[backport] [testutil] add flake testing marker #22028

[clarkb7]

What does this PR do?

backport flake.Mark https://github.com/DataDog/datadog-agent/pull/22028 as pre-req for https://github.com/DataDog/datadog-agent/pull/22931

Motivation

Additional Notes

Possible Drawbacks / Trade-offs

Describe how to test/QA your changes

[pr-commenter[bot]]

Bloop Bleep... Dogbot Here

Regression Detector Results

Run ID: f109a53c-5570-49cf-9eed-c2bf2c7be3d2 Baseline: 8e469e7ac753bee404fb6433c77106cf4dea5afe Comparison: b110eef0b2fa4847294ca2314d9638f2bdcbf4a2 Total CPUs: 7

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
➖	idle	memory utilization	+0.76	[+0.71, +0.80]
➖	file_to_blackhole	% cpu utilization	+0.69	[-5.87, +7.24]
➖	file_tree	memory utilization	+0.29	[+0.16, +0.42]

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI
➖	otel_to_otel_logs	ingress throughput	+1.57	[+0.85, +2.29]
➖	idle	memory utilization	+0.76	[+0.71, +0.80]
➖	file_to_blackhole	% cpu utilization	+0.69	[-5.87, +7.24]
➖	file_tree	memory utilization	+0.29	[+0.16, +0.42]
➖	process_agent_standard_check	memory utilization	+0.28	[+0.21, +0.36]
➖	process_agent_standard_check_with_stats	memory utilization	+0.14	[+0.09, +0.19]
➖	process_agent_real_time_mode	memory utilization	+0.10	[+0.04, +0.15]
➖	trace_agent_msgpack	ingress throughput	+0.03	[+0.02, +0.05]
➖	trace_agent_json	ingress throughput	+0.02	[-0.01, +0.04]
➖	uds_dogstatsd_to_api	ingress throughput	+0.00	[-0.03, +0.03]
➖	tcp_dd_logs_filter_exclude	ingress throughput	+0.00	[-0.05, +0.05]
➖	tcp_syslog_to_blackhole	ingress throughput	-0.67	[-0.74, -0.60]

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".

[clarkb7]

/merge

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