Support Prometheus target metrics

[GeorgeHahn]

What does this PR do?

Adds support for scraping target metrics in the Prometheus/OpenMetrics format. Only counters and gauges are supported.

Motivation

Support better visibility into target applications

Related issues

SMP-492

Additional Notes

• Needs rebase

[github-actions]

Regression Detector Results

Run ID: 15e41a9a-4130-4608-ae4d-fb8a8b960ee5
Baseline: 2251295
Comparison: 8221417
Total lading-target CPUs: 4

Explanation

A regression test is an integrated performance test for lading- target in a repeatable rig, with varying configuration for lading- target. What follows is a statistical summary of a brief lading- target run for each configuration across SHAs given above. The goal of these tests are to determine quickly if lading-target performance is changed and to what degree by a pull request.

The table below, if present, lists those experiments that have experienced a statistically significant change in mean optimization goal performance between baseline and comparison SHAs with 90.00% confidence OR have been detected as newly erratic. Negative values mean that baseline is faster, positive comparison. Results that do not exhibit more than a ±5.00% change in their mean optimization goal are discarded. An experiment is erratic if its coefficient of variation is greater than 0.1. The abbreviated table will be omitted if no interesting change is observed.

No interesting changes in experiment optimization goals with confidence ≥ 90.00% and |Δ mean %| ≥ 5.00%.

Fine details of change detection per experiment.

experiment	goal	Δ mean	Δ mean %	confidence	baseline mean	baseline stdev	baseline stderr	baseline outlier %	baseline CoV	comparison mean	comparison stdev	comparison stderr	comparison outlier %	comparison CoV	erratic	declared erratic
blackhole_from_apache_common_http	ingress throughput	-8.18MiB/CPU-s	-0.71	100.00%	1.13GiB/CPU-s	42.28MiB/CPU-s	558.52KiB/CPU-s	0.0	0.036449	1.12GiB/CPU-s	39.29MiB/CPU-s	519.11KiB/CPU-s	0.0	0.034115	False	False
apache_common_http_both_directions_this_doesnt_make_sense	ingress throughput	-18.61MiB/CPU-s	-1.65	100.00%	1.1GiB/CPU-s	50.41MiB/CPU-s	665.88KiB/CPU-s	0.0	0.044781	1.08GiB/CPU-s	68.36MiB/CPU-s	902.91KiB/CPU-s	0.0	0.061742	False	False

[blt]

Very cool.