filter_exclude	ingress throughput	+0.01	[-0.03, +0.05]
➖	uds_dogstatsd_to_api	ingress throughput	-0.00	[-0.20, +0.20]
➖	trace_agent_msgpack	ingress throughput	-0.01	[-0.02, +0.00]
➖	trace_agent_json	ingress throughput	-0.05	[-0.08, -0.02]
➖	process_agent_standard_check_with_stats	memory utilization	-0.12	[-0.16, -0.08]
➖	otel_to_otel_logs	ingress throughput	-0.12	[-0.54, +0.30]
➖	file_to_blackhole	% cpu utilization	-0.14	[-6.42, +6.15]
➖	pycheck_1000_100byte_tags	% cpu utilization	-0.92	[-5.82, +3.97]
➖	uds_dogstatsd_to_api_cpu	% cpu utilization	-1.51	[-4.36, +1.33]
➖	basic_py_check	% cpu utilization	-2.19	[-4.64, +0.25]

Explanation

A regression test is an A/B test of target performance in a repeatable rig, where "performance" is measured as "comparison variant minus baseline variant" for an optimization goal (e.g., ingress throughput). Due to intrinsic variability in measuring that goal, we can only estimate its mean value for each experiment; we report uncertainty in that value as a 90.00% confidence interval denoted "Δ mean % CI".

For each experiment, we decide whether a change in performance is a "regression" -- a change worth investigating further -- if all of the following criteria are true:

1. Its estimated |Δ mean %| ≥ 5.00%, indicating the change is big enough to merit a closer look.

2. Its 90.00% confidence interval "Δ mean % CI" does not contain zero, indicating that if our statistical model is accurate, there is at least a 90.00% chance there is a difference in performance between baseline and comparison variants.

3. Its configuration does not mark it "erratic".

[liustanley]

/merge

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[liustanley]

/merge

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/remove

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[liustanley]

/merge

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