discovery: Allow delta for create time check

[vitkyrka]

What does this PR do?

The current time checks sometimes fail due to a one second diff in the expected and actual values.

The value returned by proc.CreateTime() can vary between invocations since the BootTime (used internally in proc.CreateTime()) can vary when the version of BootTimeWithContext which uses /proc/uptime is active in gopsutil (either on Docker, or even outside of it due to a bug fixed in v4.24.8: https://github.com/shirou/gopsutil/commit/aa0b73dc6d5669de5bc9483c0655b1f9446317a9).

This is due to an inherent race since the code in BootTimeWithContext substracts the uptime of the host from the current time, and there can be in theory an unbounded amount of time between the read of /proc/uptime and the retrieval of the current time. Allow a 10 second diff as a reasonable value.

Motivation

Additional Notes

Possible Drawbacks / Trade-offs

Describe how to test/QA your changes

[pr-commenter[bot]]

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=44453259 --os-family=ubuntu

Note: This applies to commit 69626eb8

[pr-commenter[bot]]

Regression Detector

Regression Detector Results

Run ID: 008cc7a5-07f9-48a4-b0e4-fba0b896e6a8 Metrics dashboard Target profiles

Baseline: 816693f1296c07b202e401c6bbb6eb5a15ca1dd9 Comparison: 69626eb8b47b8607dec78494ccc6b646437c2082

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
➖	uds_dogstatsd_to_api_cpu	% cpu utilization	+1.14	[+0.37, +1.91]	1	Logs
➖	otel_to_otel_logs	ingress throughput	+0.49	[-0.33, +1.31]	1	Logs
➖	file_tree	memory utilization	+0.29	[+0.18, +0.40]	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
➖	idle	memory utilization	-0.31	[-0.35, -0.27]	1	Logs
➖	pycheck_lots_of_tags	% cpu utilization	-0.47	[-3.06, +2.11]	1	Logs
➖	tcp_syslog_to_blackhole	ingress throughput	-0.65	[-0.70, -0.60]	1	Logs
➖	basic_py_check	% cpu utilization	-1.28	[-4.12, +1.57]	1	Logs

Bounds Checks

perf	experiment	bounds_check_name	replicates_passed
❌	idle	memory_usage	7/10

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".

[vitkyrka]

/merge

[dd-devflow[bot]]

:steam_locomotive: MergeQueue: pull request added to the queue

The median merge time in main is 23m.

Use /merge -c to cancel this operation!