pkg/trace/api: add additional fields to info endpoint.

[knusbaum]

What does this PR do?

This commit exposes additional configuration information from the Trace Agent through the info endpoint.

Motivation

We need some additional configuration info from the Trace Agent in order to support client-side stats.

Additional Notes

Possible Drawbacks / Trade-offs

Describe how to test/QA your changes

Check the output of the info endpoint to make sure:

• Peer tags are present when peer tag aggregation is enabled.
• Span kinds are present when span kind aggregation is enabled.
• client_drop_p0s is false when probability sampler is enabled.

[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=44512439 --os-family=ubuntu

Note: This applies to commit 3adfa13

[pr-commenter]

Regression Detector

Regression Detector Results

Run ID: 9ae97b78-253d-4450-8150-76dfa8d60490 Metrics dashboard Target profiles

Baseline: e7715df
Comparison: 85afa6a

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.

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	basic_py_check	% cpu utilization	+3.24	[+0.42, +6.06]	1	Logs
➖	pycheck_lots_of_tags	% cpu utilization	+1.43	[-1.23, +4.09]	1	Logs
➖	file_tree	memory utilization	+0.53	[+0.42, +0.65]	1	Logs
➖	uds_dogstatsd_to_api_cpu	% cpu utilization	+0.42	[-0.35, +1.19]	1	Logs
➖	idle	memory utilization	+0.40	[+0.36, +0.45]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	+0.00	[-0.00, +0.00]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	-0.00	[-0.01, +0.01]	1	Logs
➖	tcp_syslog_to_blackhole	ingress throughput	-0.10	[-0.15, -0.05]	1	Logs
➖	otel_to_otel_logs	ingress throughput	-0.45	[-1.27, +0.37]	1	Logs

Bounds Checks

perf	experiment	bounds_check_name	replicates_passed
❌	idle	memory_usage	5/10

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".

[VianneyRuhlmann]

As @pierotibou suggested in the design doc, the ProbabilisticSampler field could be replaced by a more generic name and the logic to enabled trace dropping could be moved in the agent.

[knusbaum]

/merge

[dd-devflow]

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[dd-devflow]

🚂 MergeQueue: pull request added to the queue

The median merge time in main is 23m.

Use /merge -c to cancel this operation!